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Posted by: malcolm2 Apr 25 2023, 01:53 PM

Hello everyone. I will preface by saying that this is an engine from a 914.

But it is in my VW Bus. Just now getting it moving down the road. Everything is new.

Carbs are new and I am a carb rookie, as well. Bought them from Aircooled.net and had them cleaned and set-up for the bus. My 914 has L-Jet FI, this group has taught me enough about that system to be dangerous.

So here is my question for the carb experts. What should the Pump Valve spray look like? It seems erratic and drippy. It kicks in 1st as I open the throttle, not a spray but pore, really. I will say that I see that in all 4.

Posted by: malcolm2 Apr 25 2023, 04:35 PM

Maybe the video will help. Close to the end, not very good lite, but the pump jets seem to really be flowing..... Is that normal. All 4 are doing it.

The purpose of the video was about the idle dropping, hence the name, but I got distracted by what seemed to be excess fuel.


https://www.youtube.com/watch?v=_4lPU2DNt44

Posted by: nditiz1 Apr 25 2023, 06:07 PM

So John from ACN is a master with carbs. Buying his clean and tune service is very valuable as well as his knowledge with IDFs.

It looks like either the accel pump linkage is not set properly, a blockage, OR missing parts. You should have a good steady stream squirt when you activate the throttle. I would pull the carbs off and check the stream on the bench. Also, pull open the pump on the side and make sure the spring is in there. It's been so long I cannot remember the base setting for the pump rod, but I want to say 3 threads showing after the lock nut.

Posted by: r_towle Apr 25 2023, 06:59 PM

Sounds like they are not synced.
One cylinder sounds off, with valve noise also.

Even at revving it still sounds off.

I believe these are new carbs, you stated you just bought them?
Start with remove and verify all settings.
Sadly, they won’t be the same
Check and fix float level
Check and fix accel pump settings.

You should not see fuel at idle
Yes you will see the pumps squirt when you blip the throttle…they is their job
You should not see them at constant higher rpm’s ( to a point)

Get the book on how to tune webers.
Syncing them , once you get it right, will make the engine purr

Posted by: r_towle Apr 25 2023, 07:02 PM

What carb linkage are you using?
Have you adjusted valves recently ( it does not sound like it)

You can tune each barrel to really be perfect.

Posted by: Superhawk996 Apr 25 2023, 08:16 PM

To answer your question on the second carb it seems more normal. You should get a pretty steady stream. It will not be any sort of “spray” that is atomized coming out of the nozzle.

The first view the engine is shaking around too much (sign of not being synched) that I can’t see it terrible clearly but it does sort of look like too many drops and not enough stream

I agree with Nditiz - probably want to check them and figure out why you’re not getting a stronger stream.

Both the nozzle and the check valve are tunable to get the volume of accelerator pump discharge you need. However, you need that accelerator pump spring adjusted correctly and you need to make sure the pump diaphrams are in good shape 1st.

Posted by: malcolm2 Apr 25 2023, 09:02 PM

I did adjust the valves while the engine was on the stand, and after some test running. but It would not hurt to check that again. I do have the SNAIL tester and have used it a few times.

The linkage is Sync-Link with cables and pulleys. I struggled with the hex bar and gave up on that.

Posted by: malcolm2 Apr 25 2023, 09:50 PM

Do you have a book in mind? I checked the normal sources and it seems that the reviews are generic.

Very detailed instructions came with these carbs stating how to sync them which I have been thru a few times. Planned on doing that once more.

But you and others are suggesting a bit of a deeper dive with more detail settings and measurements etc... I would prefer a book that was for these IDFs or IDF 40s specifically.

Any thoughts here?

Posted by: Superhawk996 Apr 26 2023, 06:32 AM

Don’t worry about IDF specific book. I personally like the Dellorto book but it is now out of print.

The import part is understanding:

Weber IDFs run on the idle circuit and transition ports most
Of the time at light cruise and light tip in. You really only run on the mains when RPM is high and creating lots of vacuum at the Venturi neck. You can convince yourself of this truth by driving the car with the main jets and emulsion tubes removed.

As a result, the idle circuit tuning is critical. Note: Your motor isn’t idling well based on the video. Likewise it doesn’t transition off idle well.

You need to know what size Venturi and jets you’re working with as your baseline. You won’t get a decent snappy throttle response until you get down to 28mm venturis. Most
Carb kits come with venturis that are 30-32mm (too large) for top end HP - not good driveability.

Make sure your transition ports aren’t partially uncovered at idle. I used to see this all the time. Make sure your idle speed set screw isn’t holding the throttle blades too far open and uncovering the transition ports.

You need to balance airflow between each individual barrel before synching the carbs. Each time you adjust airflow - you’ll have to go back and tweek idle mix and also idle speed.

Look around for a used copy - Amazon, Ebay, post in forum, etc

Posted by: nditiz1 Apr 26 2023, 07:30 AM

"You can convince yourself of this truth by driving the car with the main jets and emulsion tubes removed."

This is something that all carb owners should experience even triple owners. Get a feel for how the engine responds and where the drop off actually happens. Try not to perform this drive over any real big hills as it may require higher RPM/butterfly opening which will throw you into the Main and the car will want to die.

I'm going to assume that he is running a 28 venturi, 115 main, 50 idle, and 200 air if John set them up from ACN, but always good to double check.

Posted by: malcolm2 Apr 26 2023, 07:53 AM

I did see a video on youtube with a guy, IDFs and a 912. Running around a parking lot with the mains out. Very interesting. Discussion starts at about 16 minutes....

https://youtu.be/2uDY1wcx6mo

ACN sheet confirms, with one exception.

Posted by: rhodyguy Apr 26 2023, 08:00 AM

FWIW, AC.net is out of biz. Doors closed. The website did not reflect the change. The FB page is more up to date.

On the bottom of the Webers note the threaded rod. If the adj is too tight the pump jet can dribble.

Thomlinson’s Weber book is first rate. I found the Dell manual lacking.


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Posted by: malcolm2 Apr 26 2023, 08:13 AM

ACN website does leave a bit of the door open for them to return, but I think it has been more than 6mths that it has been closed.

Yes, someone mentioned the pump rod adjustment. They could not remember the setting. But is was to count the threads (probably above the nut). I think he said, like 3 threads??? This one has quite a few more.

That book is very popular, and out of stock, even on ebay. I found a HAYNES on ebay for $15. I got that coming. and a PDF version of Dellorto Tuning Manual by John Savage that I downloaded.

Posted by: rhodyguy Apr 26 2023, 08:23 AM

Can you compare the exposed threads side to side? Match the side that does not dribble.

Does the jet in ? dribble when the pump is energized and the engine is not running? If so, you might try backing the nut on the offending side off a bit.

Every time you adj something on the carbs, wait a moment for the adj to take affect. They don’t respond like FI.

What flavor of fuel pump are you using?

Posted by: malcolm2 Apr 26 2023, 08:50 AM

Just a quick fuzzy picture yielded similar threads on both carbs. 11 to 12 threads on each.

Pump is also from ACN. Do not think ROTARY is a brand. I believe Carter is a similar design. But I mounted it under the tank on the frame of the Drivers side.

Posted by: rhodyguy Apr 26 2023, 08:59 AM

2 filters? The middle canister is a filter. I got rid of it. I went with a FI filter, same sized inlet and outlet. Perfect fuel line fit. Use shouldered clamps. Easier to see when the filter is fouled. The metal can? Not so much.

Posted by: rhodyguy Apr 26 2023, 09:12 AM

Does the jet dribble when the fuel pump is energized? Have someone turn the key while you watch. Your engine oil may be contaminated with fuel. I would change the oil after you fix the dribble

Posted by: sportlicherFahrer Apr 26 2023, 09:50 AM

The Tomlinson book is on the CB Performance site as well. Currently it shows available for adding to cart, but also has the link for notify when back in stock so I'm not sure what their stock really is.

https://www.cbperformance.com/product-p/0103.htm


Also, the repackaged Carter pump retailers sell (CB, PP, AC.net, and others) is available on Amazon for about half the cost. Not sure why there's such a big markup on these from the average car sites. Carter part number P90091.

https://www.amazon.com/gp/product/B07BBDSZP1/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Posted by: rhodyguy Apr 26 2023, 09:54 AM

‘Email notification when back in stock’. Could be a long wait. Post a WTB in the classifieds.

Posted by: 930cabman Apr 26 2023, 10:08 AM

I would bet on either the pump stroke is insufficient or the pump jet is (#12) is clogged, assuming the floats are at the correct setting and the float bowls are near full.

Posted by: malcolm2 Apr 26 2023, 12:20 PM

"Product images are representative only..."

IIRC I did not get the clear filter. I do know that all the clamps are "permanent", if you will. Not the screw type, nor do they have the shoulders.

I like the FI filter idea. I have a few of those packed away for the 914, so it would be good for the Bus and the 914 to use a few interchangeable parts.

Yeah in high school, I had a bug with a metal can. Out of the blue it would just stop running..... I would wait about 30 minutes and it would start and get me where I was going. Eventually I figured out that the metal filter was clogged up and you could not see it. Sh*t never changes.

Posted by: r_towle Apr 26 2023, 02:10 PM

I used two filters on my race car because the tank was toast.

I use one on either side of the fuel pump (because filters are cheap)
the inlet filter between tank and fuel pump is a race filter, can be taken apart and cleaned. It has a stone??? in it with tons of holes used as the filter.

That was the one that I kept having to clean.
a new tank fixed my issue, but I left two filters in place because it protects the fuel pump...

I can fix any issue on the side of the road by cleaning up that race filter with some carb cleaner.....so I like that.

For the OP
Carbs do not (aside from the accel pump) squirt fuel.
Fuel is sucked into the engine by the motor, via the carbs.

So, your adjustments are three.
One, the size of the Venturi really matters...the smaller it is, the faster the suction velocity. Standard Webers are all wrong when we buy them.
Get to the 28mm vents before you get super frustrated.
It will always be a bit sluggish without doing that first step.
It will run, it can be tuned...but it will always be meh.

Suction matching on the engine is dependent upon the intake and exhaust valves being identical in adjustment over all 4 cylinders.
If one of them is wrong (one of yours is wrong...I can hear it) then the suction on that cylinder will be different from the other three.

Get the valves perfect.
Take your time....and get used to doing it.
Its not a terrible job if you learn the easy way to get it done.
I think (maybe) Cap'n Crusty did a write up on how he did it in the Classics forum here...at least I hope that still exists (RIP Cap'n)

Idle jets...
Pretty simple jet, but its the one that does a lot of the work.
Perfectly tuned at idle matters a ton.

Mains are just flood gates, when you need them (high rpms) and you won't feel them....idle is the key jet.

the Access pumps are typically setup wrong from the seller
The floats are typically setup wrong from the seller
The jets....remove and verify each on (there are tiny numbers on them)

Trust but verify.


Rich

Posted by: 914werke Apr 26 2023, 04:45 PM

Not to hijack the thread but has anyone see these installed in their Webers?


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Posted by: nditiz1 Apr 26 2023, 05:59 PM

Rich, I just check 3 sets of my carbs. All of them have that missing. The one set that I run on test engines runs fine without it.

Posted by: 914werke Apr 26 2023, 06:03 PM

Ya Ive never see it before & they are installed in a set of Italian 40's Im restoring.
It plugs a opening ..for some reason?

Posted by: sportlicherFahrer Apr 26 2023, 07:27 PM

I believe that piece is a float bowl vent that was omitted on Webers made outside Italy. No big deal if removed. If it's not plugged, it's probably okay to run as is if needed.

Posted by: malcolm2 Apr 26 2023, 10:15 PM

Pulled the plugs and did a compression check before i adjust the valves.

Plugs were BLACK. Got pix if we have any plug readers in the group.
1-2 were super black and dry.
3-4 were not as black and looked wet

Compression was
1. 100
2. 110
3. 120
4 115

Will adjust the valves again, re-check compression add some low mileage plugs and pull the carbs to verify settings and check for clogged jets and float height.

Might take a day or so, damn real job is calling.

Posted by: Superhawk996 Apr 27 2023, 07:52 AM

Black = way too rich

Definitely verify float level as 1st step.

You won’t end up with black plugs from clogged fuel Jets but could occur due to clogged air correction jets and/or air passages.

install new plugs, then go back to basics: setting idle mixture, balancing airflow, and synchronization.

Posted by: malcolm2 Apr 29 2023, 02:35 PM

update......

I have chromoly push rods and swivel foot adjusters. I have been told to adjust valves as follows.

ROTOR BUTTON pointing at #1 Attempt to rotate the swivel foot on I and E adjusters for #1. Grab the rocker and pull outward. Listen for a slight rattle.

The object here is ZERO LASH.

Bentley says to start at 1.... rotate rotor CCW to 2, then 3 then 4.


I have gone around the engine 3 times. ALL EIGHT valves allow the swivel foot to rotate (spin) and the only click I get is if the rocker moves side-to-side. I also have solid aluminum spacers with 2 warped spring washers so there is just a bit of room for the rocker to move side-to-side.

Let me know what you think. I will go around once more.... maybe video the fun and report back here.

Posted by: nditiz1 Apr 29 2023, 02:40 PM

Sounds fine.

I usually see if I can spin the pushrod and have no movement of the rocker, but your method seems to work as well.

The goal of lash is for expansion of the aluminum pushrods during run. Chromoly do not, or maybe extremely little. .006/.008 for aluminum .000 for chromoly.

Posted by: r_towle Apr 29 2023, 03:19 PM

So, I am lazy and I hate getting up and down 50 times.

Jack up car
Lower car so one wheel is resting on a 6x6
Put car in 5th

Rotate the wheel like reverse
This spins the motor forward

A valve on each side of the motor will be closed (bottom of the lobe) at the same time.
The lobe that is shared will always have one valve open and one closed.

Hard to explain but you can adjust one valve on both opposite sides of the motor at the same time.

Let me find his thread.
Found it

http://www.914world.com/bbs2/index.php?showtopic=28758

Posted by: malcolm2 Apr 29 2023, 03:43 PM

I have done it 4 times.... even getting up and down only four times. All valves allow the swivel for to spin but give no rocker movement.... all 8 are on zero lash.

Pretty much did the cap'n crusty method.

I do not feel like these valves are out of adjustment. What else can you suggest to determine if they are out of adjustment.

I did take a video of each cylinder.... I am attempting to meld the 4 videos together. Maybe it will work, maybe not. If not I will post 1 video as all four result in the same thing..... swivel foot spins with the valves closed. Glad to try something else.

Posted by: nditiz1 Apr 29 2023, 04:04 PM

Who said your valves were out? I think someone mentioned to check they are in spec.

You should be fine, continue on to adjusting the carbs. Maybe we can vid chat and I can dump all my carb knowledge.

Posted by: malcolm2 Apr 29 2023, 04:09 PM

A couple folks mentioned valve noises, now after checking them, I can believe that it may be the side to side of the rockers. That is really the only clicking I hear with these chromoly push rods.

Damn if I can remember if there was a reason.... Something came with the solid spacers and some washers. I see that I was not consistent with assembly of the washers.

They are all taking up the same amount of space, wonder if it matters. Maybe I should add more washers where I am getting the most side to side noise on adjustment??

hard to see, but IV has 4 washers in the middle. III has washers spread out. same deal on the I II side. Not consistent with the washers for some reason.

Posted by: nditiz1 Apr 29 2023, 04:38 PM

No that all seems fine. I didn't hear anything abnormal from your video except it was not running optimally due to the carbs.

The spacers will be different due to how much the valves were clearances on the sides ( I'm assuming Tabari? did them) you try to get slightly off center from the valve so it spins the valve as it hits it instead of exact center.

Posted by: porschetub Apr 29 2023, 06:22 PM

many don't check this and its essential for good valve sealing and wear on the stems.

Posted by: malcolm2 Apr 29 2023, 06:48 PM

Heads are Camper Specials from Type4store.com. They did the valves etc… as well. All the innards are from them. Cam, lifters, bearings, push rods. Probably other stuff I can’t remember.

Posted by: r_towle Apr 29 2023, 08:18 PM

After you have done this adjustment, did your compression test results change?

Posted by: malcolm2 Apr 30 2023, 05:02 AM

I did not adjust any valves. I checked each valve several times using the method described about and once using the cap’ns “rocking” method.

Each check resulted in zero lash.

Posted by: nditiz1 Apr 30 2023, 07:49 AM

Was this a newly rebuilt engine?

Compression test should be done on a warm engine. Also, I rarely do compression tests anymore even on unknown engines. I get more info from leak down tests.

Posted by: PatMc Apr 30 2023, 09:29 AM

Compression test on an engine that overfueling will not be very accurate because the fuel is washing down the cylinders. I wouldn't concern yourself with the compression numbers right now

Posted by: 930cabman Apr 30 2023, 01:43 PM

Rich, find out why. floats, mis adjustment, needle valve. So long as there is some compression the engine will run

Posted by: rhodyguy Apr 30 2023, 02:02 PM

If you verify the floats source new gaskets first. If it’s apart, get some.

Posted by: malcolm2 Apr 30 2023, 03:24 PM

Yes a 1.8 from a 914 in northern Alabama. I upped it to a 2.0 with bus pistons.

Posted by: malcolm2 Apr 30 2023, 03:42 PM

This float setting does not seem to be accurate. I see videos with the dude hold the plate vertically, the floats bounce back and forth and he sticks a mic on it and says it is not right.

Sorry, but I don't see the exact second when he is measuring a moving float.

ACN says they set mine at 12mm.... I can move the plate around and say BOOM... 12 mm. is that right? THis guy suggests 10mm. i can't tell.



https://www.youtube.com/watch?v=54uPwTZ3DJw

Posted by: malcolm2 Apr 30 2023, 04:25 PM

OK... the more i putzed with it, the more I could see where he was measuring.

Tilt floats down and they open fully.

Tilt slowly backwards and the floats will STOP moving.

Tilt more backwards and the floats touch the gasket.

I measure at the STOP point. I got just about 12mm, just like ACN said. Does this group agree that 12mm is good? the video above the dude wanted 10mm.


https://www.youtube.com/watch?v=jJ4UhNCru5s

Posted by: r_towle Apr 30 2023, 04:29 PM

10mm is correct. Not sure where 12mm came from

https://www.dellortoshop.com/contents/en-us/d2019_Weber-IDF---How-to-set-the-float-level.html

Posted by: r_towle Apr 30 2023, 04:30 PM

Curious to know the differences you find between the two carbs.

Posted by: malcolm2 Apr 30 2023, 04:40 PM

The floats on both carbs are 12mm. Post #11 has the spec sheet that ACN gave me with my carbs.

12mm from the plate to the top of the float would result in LESS fuel in the bowl than if they were set at 10mm from the float to the plate, correct?

It seems that my situation is, or might be OVER FUELING. So the bowls are LESS full per the float at 12 vs 10mm, correct?

Posted by: r_towle Apr 30 2023, 05:05 PM

In theory you are right.
The proper specification is 10mm, but you can set it as you choose.

I would suggest you verify the needle valve is seating properly with no dirt or obstruction then you are done with this step.

Remove and verify your jets are correct, and properly seated.
Then move to validate your accel pump, gaskets, settings etc.
The pump needs to be right

Posted by: r_towle Apr 30 2023, 05:06 PM

The collective experience we have all had is that new carbs are not always setup properly and you can get two carbs that are different.

Posted by: cgnj Apr 30 2023, 05:30 PM

Based on video at idle you have at least one dead hole Look how much it is rocking. Carb on 2-3 bank has pump jet circuit problem. Should look like #4

Can this car idle without blipping the throttle? If it can pull the plug wires off one at a time. Idle speed drops = good hole Move to next one. Check all of them.

Posted by: malcolm2 Apr 30 2023, 06:35 PM

I removed the floats and dropped the needle valves, I see no dirt in the needle valves. Jets have all been removed and verified with the spec sheet.

I did remove the pump cover and checked under the pump. Springs are there. It seems to activate the jets nicely on the bench.

Someone mentioned the pump adjustment is set with the threaded rod and nut, but Number of threads??? Is that the check? how many?

While on the bench, I loaded the bowls with carb cleaner and activated the throttle. The pump jets were straight and true, I saw no leakage.

Posted by: Superhawk996 Apr 30 2023, 06:36 PM

Don’t get hell bent on the exact number - people have their own preferences.

What you want to know is where is it at and is it in the ball park within a couple mm - your answer to that is yes - OK

The reason you want a baseline. Higher fuel level in the bowl from your baseline = runs richer. Lower fuel level in the bowl runs leaner.

Posted by: malcolm2 Apr 30 2023, 06:43 PM

That is why I paid extra for the "set-up" from Air Cooled.net. So going thru this exercise has confirmed that they did what they said they would do.

Posted by: Superhawk996 Apr 30 2023, 06:55 PM

I should have mentioned 10mm correlates to a higher fuel level in the bowl as you correctly inferred.

FWIW - 10mm seems too high to me. CB Performance IDF guide suggests 14mm. That seems low but again it’s all relative to what your engine wants.

You need to figure out why your plugs are black.

I’m guessing . . . but assuming . . . you don’t have idle mixture screws and throttle plate position set properly as you’re trying to tune idle. If your idle speed screw is holding the throttle blade above the 1st transition port, you’re going to pull in too much fuel at idle and lose throttle response.

Once you get closer to an ideal tune, then float level can be used to tweak slightly richer / leaner but at this point - let it go. You’re close enough.

Posted by: Superhawk996 Apr 30 2023, 07:02 PM

Since you were looking for a book and the Tomlinson books aren’t readily available - I highly recommend reading this - the Weber tuning manual that was put out by Weber.

This doesn’t have the IDFs but the way the idle circuits woek and the transition from idle to mains is the same. Pay special attention to the diagram on page 10.

https://www.lainefamily.com/images/WeberTuningManual.pdf

Posted by: Superhawk996 Apr 30 2023, 07:07 PM

So you know that isn’t the problem - go back to the tuning basics - best idle, balance airflow, sync carbs. Don’t mess with the accelerator pump linkage - if you’re spraying a steady stream on the bench - it’s OK and the issue is elsewhere.

Although I didn’t pick it up in the video - take the prior suggestion to heart that Member CGNJ mentioned. Make sure you’re running on all 4 cyclinders. That is assumed before any attempt to tune

Posted by: 930cabman May 1 2023, 10:35 AM

I run 12+mm on my 40IDF Weber floats. I prefer to have the fuel level a bit lower as opposed to higher. Is your fuel pressure in the 1 - 3 psi range? I run around 1.5 and seems to work just fine.

Posted by: malcolm2 May 1 2023, 12:13 PM

That is my next recommendation.... As I started doing test drives around the hood, it was suggested to run at 3.5 psi.

Recently, it was recommended to drop to 2.5, so once I get the carbs back on and the idle adjusted and sync'd, I will drop the pressure.

Whole thing started when I noticed the pressure was 1.5 not sure what happened with that, but since then, I have made enough changes to pretty much start from scratch.

So here I go...

Posted by: 930cabman May 1 2023, 01:37 PM

For me 1.5 works great (on the street), a track machine might be different and I have never ran the float bowls empty with 1.5 psi. Staying on the low side makes sense for me.

Posted by: porschetub May 1 2023, 11:34 PM

Posted by: malcolm2 May 3 2023, 07:48 AM

Found some time last nite and I re-assembled the carbs and set the screws as recommended in the Weber set up document. One thing I did notice is that the AIR BLEED SCREWS, marked red below, were NOT SEATED.

They were 2 maybe 3 turns OUT. all 4 were that way. I don't remember doing that, but I am sure I did.

Wouldn't more air call for more fuel? So maybe this had something to do with my Super Rich situation?

Posted by: malcolm2 May 3 2023, 07:49 AM

Posted by: Superhawk996 May 3 2023, 08:19 AM

Good find. Usually you’ll only have 1 air bleed screw adjusted per carb and even then only slightly.

Keep going - you’re on the right path!

Also make sure if your carbs are equipped with vacuum ports - they should be sealed. I’ve seen Weber IDF’s with no ports, 1 port per pair of carbs, and 1 port on each barrel. Not sure what dictated the port configurations. Regardless, they need to be sealed, either with plugs or by being connected to the distributor vacuum canister (without leakage) if you’re using vacuum advance.

Posted by: malcolm2 May 3 2023, 01:59 PM

I do have a vacuum can on the disty. Both carbs have a Vac. Advance Port as noted above. They came plugged. I removed 1 plug and attached a hose to the vac can. I also have a 1 way valve on that hose or something similar. IIRC AC.net recommended the device to help smooth out erratic pulses.

Posted by: rhodyguy May 3 2023, 02:38 PM

Tomlinsons Weber book p.22 ….’pre-set your air by-pass screws. Set them 1/2 turn off the bottom’. Beg, borrow or steal a Tomlinsons.. Start at the beginning and go thru the set-up procedure again. It’s only a few screws and settings. Should take about 10-15 minutes. Start fresh.

Posted by: nditiz1 May 3 2023, 04:54 PM

ACN recommends using the port over cyl 4. I use the anti pulse when running dual carbs as well.

I haven't cracked my Tomlinsons in awhile, but I set my air bypass the same as Richard from PMO sets his. All closed, whichever chamber is the lowest, open to bring it up. Should only need a few turns. Anything excessive and you might have a vac leak. I think you were able to sync all 4 chambers so that's probably not a problem.

Now that you have them back together, turn your car on to fill the fuel bowls. Then turn off the car and manually operate the throttles to see the squirt volume. Both sides/all 4 should have the same shot.

Posted by: malcolm2 May 4 2023, 12:14 PM

Maybe you would send it to me..... ??

I will pay the freight to and from and get it back to you ASAP.

Posted by: rhodyguy May 4 2023, 12:56 PM

PM sent.

Posted by: Jack Standz May 4 2023, 02:08 PM

The current standard specification is 12mm to 14mm (and with the float flipped the other way, it's 34mm).

Something about fuel now being part alcohol (10%). This makes the float sink a little more because current fuel is lower specific gravity. So, unless you're running 100% gasoline in the motor, you should be good.

Posted by: nditiz1 May 4 2023, 04:44 PM

I think I have an extra one for Weber, or an extra for Dells, but yeah I can send it.

Posted by: malcolm2 May 4 2023, 07:35 PM

Thanks. I bought a weber one on ebay. And i have borrowed the supertech book. I will read it and return it. No need for copies or pdfs. Wink wink.

Posted by: malcolm2 May 4 2023, 07:39 PM

I go back and forth on ethanol or pure. Nice to know why we were getting 10 and 12 from different folks.

Posted by: malcolm2 May 6 2023, 08:15 AM

OK.... engine started. Had to give the idle screws a full turn to get it to idle.... but it is running on it's own this morning.

The first thing i wanted to do was adjust the fuel pressure. it is just slightly above 3 this morning.

I did get some comments that the gauge could be troublesome. But I attempted to adjust the QFT low pressure regulator and the gauge did not move... threaded it in and out and got no change in the gauge. Did not notice any engine changes either.

EDIT::: I turned the engine off, and let the pressure bleed off and restarted and was able to ADJUST to 1.5.


But which way do i adjust the regulator? I would have thought IN would block the fuel and lower the pressure??

https://www.jegs.com/webapp/wcs/stores/servlet/SearchResultsPageCmd?q=793-30-804QFT&storeId=10001&catalogId=10002&langId=-1

Posted by: 930cabman May 6 2023, 01:48 PM

Keep us in the loop as you get her purring.

Posted by: r_towle May 6 2023, 02:28 PM

Synced ?

I’m hoping you nail it!

Rich

Posted by: malcolm2 May 6 2023, 03:12 PM

I may have..... Flow matches on all barrels, idle is set, linkage is back on and the flow #s and RPM stayed the same.

I took a video of the end and will add it here later. I am happy, but my FP gauge is still acting strange. I can't really adjust it up, but I can adjust it down.

This morning it was on 3, i took it to 1.5 and every now and then I see it drop to about zero.

Posted by: malcolm2 May 6 2023, 03:25 PM

youtube won't let me rotate..... but you can still watch. Hey, is there a way to add a DOCUMENT to a post?


https://www.youtube.com/watch?v=ofShSBhPMSo

Posted by: r_towle May 6 2023, 03:49 PM

I’m still hearing sumpin wrong.
Still sounds like one cylinder is not performing the same as the other three.
I forget what venturis you have, but you may want to get smaller ones
It seems sluggish at lower idle.
Maybe get a new fuel pressure unit?

Posted by: 930cabman May 6 2023, 05:07 PM

How does she run? WOT? seems to idle ok

Posted by: Superhawk996 May 6 2023, 05:15 PM

Still sounding a bit like it’s bogging a little when throttle begins to open before it picks up RPMs. You are on 28mm venturis so should be better than that.

I think you’re getting a bit distracted by fuel pressure. To be honest, carbs don’t care much and will run in a wide range of pressure between 1-4 psi. Don’t believe me. Try this - run your fuel pump till bowls are full - then disconnect and plug the fuel line. You’ll be amazed how long it will idle / and do light transitions before the bowls run low and start running really poorly.

You’re expecting a 0-15 psi gauge to be accurate in the 1-3 psi range. I think you’re probably seeing gauge “sticktion” at those low pressures where the needle temporarily sticks from internal gauge friction with just barely enough pressure to even begin to move the gauge. As someone said earlier you want a gauge that is about 0-5 psi to have an accurate indication.

Depending on the range that the regulator is designed for it may be that the “sticktion” is in the regulator if that was designed for 0-15 psi. Edit: just looked at your JEG’s link - you should be peachy!

Bottom line - I suspect you’re chasing your tail on fuel pressure.

Barrels to barrel airflow is pretty good. Edit: after watching a 2nd time - I’d say that one cylinder is 6 vs all the others at 6.5. Might bring that one up to 6.5 with air bypass. Then recheck idle mix.

Are you sure your idle mix is tuned properly for best lean idle? I know you said you’re about one turn out which is probably about right but you should be getting an idle speed drop if you open or close the idle mix from that setting if you’re at best lean idle. Is that the case?

What is your idle speed set at? The tach is not the best indicator if true idle speed. I use a digital engine multimeter to set idle speed. Idle sounds sort of low. Once you have best lean idle set, you should only be using the carb linkage, idle screw to tweek the idle speed. After you tweek that, you need to go back and recheck best lean idle mix - it’s an iterative loop.

Also what distributor set up are you using? You may not be getting enough advance early enough.

Final edit - I just compared 1st video to latest. Defiantly improving. Good job. Keep tweaking it and once you have the idle speed and mix finessed - go back and recheck carb to carb sync and how equally your linkages are moving. You’re getting there

Posted by: Jack Standz May 6 2023, 05:52 PM

Yes, fuel pressure could be the problem, if you truly are having little or none.

I recently had a problem where the fuel pressure gauge was showing zero and the regulator made no change to the reading turned all the way in or out. The motor would run. But, it wouldn't run right or wouldn't take a tune. Since the motor would run (some), I just couldn't believe the gauge.

Completely new fuel delivery system, new carbs, new motor. Turns out the fuel line was kinked under the tank (914 versus bus). Seems that some fuel could make it through. At least the first carb in the set was gettingsome fuel. Bus fuel lines are different, but I suppose something could pinch it.

Probably not your problem, but worth checking. Especially since you said the gauge goes to zero. But, it could be just the gauge. I bought a second gauge ($15 on Amazon) that also showed zero before I figured out the fuel line was pinched. When you get it figured out, run with 3 psi or less, as long as fuel isn't dribbling out the auxiliary venturis. My 2056 likes about 2.5 psi give or take.

If you want to tune these carbs, suggest getting a colortune spark plug (Google it) and a wide band AFR gauge (you decide whether to permanently mount it or not. If permanently mounted in a bus, you'll need the longer wiring harness.

Posted by: malcolm2 May 6 2023, 06:56 PM

All day run with new plugs. Lots of adjusting etc.. but not DRY JET BLACK.

Posted by: Superhawk996 May 6 2023, 07:15 PM

You’re running way too rich

Have you verified that the throttle plate is closed, covering the 1st transition port when the idle speed screws aren’t even touching the linkage?

This is Hugely important.

If you have done that then I suspect the idle mix isn’t being adjusted properly for best lean idle

OR

You will need to go down on idle jet size

Posted by: malcolm2 May 6 2023, 07:46 PM

Only way to verify now is that the speed screw is hitting the bracket. I did look at it when it was on the bench. Fully closed. Several little holes in the barrel under the plate. Seemed closed to me.

Remember, this pic is from idling all day and setting and resetting screws. All that. They look a bit lean to me. Gray??

Posted by: Superhawk996 May 6 2023, 11:11 PM

There are also a series of small holes (the transition ports) that should closed and a few that are open or just obscured above the plate when the throttle plates are closed.


It is critical that you’re not running idle such that the transition ports are uncovered by having the idle speed screw set too far open. You want to make sure you don’t have the condition shown in illustration B when idling.

With respect to the plug condition, that plug is no where near a lean condition even when looking at only the insulator.

Here’s a plug visual reference

Posted by: malcolm2 May 7 2023, 08:11 AM

Here is the LBI method I was using, per http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm

DO YOU SEE ANYTHING ELSE I SHOULD DO, OR DO DIFFERENTLY??

Linkage removed
Speed Screw 1/2 turn in after touching
Bypass screws closed
Mixture screws out 1 turn

Engine runs poorly as expected.
1. turn IN mix screw until the engine runs worse... i would turn each screw about 1/4, then move to the next one, and so on. 2nd time around (1/4 at a time), as I got to the 3rd barrel, the engine would run worse.
2. turn OUT mix screw until the engine runs better. Again 1/4 turn at a time, til I got no reaction. Turn them back IN until they are BEST.

Then I set the Speed screw to 950 to 1000rpm. I have an analog meter.... one lead on batt- one lead on coil-. using the V8 scale and doubling it. I am sure you remember those old timers.

I placed the snail on the front barrel of one side then the other. adjusted the High flow barrel down to the low flow barrel with the speed screw. then adjust both back to 950 -1000, matching flow using the snail.

From there, i went to the bypass screws. checking flow front barrel to back barrel and adjusting the LOW flow up to the high flow. Leaving the high flow CLOSED. Then again, matching the right to left carb's flow to the idle rpm with the speed screw.

I have a new pertronix SVDA disty with a P3 module in it. I dismantled it, and cleaned and lubed it after arrival.... another AC.net item.

Posted by: malcolm2 May 7 2023, 08:21 AM

Was thinking I should put an A/F on the bus and eventually I will.

I have a A/F on my 914. It has a blue tooth adapter that allows me to use my phone for the readout. Unfortunately, they have been out of stock for over a year. Guess I need to find another vendor....

https://www.plxdevices.com/ProductDetails.asp?ProductCode=897346002931

Posted by: Jack Standz May 7 2023, 12:16 PM

Yes, +1.

Posted by: rhodyguy May 7 2023, 12:27 PM

Now you’re seeing how small adjustments can result in BIG changes. Remember to pause a bit after every adj. Bosch plug #?

Posted by: Superhawk996 May 7 2023, 01:18 PM

Generally I think you’re on the right path and doing reasonable things. You don’t mention readjusting mixtures after resetting idle speed. Idle mix affects idle speed and vice versa. Same again after setting an air bypass - recheck mix all the way around again after that. Everything affects everything else.

I might go only 1/4 turn on the initial idle speed screw just to ensure that transition port is fully closed when you are adjusting mixture initially.

And probably just slow down on the idle mix screw adjustment - there is always some time delay between turning the screw and observing the effect when it finally gets to the engine.

Maybe smaller 1/8 turn changes as you get closer. It really is a multiple iteration process between mixture, idle speed, air bypass. Each change affects the others. Agree with Rhodyguy that small changes have big effects as you get closer and closer.

Check ignition advance and make sure you’re starting to begin a good advance by 1500 rpm. As noted on NGK chart retarded timing (not enough advance) can manifest as running rich. Basically just verify SVDA is working properly.

And finally, it isn’t unheard of to have to go down an idle jet size. Too big of a jet really jacks up the speed & mixture effects of the needle mix screw adjustments. .

Posted by: malcolm2 May 8 2023, 09:32 AM

NGK BPR6ES

Posted by: malcolm2 May 8 2023, 05:30 PM

I would not say WOT, but fast enough for me to be a bit worried.... 55mph in a bus is kinda scary. But engine-wise it felt nice.... a bit up hill, accelerating all the way thru 4th gear.

I live on a hill with 4 speed humps. The trip on the day that crap started raising it's ugly head, I did not feel like I had much power.

TODAY, I went up the hill 2 times, 2nd gear, pulling hard after the speed humps to the next hump.... also felt good. Enough power for a 72 bus with a 2.0 liter, bus pistons and camper special heads!!! Much better. Drove about 8 miles today around the hood and down to the elementary school on the long straight is where I got to 55.

Posted by: malcolm2 May 8 2023, 05:37 PM

I found a way to MAYBE verify your concern about the throttle plate and maybe you are right, but how do I deal with it? As you can see from the last vid, all 4 barrels are very close in flow. So here is what i found.








It was obvious that the tip of the speed screw shows more threads on the PASS Side than on the Drivers Side. Wouldn't that mean that there is a chance that the plate is open past the port you showed me???

What can I do to make it close more and still run nicely?

Posted by: Superhawk996 May 8 2023, 06:50 PM

I wouldn’t judge by that 1.3mm variance in the amount of screw showing. You have casting variance, stamped linkage variance, and variance in the length of the screw. That 1.3mm variance is sort of normal when you synch carb to carb.

Especially since you seem to be happy that it’s running better and improving.

I’d just stay focused on trying to lean out idle mixture and given where you are in the process, I’d just swap the idle jet and keep moving forward.

I’ve always made a point of being sure that the transition ports are closed when it is on the bench for initial bench settings. It’s much harder to do when the carbs are installed.

What I’d probably do is shine a light down the throttle bore and verify that the throttle butterfly is hardly open when it’s setting at rest on the idle speed screw stop. Throttle butterfly plates should basically be closed with only a tiny sliver of a gap. Maybe you might be able to see the top of one of the transition ports sitting ABOVE the plate that would be good. If the butterfly plates seem to be lifted significantly when sitting in the stops, I might pull them and bench check where they are sitting. Just pulling them and replacing them won’t mess up too much of the tuning you’ve done but you’ll have to verify and then re synch again.

I would really hate for you to pull them again which is why I’m suggesting you go down in idle jet 1st. It’s easier and is probably going to be more of a sure thing vs the chance that the transition port is uncovered at idle.

Posted by: r_towle May 8 2023, 07:13 PM

The throttle plates should be visible from above to let you see how they are sitting at idle.
Idle is zero throttle
They should match.

Like Stated above, the screw position can be different
The throttle plates should not be different

To make yourself comfy with how they work….I might suggest you remove the throttle linkage
Start car
Turn screw out (close throttle plates)
Listen to the difference on each side
Then check again with the air flow meter, adjust as needed.

You are getting close, and thankfully once you get them setup perfectly for your engine, you won’t need to adjust them anymore.

Get the plugs brown, not black
It can be done, and you will be thrilled once you nail it

Then you can answer all carb related questions here

I listen to the motor, your ear can tell once it purrs

Posted by: malcolm2 May 9 2023, 01:14 PM

OK so I should get smaller Weber IDF Idle Jets.... CB has 0.45 and 0.40. figured I would get 4 of each. $4.50 each.

I have 0.50

Seem correct?

https://www.cbperformance.com/product-p/6394.htm?1=1&CartID=1

Posted by: 930cabman May 9 2023, 01:20 PM

Where are your idle mixture screws? If I recall correctly they should be in the range of 1 1/2 turns out from seated. If less the idle jets are too large, if more the idle jets are too small. PLEASE check the previous statement. It's one way or the other

Don't throw new jets in her just for the heck of it

Posted by: nditiz1 May 9 2023, 01:54 PM

50 idle are fine. I doubt you will need to go lower.

Posted by: malcolm2 May 9 2023, 06:21 PM

1 is 1/2 a turn +1/8 a turn (0.625 turns)

2 is 1/2 a turn + 1/8 a turn (0.625 turns)

3 is 1-1/2 turns + 1/8 a turn (1.625 turns)

4 is 1 turn (1 turn)

after checking, i started it up and checked the flow..... all were very close to the same

Posted by: r_towle May 9 2023, 08:37 PM

You are using the idle bypass screw to make up the difference in throttle plate positioning….at least it seems to be that way

What throttle linkage do you have again?
I recall totally giving up on cross bar linkage and going to dual cable controls by Foley as the only way to tune the carbs at lower rpm’s.
The linkage geometry is really hard to get right at low rpm’s, but you can get it to work 2500-6500 rpms

Posted by: malcolm2 May 9 2023, 08:46 PM

Yes i used the air bypass as discussed above. One barrel on each side is used to match the flow on that side.

I have the cable type sync-link.

Posted by: r_towle May 9 2023, 08:48 PM

3&4 are one carb?
Not sure how you are numbering

Posted by: r_towle May 9 2023, 08:59 PM

I may be missing something, but when I start from the beginning, I do this.
Start car, run till warm
Set idle bypass screws exactly the same
Set idle arm mechanism and throttle plates exactly the same
Verify throttle plate position by measuring from top to plate with a micrometer (be accurate)

Turn it off
Disconnect throttle linkage
Start car
Adjust each barrel to match with idle bypass screw

Very gently, with no pulling or repositioning, adjust and attach throttle linkage.

Posted by: malcolm2 May 10 2023, 04:58 AM

Question from 930 Cabman was for mixture screws. The larger screws with the springs on them.

Your question was for Bypass screws, right? They were adjusted as stated and the last step: only adjusting one on each carb to match flow in each barrel on that side. Leaving one on each side closed. I don’t remember the turns there. Maybe 1-1/2 on one barrel on each side.

Those screws are smaller and have a lock nut on them.

Posted by: 930cabman May 10 2023, 05:06 AM

There are 2 idle mixture screws per carb near the bottom and 1 idle speed screw per carb.

Posted by: malcolm2 May 10 2023, 05:09 AM

Yes bypass screws were set the same. All were closed. I did not measure the throttle plate. As it was not part of weber’s Lean Idle process. Other than that, and adding the mixture screw adjustment, that is what i did.

Posted by: malcolm2 May 10 2023, 05:13 AM

Yes. Speed screw is the one on the shaft that opens the plates. Just one per carb. 1 per barrel of each: bypass screw and mixture screw. I will add a picture with all that labeled. That drawing is an idf. I have idfs.

Posted by: malcolm2 May 10 2023, 05:38 AM

top 1/2 of PAGE ONE of http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm

I will add your suggestion on the throttle plate measurement. In that case, how do you adjust one if the measurements don't match on one carb?





This is a strange document..... page one and page 2 say pretty much the same thing. But this one does have the diagram.

Posted by: 930cabman May 10 2023, 05:42 AM

I have always closed the air bypass screws and never used them for adjustments.

Posted by: malcolm2 May 10 2023, 05:43 AM

I found these posts from other forums.... this is how i set the bypass screws.

Posted by: 930cabman May 10 2023, 05:53 AM

Personally the twin Webers I have worked with have been close from barrel to barrel. I'm not sure how exact this needs to be? Within 1/2 on a snail gauge works for me.

Posted by: malcolm2 May 10 2023, 05:54 AM

the cylinders are numbered on the tin.

1 carb is on the 1-2 cylinder side, one carb is on the 3-4 side. each cylinder has a barrel in the carb, and bypass and mixture screws.

Posted by: malcolm2 May 10 2023, 06:03 AM

as for this statement about JETS..... i reported the mixture screw settings and 3 seems wonky. 4 is only a 1/4 turn more than 1 and 2.

This would not be suggesting that you use different jets on different barrels, right?


I am thinking I should start the whole process again as per the Best Lean Idle doc. I have done it about 4 times, I am getting good at it, or at least I thought I was, until I see these mixture screw results.

Posted by: Superhawk996 May 10 2023, 06:43 AM

You’ve got something a bit wonky. All 4 idle mix should be pretty close to each within about 1/4 turn to the others assuming all cylinders are pulling equivalent airflow and one of the air bypass screws hasn’t been opened too much.

Side 3/4 is different enough from 1/2 that I’d suspect both sides might not be closing the butterfly plates the same or possibly that you just have the idle speed screw turned in just a little bit too far (back to that 1.3mm delta between screws).

Over tightening the nuts that hold the end linkages to the throttle shafts can cause binding. Again, for me, this usually this gets checked on initial bench setup. I know your carbs are brand new and probably OK but I’m starting to lean toward recommending you pull them again for a good bench check now that you have a couple other things you’ve learned and can check for.

Before you do - I’m with you - go ahead and do another best idle mix. Practice makes perfect. I wish there were a magic way to tune carbs but in all honesty, you’re right on course as a beginner. I takes a while to get the hang of it. It’s all about iteration, knowing each adjustment affects the others.

Also I should have asked but assumed all 4 plugs were pretty similar to the one you posted?

See where you end up after another go-round. You made a good call ordering the other idle jets - very easy to swap and even if you ultimately end up back at .50’s, the experience of trying them, observing the changes, and how idle tuning affects drive ability is worth the price of admission into the mythical realm of carb wizardry

Posted by: malcolm2 May 10 2023, 06:57 AM

I did not pull the other plugs to see how they looked. I will do that.

On the linkage, remember, I have the cable type with pulleys.... SYNC-LINK.

https://lnengineering.com/sync-link-throttle-linkage-kit-for-weber-idf-carburetors.html

I did notice that if the nut holding the pulley is tight, the shaft does not rotate easily and smoothly. There is a tab type lock washer under that nut. So i get the nut snug and check the rotation. Snug a bit more, check again. Once I feel it affecting the throttle plate movement, I back off the nut and bend the tab. So I feel that the pulleys are snug, but not tight.

Posted by: Superhawk996 May 10 2023, 06:59 AM

A note of encouragement.

Weber’s are among the most tunable carbs in the world. There are so many things that can be changed - venturis, idle jets, main jets, emulsion tubes, air correction jets, accelerator pump metering, accelerator pump nozzles! Not to mention the air bleed screw, mixture screws, and the idle speed.

This makes them highly adaptable to almost any engine and it’s why they were used so widely back in the day by Porsche, Ferrari, Alpha, Lamborghini and so many legendary cars!

The down side is that they can be overwhelming at first. Hang in there - you’re doing great as a beginner!

Posted by: Superhawk996 May 10 2023, 07:01 AM

Perfect. You’re aware of it and managing it!

Posted by: r_towle May 10 2023, 09:12 AM

3/4 carb setup does not match 1/2 carb
Thus the wierd idle and off idle issue

Posted by: malcolm2 May 10 2023, 11:37 AM

Maybe a good measurement. But I don’t hear or feel anything. Sounds good and drives good. You guys have gotten me here. Might as well go all the way.

On the snail video, give me a time marker of what you hear.

So just to understand and maybe learn this tune by sound, i am gonna do the best lean process once more.

Posted by: rfinegan May 10 2023, 12:35 PM

post another video of how its running, after you best lean tune

Posted by: Superhawk996 May 10 2023, 11:12 PM

Original video - 9 seconds and 58 seconds

When you open the throttle you can immediately hear the engine stumble or bog down a little bit. Tone changes (lower pitch) and engine doesn’t immediately pick up RPMs. Essentially a stumble or time delay before the engine responds to your input and the engine is momentarily slowing down for those milliseconds before it recovers.

Based on that black plug, it’s running rich when idling. Then you hit the throttle and dump in even more fuel via the accelerator pump. It then takes a little bit of time for the air flow to catch up enough to lean the mix out a bit (but still rich overall) and then the RPMs can pick up.

Posted by: malcolm2 May 11 2023, 06:03 AM

Wouldn’t the original video be worthless now that i have changed settings? I guess it could help with BAD sounds.

I would be more curious about the sounds on the SNAIL video. That is current state.


Might have time to get to a full re-do this evening. You asked about the plugs. I will pull them all and and pix before i head to my real job today.

Posted by: Superhawk996 May 11 2023, 06:20 AM

Sorry, was late for me and I was tired. Those time stamps were from the video with the snail.

Yes, agree a little irrelevant if you’re readjusted and just a general comment on the what I was hearing in the early videos.

The 1st original video was worse with the engine shaking visibly much more due to poor tune and lack of synch & air balance. It got much better in the snail video but was still bogging when you initially open the throttle. Those are the time stamps I referenced.

Posted by: malcolm2 May 11 2023, 09:09 AM

Rich as expected. 1 & 2 do look better, but still have the a bit of very black non-shiney, dusty look on the edge. Kinda strange, but maybe not since each barrel is adjustable, but they all have a bit of difference.

I think 1 is best, 3 is worst, in terms of BLACK-ness.

Again, this was about an hour idling when I was adjusting, then maybe 10 miles of driving.

Can this be cleaned off to review again when I have attempted BEST LEAN IDLE?

Posted by: rhodyguy May 11 2023, 09:32 AM

3-4 are running really fat.

Posted by: r_towle May 11 2023, 09:38 AM

Reading plugs happens two ways
One at idle….
Then, after you super clean them start and drive immediately, with little to no idling
Go run it up and down the gears
When you are coming into the driveway, shut it down
Try for no idle during this phase ( not easy)
I start it and rev immediately to 2500 ish

After you stop, let it cool down
Check the plugs again
You should see a different condition

Idle is typically much richer
You want perfect color under load, when driving

Rich

Posted by: r_towle May 11 2023, 09:39 AM

Reading plugs happens two ways
One at idle….
Then, after you super clean them start and drive immediately, with little to no idling
Go run it up and down the gears
When you are coming into the driveway, shut it down
Try for no idle during this phase ( not easy)
I start it and rev immediately to 2500 ish

After you stop, let it cool down
Check the plugs again
You should see a different condition

Idle is typically much richer
You want perfect color under load, when driving

Rich

Posted by: 930cabman May 11 2023, 09:42 AM

If I am checking plugs, I will run WOT for a short time, cut the ignition, coast to a stop and look at the plugs. Idling is a small portion of the picture, I want to know the mixture under load.

Posted by: gnomefabtech May 11 2023, 11:18 AM

Big transition bogging is often caused by not enough timing advance. I couldn't see if you are using a vacuum advance but you should. Idea is that under low load and high vacuum there's a lot of advance to burn clean and under big load, less, so you don't get knock. For performance, vacuum advance should be connected to manifold vacuum NOT venturi vacuum. Set your total advance (above 4k rpm) to about 36deg with vacuum capped then let the idle advance fall where it does once the vacuum is connected.

I don't think you can read the plugs to set the idle mixture. For me the best results come from just turning in each idle screw until it starts to miss on that cylinder and then backing it out until it runs solidly. This will take a couple of rounds because as the whole engine starts running faster due to correct idle mixture you need to turn down the idle a bit and then reset the mixture a tad.

For the main jet you can get an idea of how you are doing by giving full throttle up a slight hill in a high gear and then lifting like 10%. If the car feels like it picks up power when you close the throttle slightly then it's too lean. This is only for the main jet though.

The idle jets are the most important and I generally start lean and see what I can get away with. You can have a pretty lean mixture at partial load and you should so the plugs stay nice and clean. You'll feel hesitation at like quarter throttle if the idle jets are too lean.

Lastly, I've seen some examples of dual carb setups having problems because the linkage isn't matched throughout the travel. You get all synched at idle but they are off at mid throttle. Try and check to see that the linkage is parallel and you hit WOT on both sides at the same time.

Posted by: Superhawk996 May 11 2023, 01:08 PM

I’d start with a fresh set of plugs - once they get carbon’ed up like that they start getting misfire. Carbon conducts electricity. Almost impossible to get them cleaned properly when running that rich on 3/4

Posted by: nditiz1 May 11 2023, 06:59 PM

2 things you need to understand for carb jetting.

1. How do you know if you are running rich or lean? Nose, ear, plug? Maybe plug, but an AFR. Unless you know what is happening while driving you are shooting in the dark regarding changing jets.

2. When does your idle jet circuit stop and your main take over? Hard to say, but you can get a feel for it by driving around with the main stack removed. You can literally drive a car up to 55+ mph only on the idles. Don't go up any large hills as you will find out fast where the transition zone is. That is when your mains would start to kick in. If you have your stacks in place and the car starts to miss and hesitate while moving through this zone you know that either you need bigger idles ( which in your case 50s will be fine) OR you need to bring the mains in sooner with either bigger mains, air corrector, emulsion tubes.

Posted by: malcolm2 May 13 2023, 06:16 PM

https://www.youtube.com/watch?v=kCXB0GVAgBA


Tomorrow i will balance with the bypass screws to get front barrels on each side to match the back barrels.

I don’t have this tune by ear down yet. So this is were i stopped.

Crazy fuel pressure gauge is still wonky. I got a new gauge to install, but it is bigger diameter than this one and has larger npt.

Posted by: nditiz1 May 13 2023, 07:54 PM

Going good. If the front to back is within a 1/2 point then the school of thought is just leave it, no need to adjust the bypass screws.

I might be on an island with my next comment, but I dont really like idling around 900 - 950. I really like 1000 - 1050. The car just seems to run smoother, but every application is different. The key is to make the engine happy. In your vid the engine seems to be running well. The drive will determine if those settings are just good at idle or under load. Also, do your same vac measurement at different RPM. So hold the engine speed at 1100 and see if both sides are the same. Do this at various points all the way up to 3000. If they are then your linkage is sync'd no need to touch it again.

One thing I did hear and maybe it was just the sound quality, but it almost seemed like a delay when you blipped the throttle for the engine to pick up. If your vac line is disconnected from the Dizzy right now then this would make sense to me. If not that then maybe I have been messing with triples too much and have forgotten the sound of duals

Mine sounds a little different, but also the end of the tuning journey
https://youtu.be/_hDlp2cK05w

Posted by: Fahren Cars May 13 2023, 09:51 PM

Jack and I are also running 40 IDFs, and we are going through the same process as the OP here. I noticed that some of the online VW tuners suggest setting float level at 10mm but the Redline rebuild kit instruction say 12mm, and then Aircooled.Net says 12mm. Can someone share insights on float levels?

Posted by: Superhawk996 May 13 2023, 10:53 PM

Already covered within this thread - page 2

Posted by: Jack Standz May 14 2023, 06:28 AM

As previously discussed, I chased a similar fuel pressure problem until I discovered a restriction (or two) in the fuel line. So maybe there's a restriction in the fuel line or tank (crud build-up), fuel filter loaded up with crud, etc.?

Posted by: malcolm2 May 14 2023, 07:23 AM

gonna get the BIG gauge on there today and see if it is more accurate. If that fails, I can pull the hoses and the filter to determine about that. I doubt CRUD is an issue as EVERYTHING is new except the gas cap.

Will drive it a bit today, maybe not too far, just around the hood and up some steep hills.

I also bought another fuel pump, I can try that if issues arise. But when the car is running and I see zero on the gauge, I can feel the pump running.

Yeah, float level measurement is a mystery still. But someone said the variation in specs comes from ethanol usage. Float sits higher I guess.

Posted by: malcolm2 May 14 2023, 07:28 AM

Here is a note about the plate and covering the small holes inside the barrel. I ended up taking one carb off yesterday, so I decided to check the plate situation.

There are 4 zig zag holes and I measured the speed screw all the way til it had fully mashed the spring.

so even at the Best Lean Idle preset, the btm hole is partially visible. Bad drawing, but here is an example.

Posted by: malcolm2 May 14 2023, 07:38 AM

A BIG THANK YOU to ALL...... great to have the knowledge that is freely given here.

Would have been hard to do it without all the ideas and examples etc...

I will update here as I put some miles on the bus....

Posted by: r_towle May 14 2023, 09:18 AM

I have a lawn mower that won’t start after sitting for probably 3-4 years.
Carb is filthy.
I went to order a rebuild kit….yet a new carb is $15.00.
Webers should be so cheap

Posted by: malcolm2 May 14 2023, 09:23 AM

Price is going up.... I bought one from China for my Weed Whacker a couple years ago. It was $14 total shipped from China. Zening post or something or other.

Yeah this rig was about $1,000 IIRC.

This group taught me a ton about the L-Jet, I should have looked for all the pieces and parts for that set up. My 914 has that, Now I got Carbs and L-Jet. So much to learn!!!

Happy Muthas day to all you Muthas!!!

Posted by: r_towle May 14 2023, 09:28 AM

You have a van that may be stored for weeks/months
To prevent you from having to remove , clean, rebuild each season I would suggest you add in a main shutoff fir the fuel.
You park it, turn off the fuel, let it idle until it dies.
You then do not leave fuel in the bowl which turns into honey, then honeycomb over the winter.
This was a standard item installed on all 356s, because carbs.

Posted by: GBX0073 May 14 2023, 11:07 AM

Appreciate all the Information. in this thread
In the process of Putting a 2056 44/38 valves Engine back together where the Shop put in big 48 Webers
I pulled the 40 MM venturi's and will try to make it work with 36MM. and a AFR
Suspect may be a loss cause ,Tempted to stop throwing money at them and getting some 40's /All of the information in this thread will come in handy when its time to fire the car back up.

Posted by: malcolm2 May 14 2023, 03:05 PM

Well, I had hoped that WE were done. I got the bypass screws set to nearly even and the idle to 1000 with everything flowing nicely.

Test Drive. Cruises nicely, up hills nicely, but I do hear a pop pop, as I come out from a stop sign and there is a bit of a hill or I am accelerating quickly from a stop.

Is that a lean POP? Maybe I didn't quite get one barrel at Best Lean Idle??

Posted by: 930cabman May 14 2023, 04:44 PM

Exactly, ditch the 48's and get ahold of some 40's with either 28 or 32mm venturi's. Will make all the difference in the world.

Also. agreed this thread has gotten some mileage from many experienced guys

Posted by: r_towle May 14 2023, 05:07 PM

You are not tuning for idle.
You are tuning to accelerate going up a hill.
Also timing, advance plates in distributor, vacuum leaks etc

Posted by: nditiz1 May 14 2023, 05:33 PM

Most likely it is a lean pop. The svda distro hooked to your vac line should be increasing the just off idle timing. As the butterfly opens a rush of air is going in effectively leaning out the mixture. The additional timing from the SVDA will help with any popping. If it pops or kicks down when you punch the gas pedal you may need to increase the accelerator pumps to account for it going lean during that rush of air.

This is where you start to data gather. You now have a running baseline. If you end up testing the accelerator pumps just be sure to adjust both the same amount and write down how much you turn them so you can turn back if needed.

Posted by: Superhawk996 May 14 2023, 06:59 PM

But it’s a lean condition that is transient. Don’t increase the idle circuit mix to go way rich and mask this transient lean condition.

As stated - the accelerator pump is what should take care of the transient.

You should be able to adjust the linkage and get there. If not, the accelerator pump bypass can be changed and so can the nozzles. Very tunable - just be patient. Pull plugs occasionally and see how they look. AFM is even better if you can swing it but remember we all tuned these back in the day without AFM.


Keep notes - don’t try to remember. Hell, I have written notes dating back to the 90s. Can’t tell you how many times I used those notes to reset carbs after rebuilds or to just remember what was done three weeks prior that I thought was helping but later decided wasn’t the fix. Notes let you go back to a known baseline easily.

Posted by: malcolm2 May 15 2023, 09:35 AM

I have been doing some searching about the Pump adjustment. I seem to be leaning toward the CC measurement as well. Gonna be tricky getting a bunch of syringes and wires etc....

Do you feel that is necessary? Even with that, the "nut turning" is required.

I counted threads and got 10 threads or so showing on each.

More threads will equal more PUMP, right?

So i figured I would turn 1/4 turn and drive. Hitting the same stop sign and load point each time until I get no popping.

Sound logical?

TO BE CLEAR.... when you say LINKAGE above, you mean the accel pump linkage, right?

Posted by: Superhawk996 May 15 2023, 09:51 AM

Yes, sorry for lack of clarity -- I meant the accelerator pump linkage. At this point, don't mess with your main carb linkages.

I never did the CC measurement thing. Can't be a bad thing. I just never found the need.

I think you'll find that you will need more like 3 (or more) turns (in) to make a meaningful difference that you'll perceive. Also be aware that adjusting the nut has a limited range of increase / decrease. It is usually enough to move the needle so that you can learn what the engine wants. However, to make bigger changes, the accel pump bypass jet (bottom of float bowl) and/or the nozzle will need to be change. Not likely you'll need to do this but if you find that moving the nut in helps but eventually it doesn't help moving it in further, you've reached the limit of what can be done via the nut.

Moving the nut is just tweaking how far the accel pump diaphram is allowed to move as it sucks fuel in.

The accel pump bypass jet varies how much fuel is allowed to flow backwards back into the bowl when the accel pump is activated. I forget how Weber sized these by number. A zero bypass does what it implies, basically a one way check valve that allows fuel in but no flow in reverse direction back to the bowl.

Posted by: malcolm2 May 16 2023, 07:54 PM

In High School, I had a buddy.... used to buy and trade Trans Ams..... He would go drive one and tell me "I'm not gonna get too excited about it...."

Well, I am pretty EXCITED about it tonight.

I moved each side's pump nut in 1 turn..... big help

then a 1/2 turn..... maybe a bit more better

+ another 1/2 turn (2 total)..... No POPS.

And I was driving with the hatch off so the engine was roaring right there with me. Remember this is a TIV 2.0 in a 72 bus.

These were short drives, from cul de sac to cul de sac not really any big hills. Enough load to make it pop before, but not now.

Tomorrow I will travel a bit further.... This is great.

Now, who is gonna tell me what adjustment or tweeking will be next??? Is there a next?

Thanks again. Longer drive is coming!!!

Posted by: rhodyguy May 16 2023, 08:11 PM

I think you got it. Button it up and drive around. I would not stray too far. Carry the appropriate tools. Have fun!

Posted by: 930cabman May 17 2023, 10:10 AM

This is a great experiment for us carb guys. I have lived with pops, sneezes, and the like for many years simply by being lazy. At least now I have one less excuse

A big shout out to all contributors

Posted by: GBX0073 May 17 2023, 12:52 PM

T oo US Carb Guys

Posted by: r_towle May 17 2023, 12:58 PM

Carbs are better than FI

Posted by: nditiz1 May 17 2023, 03:51 PM

I'm a carb guy and do not think carbs are better than MFI, EFI, CIS

Posted by: r_towle May 17 2023, 04:47 PM

1) carbs are better than FI
2) you cannot turbo a 914
3) it’s not a real Porsche

@clay what some of the other longer term “laws” regarding the 914?

Posted by: Superhawk996 May 18 2023, 06:58 AM

After driving some more - keep monitoring plugs to determine if running rich or lean.

Really suggest that you find a nice flat stretch of road where you can get up to about 60 mph for a bit. Pull the main jet / emulsion tubes. Super easy to do. Get a feel for how much time is spent driving on idle circuit and where that transition to the mains occurs. Without the mains in place, that transition will be where the car just begins to fall flat the more you open throttle and the higher the RPMs. Don’t drive in that condition for long (you’ll be running lean) but find it then back off / slow down - back to running on the idle circuit.

That transition to mains is dependent on speed, load, throttle opening, and RPMs. It really helps to get an idea of just when you need the mains.

When you’re done playing - just put the main tunes back in and you’ve now learned more about your carbs and tuning them - for free!

Posted by: malcolm2 May 21 2023, 03:41 PM

Update: added 1/2 a turn today. Total of 2-1/2 turns in now. Still getting some pops. It was said here that it might take 3 turns to make a difference.

Still the plan here? Seems to be about 12 threads showing on each.

Posted by: 930cabman May 21 2023, 05:16 PM

Is this with the accelerator pumps? If I recall correctly the spec calls for 7mm of threads showing (70 y/o memory) might want to double check

Where are your idle mixture adjustment screws?

Posted by: porschetub May 21 2023, 10:38 PM

No expert but thinking 2.5 turns is pretty much the norm then change idle jets up a small amount ,as mentioned you have a lean condition under load which isn't good for your engine,maybe try 52's,if you have rich backfire on overun bring the screws in by 1/4 turn
Try that and see how you go,I'am presuming your engine is well tuned with recent valve set and ignition spot on,cheers

Posted by: malcolm2 May 22 2023, 06:33 AM

New carbs set up by AC.net started with 10 threads of the accelerator pump arm visible on both carbs. I am up to 12 threads visible now.

That equaled about 2-1/2 turns IN.... no idea about millimeters. but would guess 1 per thread.

Mixtures screws started at 3 turns OUT from seated. I went thru the Best Lean Idle process several times and ended here.... Best guess on the screws would be 1-1/2 to 2 turns OUT, as the BLI process has you turn the screws IN.

Posted by: malcolm2 May 22 2023, 06:39 AM

Well it is 2.5 turns from where I started... not the tip of the rod.

been talking Lean backfire on here...... now you mention rich backfire.

How do I tell the difference?

I did buy 2 sets of jets.... one up from here and one down.

here is a pic of 1 side of the accell pump rod.

Posted by: rfinegan May 22 2023, 07:58 AM

Did you try to pull the main stack, and drive around on the idle jets? Conservative Throttle/driving should not need an accelerator pump.
Did you check the sync of the carbs at 1500 rpm or 3000 rpm? The last video seemed to pop/fluter on cracking the throttle? If you want to know what it sound like if the carb cable is out of sync, just crack the slave carb a bit, and it will flutter and pop, as it will not drive the master card. I have the tangerine cables and not the sync link, but the theory is the same. I seem to recall you had issues with the mounting of the cams binding? They do need to be tight and no play to the throttle shafts, (like the original arms that came on the carbs) I chased a lot of sync issues here till I got me in order...Great progress by the way
Little tweaks here and there is common. Once you find your sweet spot you can drive with out touching them for miles and miles.... and any and all the time you have spent setting these up and be reproduced in about 30 mins or so..Cheers

Posted by: nditiz1 May 22 2023, 09:24 AM

You will never know whether you are lean or rich without an AFR gauge.

When are experiencing the backfire again? Is it only at right off idle, i.e. taking off from rest?

Posted by: malcolm2 May 22 2023, 12:12 PM

The pop-pop comes in a couple places. But not consistent. taking off from rest, but usually with a higher load, say up a hill. And Shifting from 1st to 2nd. But it seems to be just those type conditions. And as things warm up, I don't hear it.

A friend does have, or DID have a AFM set up with a tail pipe sniffer. I used it on my 914 before I welded in a bung. Been bugging him to find it and loan it to me again. Not sure the cord will be long enough for the bus. Might have to set up a video to record it going down the road.

Also have been looking online to buy one.

Any thoughts on Brand?

Posted by: malcolm2 May 22 2023, 12:15 PM

Have not done that yet.... set-up wise, what is removing the jets gonna tell me. I understand that it will give me a FEEL for where the MAINS kick in, but what else can I learn there??

I did CHECK the flow on the carbs at 1800 rpm. But I only checked it, did not adjust anything at 1800rpms

Drivers side was 11 on the front barrel and 12 on the rear.
Pass side was 10 on the front and 10 on the rear.

So is it recommended to re-sync at that RPM? Kinda go back and forth from 900-ish to 1800-ish adjusting so all 4 barrels are flowing evenly at both RPMs??

Posted by: nditiz1 May 22 2023, 12:40 PM

AEM UEGO wideband is the one I use in almost every car.

If it only pops when the engine is cold, don't worry about it. Carbs are cold blooded. My carbs pop when cold too, as soon as the engine is warmed up, smooth and no pops, well some on decel, but that's to be expected, no load, burning what's left.

Posted by: r_towle May 22 2023, 12:43 PM

I’m a big believer in ensuring the carbs are perfectly balanced side to side.

I went through something like 6 different x-bar linkages until I went to cable actuated.

If one carb opens slightly slower than the other from idle to just off idle, you will get popping. It goes away once you open them both a bit more.

Because we all spend a lot of time in stop and go traffic, tuning for that off idle response, and making sure the linkage is exactly the same on both sides is paramount.

Having two different readings side to side brings me back to the linkage adjustment, and finding the flaw in the design.

Secondarily, an AF mixture in the tailpipe will be meaningless for you for this problem because that will only test a mix of all four cylinders.
It will not help you isolate why the two sides are different.

Back when Chris Foley was racing a lot he invented some cool exhaust port standoffs for his header with integrated exhaust gas temp sensors.
That is how you really tube carbs.

For your issue, I’m still wondering why the two sides do not match.
Once they do match, I suspect the popping will disappear all together.

Rich

Posted by: malcolm2 May 22 2023, 12:53 PM

OK. so my flow at idle (950) was
DS front 5.25 (needle was touching the 5, but slightly higher)
DS rear 6 (needle was smack on the #)

PS front 5.25
DS rear 5

Some folks say "close enough" some say get them dead nuts....

I will take a look at the cables today. I am pretty sure I have no extra binding, I did have that earlier in this process, but I never really looked at the timing of the pulleys.

Posted by: r_towle May 22 2023, 01:15 PM

Watch the movement of both carbs just off idle.
That is the key moment.
Slowly pull Accel cable until 1/4 to 1/2 open
Notice the difference side to side

Posted by: r_towle May 22 2023, 01:19 PM

10 on one side, 12 on the other.
That stuck in my head.

Posted by: nditiz1 May 22 2023, 04:29 PM

Oh wow I missed this, yeah you definitely need to make sure they are close at all stages of the throttle. Also, if at idle front and rear are in sync there should never be a front at 11 and back at 12. One reason why I hate crossbar linkage. At least for a bus you can look directly at the carbs instead of a top view like in a teener

Posted by: malcolm2 May 22 2023, 04:30 PM

interesting thought here.... the Drivers side is the SLAVE. So if there is slack in the cable, wouldn't the flow on the DS be lower than on the Passenger side?

Posted by: rfinegan May 22 2023, 04:55 PM

I bring this up as it seem to be a lot of talk up changing the idle jet sizes...Driving on the idle jets circuit will give a better idea if you rich or lean and can tune that first before moving to the transition circuit, main jets and accelerator pump. The AFM will be best but reading the plugs will get you there too, one step at a time.

General rule here for the mixture screws: Plates below transition holes
1/2 turn from closed or less = jet too big
1/2 to 1 1/2 from closed = jets ok
1 1/2 or more from closed = jets too small
You can have slight variations between mixture screes but they should be close each other
Jets size will be tuned when you get to the transition tuning stage. (step 5)below

Syncing the idle is EZ, as you have a throttle plate screw on each side. The final speed can be adjusted with air bleeds and timing if needed.
You can follow along as there are a few write up on this :
Example:
https://www.aircooled.net/how-to-use-a-wideband-to-tune-your-carburetors-on-the-vw-flat-4-engine/
snippet :
The carburetion adjustment is carried out as follows:

1. Adjust the position of idle throttle just below the machined progress holes in the body (using a vacuum hose).

2. Synchronize the second carburetor.

3. Adjusting the idle speed with the idle screws to a value at the bottom of the 14 / 14.7: 1 range a little richer than the stoichiometric point for good idle stability. The idle speed should be around 800 RPM.

4. Adjust the idle speed to the desired value by adjusting the idle by-pass screws, or by increasing the idling advance value, check that the maximum advance does not exceed 28 / 30 ° before TDC.

5. Idle jet selection, main nozzle assemblies / emulsion tubes / air nozzles removed. We aim for an AFR of 16/17 in order to obtain a low consumption in cruising. Re-adjust the idle speed at each idle jet change.

6. Selection of the air nozzle, main jet assemblies / emulsion tubes / return air nozzles, with oversized main nozzles. The hole between the progression circuit and the main circuit must disappear by gradually increasing the size of the air nozzle.

7. Select the size of the main jet by accelerating at full load, aiming at an AFR of between 12.5: 1 and 13: 1, ideally 12.75: 1.

8. Reassemble the pump stem nuts and screw them in until the slightest hesitation during a very sudden acceleration disappears completely.

9. ENJOY YOUR “NEW” TOY!

Posted by: malcolm2 May 22 2023, 04:59 PM

The Weber book, or some book I had, had me start the flow check using the FRONT barrels. It mentioned to use the barrels closest to the shaft controls. One reason why the FRONTs match. But I think you mis-read, I do not have a match on a CARB at idle. table below might help.

Also had replies that said, "if the flow is close, leave it..." Some said, "they never touch the bypass screws...." Some gave a range to adjust to, like the 0.25.


Anyway, It seems that after I VERIFY the cable sync is activating both carbs at the same time......

i should go back and putz with the bypass screws and

1. get all 4 equal at idle.
2. then tweak a bit at a higher rpm
3. then tweek a bit at idle again.... back and forth until both speeds have very close flow across the barrels.

Should I try even higher RPM, like 3000?

Posted by: rfinegan May 22 2023, 04:59 PM

If you have big differences in from and back on a carb make sure the plates are closing at the same time. It is very common to have twisted throttle shafts on used carbs. These are new so it should be fine?

Posted by: malcolm2 May 22 2023, 07:04 PM

WELL DAMN>>> the slave carb was a bit behind the master. The Sync-Link is very easy to adjust that.

Video shows the slave pulley turning at the same time as the cable moves. It WAS NOT doing that prior. The cable was loose.

Rest of the vid is the engine running and me reving it. I hear no "flat spot". Do you, or anything else??



https://www.youtube.com/watch?v=_4DanFqkpYc





Test DRIVE: I did hear just one POP this time. It moved. It was as I shifted 2nd to 3rd. But it only did it that one time.... FINGERS CROSSED

Since that was an issue and I have been adjusting the Accell pump and now have them adjusted IN 2.5 turns from new. Should I consider returning the nuts to where they were?

Posted by: rfinegan May 22 2023, 07:37 PM

Sounds much better...did you sync with the snail or just first movement of the slave?

Posted by: malcolm2 May 22 2023, 07:44 PM

I double checked with the snail after I tightened the cable.... All flow numbers FOR IDLE still match the table I posted above. made no changes there tonite and no testing over idle.

But I do want to know about the accell pumps I adjusted. Thoughts on returning those?

Posted by: r_towle May 22 2023, 08:21 PM

That sounds better, much better.
Go drive it

Posted by: r_towle May 22 2023, 08:28 PM

I would stop adjusting now.
I would swap in new plugs, drive it till hot, try to shut it off while revving with no idle
Then read the plugs

You are down to just reading the plugs now without a EGT sensor on each port….and don’t worry, reading plugs is how it is still done.

Google how to test and read plugs
Specifically the process.

For me, when I think I am right, I take a highway run.
I line up an exit at speed then shut it down and glide into the rest area.

Plan ahead, find a simple safe place todo this

The idle circuit is naturally very rich, so it will make the reading of the plugs false if you idle too long after the run.

Hard to explain.

But, before you adjust anything you now need data.

Posted by: porschetub May 22 2023, 10:56 PM

Not likely the throttle shafts are twisted due to them being new.still a good point as if the arm or cam wheel is not supported when tightening this will happen ,had that on one of my Zenith carbs and had to replace on spindle and the jointer coupler...so you never know.
Anyway I degress,have read this one over and over and IMO there is a vacuum problem caused by valves that aren't seating correctly or a leak @ the manifolds/carbs,reason for saying this is;
incomplete combustion as seen on the plugs ?,could be ignition issue also ?,
uneven vacuum reading well out of specs and not correcting with tuning,
uneven setting "tip in" idle on throttle stops,
valves not seating when closed ,could be correct lift not dialed or geometry wrong ?,
piston rings haven't "bedded in " so a compression test will reveal that ,
What we don't know is with other variable's but I would be a doing a compression test first,think you are over carb tuning as the vacuum is the issue here.
good luck and cheers.

Posted by: r_towle May 22 2023, 11:13 PM

Pretty sure a compression test was one of the early things that he did, maybe at the beginning.

Posted by: porschetub May 24 2023, 10:34 PM

Thanks Rich ,missed that...not good for a "fresh" build ,even with low comp pistons it should be 125 psi even ish if run in properly ? the variation between cyl's 1 and 3 exceeds what is the norm even for a used motor .
Think the OP should do another compression test when engine is warm and if result is the same put a squirt of oil down the plug holes,if a retest shows an increase thats the issue,if as I suspect you will need to do a "leak down" test on your valves also.
Don't for a minute trust the manifold gaskets with the common intake manifold kits around,the EMPI ones for example are very soft and too thick causing leaks after they are fitted ,ask me how I know,most likely better check that first.
I persist asking about this but fitted 36dlra's to my last carb case from 411,NOS raised top pistons and 1.8 barrels,fully rebuilt heads,my carbs had little done to them but setup on a bench and cleaned,motor ran unreal almost out of the box as they say,so without being a dick something is wrong here reason I'am asking,cheers.

Posted by: malcolm2 May 25 2023, 10:55 AM

Something could have gone wrong. The mechanic here is me. Even doing the BEST LEAN set-up in the beginning was challenging to me. The Weber to-do list was not clear for a real carb beginner, like me. Poorly written, if you ask me.

Part of the reason I paid AC.net for the cleaning, set-up and jetting, etc..... I figured I could follow directions to get the damn thing on the road.

This process has taught me a good bit, but not near enough yet.

It is running nicely now, or at least I would rank it as NICE. Ran some good hills etc... this week. Bus is a different animal vs the 914, wow is it different.

Gonna put some more miles on it and take the plug reading recommendation after I fix a few other items.

Thanks again everyone.... Stay tuned.

Clark

Posted by: r_towle May 25 2023, 01:43 PM

Congratulations.
remember...same (or less powered) motor...yet add in terrible aerodynamics, and about 1500 lbs.

The great thing about a bus is it teaches you how to plan when you want to pass someone, or go up a long hill.

momentum is your friend.

Rich

Posted by: majkos1 Aug 19 2023, 08:29 AM

hey guys,
Kevin here,
been lurking here ,working on a friend 914, fresh rebuild, trying to carefully break in the motor,, even added zinc for peace of mind.

I'm a Fuel injection guy, absolutely hate carbs on a stock 914 motor.
so you know where I come from.

anyhow, helping my friend here, and willing to learn about carbs and their adjustment stuff.

I had dual carbs on my Type III awhile back, so familiar with them.
(I even put back the fuel injection the ole Type III had.)
another story.

After fidgety with the 40's Weber carbs,
get them settled in,
removal of throttle linkage info was valuable !
(someone else had rebuilt motor and install the carbs)

experiencing constant backfire issues.
someone mentioned the exhaust may be leaking?
I wouldn't doubt because the improper used of washers on the exhaust studs,
I corrected em,

should I remove the exhaust to inspect for leakage or is there any other suggestions for me?

Me and Joe, his 914, are trying to get his 914 ready for Red Rocks.
will appreciate any info or leads.
Thanks!

Posted by: majkos1 Aug 19 2023, 08:30 AM

oh yeah,
his motor is a 2056

Posted by: Superhawk996 Aug 19 2023, 12:42 PM

Where is the backfire occurring? Out of the intake manifold or in the exhaust system?

No point in messing with the exhaust if it’s backfiring out of the intake

Posted by: majkos1 Aug 20 2023, 06:53 AM

yes, back firing through carbs.

Posted by: Superhawk996 Aug 20 2023, 07:00 AM

Verify plug wires vs firing order.

Verify timing

Verify valve lash - especially on intake valve but do both intake and exhaust while you’re there. This should be done before adjusting carbs if there is any question about what valve clearances are.

Posted by: technicalninja Aug 20 2023, 07:01 AM

SuperHawk has good advice:

If ignition timing is correct, advances working then.

Compression test, leak down test, R&R heads to repair poor sealing on intake valves would be my next steps.

If comp/leak down were good I'd be confused.

Posted by: majkos1 Aug 20 2023, 07:10 AM

Thank guys!!

I was wondering about the valves too,
Previous mechanic was a lil out there, and I inherit this mess.