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.

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.

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.

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.

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.

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.

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

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

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.

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...

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.

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?

Click to view attachment

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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.

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.

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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.

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.

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

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

PM sent.

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.

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

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.

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

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??

Jegs QFT 793-30-804 (the one I purchased)

Keep us in the loop as you get her purring.

Synced ?

I’m hoping you nail it!

Rich

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.

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

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?

How does she run? WOT? seems to idle ok

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

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.

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

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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

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??

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.
Click to view attachment

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
Click to view attachment

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

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.a...de=897346002931

Yes, +1.

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

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. .

NGK BPR6ES

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.

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.



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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?

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.

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

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/639...=1&CartID=1

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

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