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

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

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.

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

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.

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.

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

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.

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.

top 1/2 of PAGE ONE of http://www.redlineweber.com/html/Tech/idf_...nt_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?

Click to view attachment



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

Click to view attachment

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

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

Click to view attachment

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.

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.

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.

Click to view attachment

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

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-throttl...arburetors.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.

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!

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

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

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.

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

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.

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.

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.

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?

Click to view attachment Click to view attachment

3-4 are running really fat.

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

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

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.

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.

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

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.

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.

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
2056 dual carbs

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?

Already covered within this thread - page 2

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.?

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.

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.

Click to view attachment

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....

Click to view attachment

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

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!!!

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.

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.

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??

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

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

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.

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.