Looking for advise here. I have duel 40mm Italian webers on a new rebuilt. The carbs are in synch but when cold they will spit and pop some. It does very little spitting when warm. Is this the nature of the beast or what do I need to look for next. The carbs aren't brand new but in fantasic shape, very clean through out. Also, they have to throttle milked on cold start up for a minute but then go to normal idle. They are on a 1.8 that was mildly upgraded with pistons/cylinders and cam. I don't have much info besides that. Other than that, I'm very happy with it. By the way I'm running a faucet fuel pump, I know, I need to get a rotory pump...
I know many have converted to carbs so I'm looking for advise on this.
thanks for your replies.
Chris

That's the nature of the beast. Without a choke, when cold, they run rough. Can you get a little more detailed on the "spitting." When warm they should run smooth.

Did you adjust the valves? That did help some with the cold spitting and popping on mine when i had the 2056 ...
Andy

NC has good weather, not to cold. Mine, in the morning, goes to idle pretty quick. Mine spit and sputtered until I put in the CB performance upgrade kits (click here) .

I don't know for sure if it is the 'Bullseye' design that caused it, but I suspected it. And when I saw a kit that eliminated them I went for it. And if I can keep my foot out of it, my fuel economy goes way up.

I am hopeing that Jake will become interested in testing these kits. There is alot of IDF 40's still in use.

Here is a pic of the kit installed:

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Wow, does the kit come with instructions and was it difficult to do? I'll have to look into that. thanks

Yes it came with instructions, and it was easy to do. The only tough part I remember was the "O" ring's on eather side of the spray bars. Please remove your carbs to your workbench to install these kits. Small parts like to fall into Webers.

I will look into this and post in the future.
Thanks alot
If anyone else has something to add, I'll all ears and eyeballs.

When cold, the fuel doesn't atomize as well. Thats where FI has it's benefits. Injectors do a great job atomizing the fuel.

Carbs, especially dual webers do run like crap when cold.
The 356 had an additional hot air system that blew hot air at the carbs (user controlled) to aid in heating them up faster.

Old carbed cars had a hot air hose going into the air filter...it would shut off when warm.
Its the nature of carbs.

Given that the accel pump uses its own squirters, I cant see what that CB kit is doing aside from changing the airflow characteristics that the weber engineers designed in the first place.
The original bullzeye is shaped like a wing in profile.
What does the tube do different?

Rich

Perfectly normal carb operation.

As for the CB Performance upgrade kits... goole came up with all kinds of stuff. http://www.thesamba.com/vw/forum/album_pag...p?pic_id=249791

I got these from Mike Allen years ago... (click on the image to get the full size view)



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The pic below shows bullseye over the carb with spraybar installed, the spray tube is a tiny bit smaller than the bullseye. The BE shoots fuel down one side and dumps it into the middle like a garden hose. Where the spray tube is preasurized and along the bottom are small holes that atomize the fuel into an even spray. It also comes with larger venturies designed to work with this delivery system. A little more air flow and a better atomization method. I am happy

Click to view attachment

I respectfully disagree that the popping/spitting is normal. yes, you will have to feather the throttle a bit when it is cold - dont force them to clean themselves out until the car has been running for a minute. However, the popping and spitting means the carbs are *not* in synch. Pull the linkage, get the carbs syched up and adjusted, then put the linkage back on - making sure nothing binds or is causing one carb to open. If the car runs great prior to installing the linkage, you know where the trouble is. Make sure you have the good linkage as well.

Cool Gint on the info. I got my kits about 5-6 years ago but I had not been driving it for 4.5-5 years for any distance, until until just last December. You didn't say what you thought of them? Pray tell.

Here's my carb tuning proceedure from a March 03 post:

Assumptions: the carbs have the optimum jet and venturi package (good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

Remember that the mixture and air bypass adjustment screws are precision needle valves, not head gaskets. Use your fingers to tighten them, not your fist.
Start and warm up the engine.
Make sure the two drop links for the throttle linkage are exactly the same length, and disconnected. You can use a 8mm thin igntion wrench to snap them off.
Turn the mixture screws all the way in and then 5 half turns out.
Turn the air bypass screws all the way in.
Turn the idle speed screws out til it just touches, and then in 5 half turns.
Put on your hearing protection and start the car.
Use your STE and find the barrel that pulls the most. We'll call this one baseline.
Balance the barrel in the other carb that pulls the most with the idle speed screw. (if you have a Uni-syn, give it to someone you don't like and purchase a STE airflow meter)
Go back to the other carb, with the baseline barrel. You will have one all the way in, then use the air bypass screws and balance the other two barrels.
Go to the other carb and do the same thing.
Snug the jamb nuts on the air bypass screws.
All six barrels should pull the same amount of air at this point, if not repeat air adjustment proceedure.
Snap the throttle linkage drop links back on the carbs. If the idle changes then you need to barely adjust the linkage mounts so snapping the drop links on, doesn't change the side to side idle balance.
Use the hand throttle or a vice grip and rag to lock the linkage between 1400 and 1800 rpm.
Start back at the baseline barrel and adjust the mixture screw in or out, to get the smoothest running and highest idle, then turn it in 1/4 turn.
Do the same with the five other mixture screws.
If you have to turn the mixture screws more than two turns either way, you've got the wrong jets.
Recheck side to side and individual air balance, adjust as needed.
Road test the car.
If you get snapping and poping out the intake, it's generally a lean condition.
If you get heavy exhaust fumes, or pboofing out the exhaust it's probably too rich.
If you get a flat spot or popping out the intake at between 2800 and 3200 rpm, you probably need larger idle jets.

That's a rough, five minute draft of my carb tuning proceedure, hope it helps!

If it goes good it should take about 45 minutes, if not about three years.

I posted this for a guy working on a 6, but the tuning principles are the same.

PK

Thanks everyone, I will digest all this and get some help this weekend.
Chris

I'm not actually running a set. I'd like to try it one of these days. Having said that, I've been considering sending my current set of carbs off to Art Thraen to have them rebuilt and possibly reworked a little bit. Still kicking that around... To be honest, I'd love to hear from someone like Art or Jake on this CB update kit.

To Scott's point about this not being normal carb operation, I do agree that the popping and spitting isn't necessarily normal when cold. But in my experience unless a pair of weber's are matched extremely well and the linkages setup perfectly, some spitting and a lot of throttle feathering when cold is a requirement for carbs on a Type IV.

You Guys live where it actually gets cold, a blib maybe two and I am at idle.

Are there different sized venturis available with this kit or is it just one size?

Rich

I don't know but they are pretty big already. I am sure you could take them to a machinist and have the ID cut a bit.