Dual carbs sluggish acceleration

[Theichelberger]

Hi there y'all, I've been having some troubles with my dual weber 34 ICTs. It idles pretty smooth but as soon as you accelerate it kinda stumbles and it's really slow getting up to rpm, I've set timing and synced both carbs and have the linkage adjusted pretty evenly, I'm just about out of ideas.

The engine in question is a 1200 with the Big bore kit with dual single Weber 34 ICTs and it has a 019 distributor set at 30° total advanced

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Check spark plugs , spark plug gaps,fuel filter, dirty air filters,jets, wrong jets, dirty carbs ,carb fuel level, check for vacuum leaks check the carb accelerator pumps....

[PeteSC]

I'm assuming by 1200 you're referring to a 40hp, of which I am not as familair with, but I'll offer a couple other items to consider-

-On my 36hp engine I found that the 010 performs MUCH better than the 019. The advance curve for an 019 comes on very slowly by comparison. I don't know how accurate the graph below is but there are lots out on the internet that are similar. Part of the issue may be dual carbs introducing a larger volume of fuel/air off idle than the 019 timing can keep up with.

-I'm again assuming the 40hp has similar characteristics to the 36hp, which is a pretty inefficient combustion chamber design. The dual carb 36hp engines seem to like a lot of timing. There are very reputable vintage speed engine builders who have confirmed as much on a dyno (see here and here). 30 degrees might not be enough. I can not stress this part enough though - DO NOT attempt to advance your timing without using an air/fuel meter to make sure you're not too lean. I have the timing set on my 36hp engine at 37 degrees max advance. The carbs are jetted for it, with an AFR between 11.5-12.5 at wide open throttle. I can drive it all day in the hot and humid south in peak summer, oil temps stay below 200*, and it gets almost 31 mpg on road trips...so don't be scared of adding timing, provided the engine is properly jetted for it.

[l3illN]

Are you running a fuel pressure regulator? I run a set of 34's and found them to be very susceptible to over fueling if the pressure is above about 3psi. VW fuel pumps can put out 3X this number.

[heimlich]

Did you try messing with the advance (turning the distributor) to see if the curve needs to be looked at?

The 019 doesn't need to be at 30 all in. You have some wiggle room. Many 019's only advance 16 degrees total and might not be enough for you.

Where in the RPM range are you having issues?
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[Theichelberger]

I'm truthfully have issues at all rpm ranges, but most of all probably around 2,800-3,000 rpm it's got absolutely no power, the over fueling is definitely something I forgot to consider, the engine used to run like an absolute beast with the current set up, snappy throttle and plenty of power, the old fuel pump went and I replaced it with another one.

[heimlich]

I would go through and do a tuneup and check everything such as valves, cap, rotor, condenser, wires, and spark plugs. Make sure the timing is set correctly. Check the advance at 1,000, 2,000, and 2500 RPM.
_________________
www.vwnos.com [email protected]
Classic Brands. Classic Quality.
Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
5% Off your order with coupon code: 5%OFF
Restored Distributors Available (<--Click here)

[wagen19]

[JonnyB32]

Hi I'm looking at doing the same mods as you ,do you think it's your carbs read this article on setting up weber ict carbs on www.wayoutwestie.com he show the jet sizes needed and fuel regulator etc ! Hope this helps?

[Theichelberger]