I have some Solex H40 carbs on my 2.0. I can tell that I'm lean right off idle because of popping and so forth. I would like to jet a little richer but I can tell these damn K&Ns just let in way too much air. I covered the K&Ns with some shop paper towels and ran it around the block for a test. Man, this car actually impressed me with it's zippy response and speed. It ran much better with more air filtering.
So my question is anyone use a precharger or prefilter to smooth out carburation? I would actually love to go to a paper filter if I can find one, but these H40's are hard to find info and parts. Or, is there another air intake option for dual carbs? Remember the H40s are a single throat carb.

For running purposes, an air filter can't "let in too much air." If your car is running better with paper towels clogging the air filter, you have a carb issue that needs to be addressed.

I ran 125cc GP bikes that had no filter. You have almost no midrange without a proper air box. So you drive those things full throttle. Driving a street car is almost always low to midrange. I believe these K&Ns let in way too much air. I can jet richer but it runs good right now with a "paper" added filter. You can see light through these K&N filters. Very poor if you ask me but nowadays it's hard to find paper filters.

What he said. The whole concept is preposterous. Time to look into the jetting. The Cap'n

914-8 and the Cap'n are most certainly correct. (And they know it)

You need to re-jet your carbs.

Apparently you are running lean without the shop towels.

The reason it runs better with the shop towels is that now the engine is seeing LESS AIR and the same amount of fuel as before the towel trickery.
The engine now "Sees" a more correct air / fuel mixture.
That is what is telling us your engine is running LEAN and needs to be re-jetted.

Ya see... We have all been here before.

The above diagnosis assumes your timing is correct. Your valves are set correctly, if you have points the dwell is spot on. AND your Carb linkage is set up properly.
Plus the correct fuel pressure, your carb floats are set right.
You have NO intake leaks...!!!!!

After ALL of this is deemed correct.

THEN you re-jet the carbs to make your engine run correctly.

Think of it as a combination of things. If ANY of the above are not setup properly. You will forever be tuning AROUND the flaw. And achieving a tune of mediocrity. (At best) And that is if you are lucky...!!!!!

If you simply want to learn more about your carbs and tuning.

You might want to contact either of the following:

Mike Harney
He is truly one of the great Carb gurus in the air cooled arena.

Contact Name: Mark Harney

Telephone
Shop: 615-371-4228
Cell: 615-587-1000

Shipping Address
Harney's Carburetor Clinic
9426 Highwood Hill Rd
Brentwood, TN 37027


Or Contact Art Thraen at ACE. He is another amazing fella that re-builds and jets out carbs as very few can. He is so good, peeps send him carbs for VW and TYPE IV engines from all over the world.

Art Thraen
360 W. 6100 So.
SLC, UT. 84107
Mon-Sat 9-6
Phone: 801-747-3340
Fax: 801-747-3341
Website: http://www.aircooledengineering.com


Hope some of the above makes sense. if not.. PM me fpr a phone number and I will walk ya through the basics and WHY you should do what we are suggesting.

Cheers,
Clayton