Chugging, surging, and bucking. Whats wrong with my Webers/Porsche?

[EarlyPorsche]

My 66 is running like crap. I think the carburators are the culprit. Its bucking and surging and shaking. At half to full throttle its just like it was, but down low its running terrible. I did fiddle with a mixture screw and the idle speed screws. I think I may have made the engine run uneven. What do I do to fix this situation?

[Joe Bob]

Fiddle before or after it ran like crap?

When did you last change the fuel filter?

[EarlyPorsche]

I can't remember why I fiddled with it, but I suspect it was because it was idleing low and a little poping at lower RPMS out of one venturi. Fuel filter is fresh. I have likt 5 or 6psi of fuel it seems like. I just took out all 6 adjustment screws and turned them out 2.5 turns yet it still surges getting up the RPM ladder. I just bought some NGK B6ES plugs. I hope those work with my Electromotive crank fire. I have a fan on the engine now, when she cools off I am pulling the plugs. Hopefully I have a fouled one.

[Mo_Gearhead]

Early, use the search function ... lots of threads on Weber carb. adjustment. However, without an Air Flow Meter you will have a struggle adjusting them correctly.

[EarlyPorsche]

Well I know its either bad spark plugs or a dirty set of carburators which I am leaning toward. The engines internals are all healthy(no noises or indications of problems there, clean oil, and so forth). I have a fan on the engine right now, I will let it get cold then I will install the new plugs and test drive her. If she still surges then we know that the real problem is the carburators. At which point I think I will pull them and clean them up real good.

[viejopatron]

Have you looked at the ignition? I've got same symptoms on my Weber-fed 2,2 and suspect my very old Marelli distributor advance mechanism.

[EarlyPorsche]

Yeah my ignition is a electromotive crank fire, I have no distributor. The ignition is fine, I can't see how that would cause this. The plugs may be bad, even though they are very new I may have been running a bad mixture on them. Now I have all the screws turned 2.5 turns out. The tip of the mixture adjustment screws was all black and disgusting when I pulled them out. I suspect my Webers need to be cleaned up.

[carsngolf]

I agree your Webers probably need some attention but the number one culprit in my book would be the idle jets. They clog easily and they're the first thing to investigate. In case you're not familiar, they are the topmost fittings on the fender side of the carbs. They use a flat screwdriver and have an "O" ring which seals against the outside of the body. Unscrew the holders, pull the jets out and see if you can see clearly through them. If not, clean them with carburetor cleaner and compressed air. Reinstall them and hopefully you'll be amazed at the difference. If that doesn't work, the next item is to pull the main jets. They're the hex bolt brass fittings at the bottom of the float bowls. Those jets unscrew from the hex fittings. Clean them the same way. It's unlikely they're clogged as the hole size is much larger than the idle jets but it's an easy job. If you still have stumbling at light throttle application, the next suspect is the accelerator pump. You should be seeing squirts of fuel from the pump nozzles as soon as you open the throttle. If not, stumbling is inevitable.

[carsngolf]

Just reread the initial post and realize now you were talking about Solex carbs. I know nothing of Solex types but suspect they are quite similar to Webers. My advice was based on longtime personal experience with Webers so it may or may not apply.