My carb...

[Freddiesbuick]

I don't have a huge big block Pontiac or Buick with loppy cam. But what I do have is more for street with some 'umf' and a V6 carbed turbo, (Buick). Made my own carb, (Frankenstein-chestor) from a Pontiac and various other carbs and an '82 throttle plate. I opened up some idle bypass thinking it won't hurt. As I was running old school grease monkey tests, (cupped hands over air-horn testing for a vacuum leak), it splashed my hands with fuel. I thought that was weird. I do have a vacuum leak in it, (I think it's in the hot-idle compensator). But I don't think the by-pass idle mod would cause that would it?

As expected cupping my hands over it increased the idle quite high and uncupping causes it to struggle back up to an temp acceptable curb idle. It's the fuel splash that gets me.

[Shark Racer]

Are the air-horn and main body a matched pair?

Plugged pump holes could cause this as well.

[Freddiesbuick]

Yeah the airhorn and main body are one. As far as plugged pump openings...I blasted that carb with compressed air to the extreme of clean.

[Shark Racer]

Was the splash coming from the air horn or just in front of it?

[Freddiesbuick]

From within the airhorn, right out the boosters.   

[Shark Racer]

Could be retarded timing coupled with a significantly lean condition.

[Freddiesbuick]

Lean condition perhaps, but the timing is at stock which is 15@BTDC.

[Shark Racer]

Are you sure the balancer/timing chain are OK? Otherwise, 15* should be fine.

[Cliff Ruggles]

Is your "parts" carb using a Buick turbo main casting and baseplate?.....Cliff

[Freddiesbuick]

Those things are rare and I didn't want to spend the ridiculous money on the few left. So I modified the base plate I had of an 82 Buick Electronic carb. It's easy. I wish I could upload pics to show what I did. But there are no issues with the engine or timing since I'm just experimenting by backdating it. As it was before I began fiddling around with this hybrid carb I modded it runs beautifully, (it's a CCC system so it used the ECM controlled carb and HEI).

I backdated it to a vac controlled HEI and a non-CCC carb I got off of an 80 Pontiac. The APT now draws manifold vac not from the plenum but directly from the manifold. A three way check valve protects the APT from boost, (during boost the vac is drawn from the plenum). 

[Cliff Ruggles]

I've modded and used CCC carbs for high performance use, even set a few up to run straight off the jets and they worked flawlessly.

The baseplates are easy to modify to supply vacuum to the PP if needed.  The turbo carbs typically routed the vacuum in externally so they could install a valve to keep from pressurizing the bowl under boost. 

The internal check valve is a much better deal, IMHO.....Cliff