Guys,
I have changed intake gaskets on my car recently and it has the best idle I can ask for since I started driving it. The question I have is why do I have a high idle after a short wide open throttle run? If I go through all of second gear and let off, it takes a while for it to settle down. Is this the ported/ manifold vacuum switch on the intake causing the timing to be held high? What else could cause this?

Carb has been completely gone through and has no binding. The throttle shafts have been drilled and bronze guides installed for good consistent sealing. The distributor is a new unit and the mechanical advance is not sticking. I cannot say if the vacuum advance is sticking as I have not checked.

Any guesses?

 

Here is a guess from me....possibly float level too high in carb or too much fuel pressure if ya have an electric fuel pump.....I would say that its not a vacuum advance problem. Are you sure your throttle return spring is stiff enough??....I would lean heavily on a fuel problem....just too much gas or throttle plates not closing on the carb.....just my 2 cents....

 

Are you completely sure the carb throttle plates are closing correctly? I've had a similar situation and the problem ended up being the gasket between the float bowl and the throttle body on the Qjet. The gasket was just a little ragged in the throttle openings and the throttle plates would sometimes hang up slightly. Be particularly careful in checking the secondaries. Assuming this is a Qjet, be sure the link that forces the secondaries closed is adjusted properly.

 

Sounds kinda like the fast idle screw is not set right, or sticking.

 

Yeah I had the carb stick on my old 307 motor. It's amazing how loud a car can be a 3500 RPM's with stock exhaust.

It stuck another time, but just like I learned in driving school, I floored it and it was fine after that, didn't stick again in the remaining 4 months that motor lived

 

I actually hadn't thought about that gasket but the base plate gasket could be causing drag also.

This is a Q-jet. The throttle plates move very easily when off the car and seat very nicely. Again the bores for the throttle shafts have been bronzed so I feel confident this is not a vacuum leak at the throttle shafts.

The return spring is healthy enough but has the placement at the carb linkage moved from the factory return placement. I like it to pull directly from the same spot as the pedal so the force vestor is equaled out.

I have checked the primary side when this condition happens to make sure it is returning to the set screw but I didn't pay attention to the secondaries. I will check that.

The fuel pump is the factory style mechanical and the float has been set and checked twice with a new float so I'm pretty confident in this setting.

The car does run slightly rich at idle all the time but I thought that was because of the cam choice.

I have a 67 Chevy truck and I just realized it doesn't do what the Cutlass does so I started asking. Let me get through these suggestions and I will get back with probably more questions.

 

My two cents, check to make sure the return spring you moved isn't catching on anything. Just a thought.