The car is a 1991 L98 corvette, it's stock. The engine just had new rings and all new gaskets put in it. It starts up and drives around fine, but the idle in park and neutral is at 1800-2000 RPMs. When you put it into gear it goes down to about 1200. Could it be the rings haven't seated yet? A mechanic around here told me that chromemoly rings took a long time to seat.
I just took out the IAC and it's a little dirty, so i'm going to clean it. If that doesn't solve the problem does anyone know what else I should look at? Also will a 305 IAC work for a 350? I have two 305 TPI setups here that I can use for spare parts if I need to.
Thanks.

 

do you have the throttle screw backed all the way out ??
If your old motor was a dog and you raised the idle on it to stabilize it now that you have a fresh motor that could be the culprit.

 

I had an high idle problem and it turned out to be a Throttle Position Sensor. My high idle was on a 1991 Z28 305tpi and on a 1994 Z71 5.7tbi. The TPS fixed both. Not sure if that is your problem, just something to look at.

 

Well I stuck the 305 IAC (which was clean) back in it's place and it dropped the idle to 1000 but it goes up and down a couple hundred rpms. As for the idle screw I never messed with it.

 

Vacuum leak.