Okay. I inherited a 91 Firebird project from a friend. The car originally had a TBI 305 w/TH700-R4. As the 305 was tired, I told him he should just put in a new 350. The end result was a 350 short-block from a local machine shop (which may be 85 or earlier eng.), with heads off of an early 90's truck bought off e-bay and cleaned up, with a mild RV cam (.420/.443, 204/214 @.050), the stock TBI w/1 inch spacer, original computer, exh. etc. When I got the car from him, it wouldn't idle at all, and wouldn't rev at all, it would just barely stay running if you held the throttle wide open. I would like to interject here, I didn't have time to help him with this, so someone else did. I figured out that the pushrods were incorrect (1/2 in. too short), and after replacing them, and setting lash, the car runs and is driveable. Unfortunately, there is a vibration from idle to about 2000 RPM's. Realizing that there were plenty of simple mistakes made (one engine mount bolt just threaded into the nut, plug left where coolant temp sensor goes, 1 trans. cooler line loose, converter cover left off, etc.etc.), I'm hoping someone could suggest some possibilities for smoothing this beast out. Any help ya'll can give would be greatly appreciated. Thanks.

 

Welcome aboard.

Start with the simple and obvious. Check that the spark plug wires are in the proper order going to the proper cylinder (two adjacent cylinders in the firing order being reversed has an interesting effect). If that is okay, check for cracked distributor cap or rotor, burnt plug wires, vacuum leaks (especially on a vacuum tap that goes to an intake runner rather than from the throttle body).

 

The distributor cap may actually be the problem. They seem to have broken off one of the screws that holds the cap down, so I'll replace that. Thanks, I probably wouldn't have thought of that myself.