Need some help - My son and I have a 68 Chevelle that actually overheated to the point that it stalled. Ever since when we put the vehicle into gear @ idle it runs awful to the point it almost dies. It still idles great in park and runs excellent on the road. We have done the following:
Changed vacumn hoses, spark plugs, spark plug wires, distributor cap & rotor, fuel pump and even the timing chain (which was sloppy). None of this helped so we've even rebuilt the stock Quadrajet. Again to no avail. Performed a compression check and nothing radically wrong. Does anyone have any ideas? The car is a stock 327/275HP w/ 2 spd powerglide. I'm starting to pull my graying hair out so any help would be greatly appreciated. Thanks.

is the idle set high enough so that it does not drop too low when put in gear?

Danny

We've adjusted the idle rate to the point where if it's any higher the car is slammin into gear when shifting out of park.

what kind of choke is on it? (If there is one)Does this only happen when the car is warm, or at startup. you may have to toy with the mixture screws. It should idle at about 1000RPM in park, and about 650-700 in park is what my 327/th350 likes.

The choke is the stock coil spring mounted in the manifold - and believe it or not it still works. The performance problem shows up hot or cold. I've been playing with the mixture screws since rebuilding the Q-jet and no luck there either. The only non-stock item on the motor is the distributor. It's an HEI unit - I've never had problems with these and would not know if it could cause a symptom like this?

Did you double check the timing with a light? I had a 327 a while back that did the same thing. It was a timing problem.

Sorry I did not respond to tips sooner fellas, I don't get much of a chance during the week to work on the problems. Did find out a couple things today.
1) Can not set the timing with a light. I'm getting a reading of about 7 degrees advanced with the light and can not come close to the recommended 4 degrees BTD. This was the same problem I ran into before changing the timing chain and gears. The only non-stock item on this 68 is an HEI ignition...would that cause this?
2) In going around the engine with carb cleaner to see if I could find a vacumn leak I found that the engine speeds up when I shoot the cleaner in the left front primary. It slows down when I spray the right, which is to be expected. Played with the fuel mixture screws and could not stop this from happening - any thoughts on this? I really appreciate the time and input I've received. It's almost impossible to find anyone that knows musclecars,everything is rice fed nowadays. Thanks, and please keep the input coming.

I assume this is an automatic transmission. Since the car overheated have you had any other problems (i.e. trans shifting ect.) perhaps the transmission fluid was overheated to a point that damaged the torque converter causing problems when it is put in drive?

I would first check the timimg though and set it correctly when it is in gear (have son put in drive and hold brake!!) if it is ok or acceptable check trans fluid for burnt appearance or smell.

Just a thought

Joe

Thanks Joe, I'll give it a shot and get back to you.

HEI requires a full 13 volts. The standard 68 has a resistance wire that lowers the voltage to 8-10volts. Drives the HEI nuts. Ours ran confusingly if that is a word. Specially at idle.

Also check the voltage. Regulators can go and drive the HEI mad again.

We paid to rebuild a carb etc., etc., new carb, only to discover the new regulator was defective.

I'm not sure about the overheating but, this is a real long shot. Make sure the key in the crankshaft has not sheared or the balancer broken. You said you couldn't set the timeing correctly. I've seen the balancer slip and throw off the timing mark.