In my 1969 camaro I have a scb 383 with aluminum heads, pro billet distributor with the msd 6al box. I just recently took my muncie 4-speed out to try a th350 for the track. Ever since the swap, when the motor warms up (about 180 degrees) and is shut off, it will not fire back up untill the water temp. cools down to around 160 degrees, which takes about 30 minutes. The starter spins over just fine, just no fire. I thought it was an extra heat problem so I wrapped the headers, and put another trans cooler after the radiator. Someone told me the wieght difference between the flywheel and flexplate would through my timing off and not fire when hot, I haven't checked my timing or set it since the swap.
I need help bad. The car is now unreliable to drive anywere. Any help would be GREAT. thanks, Taylor.
how can the flexplate, or flywheel or whatever you're using, cause a change in ignition timing? Ignition timing is handled by the distributor which is geared off the cam. Whatever is hanging on the either end of the crankshaft will not affect ignition timing.
it's most likely heat soak in the carb causing a mixture problem,
next time it happens manually close the choke on the carb and see if it fires,
if it does then your float level is too low and/or your idle mixture is too lean.
Aside from that, when it doesn't fire when hot just to rule it out and i would check this first, pull the wire going from the ignition coil to the distributor at the distributor end, and hold it about 1/8" off somewhere on the intake or thermostat housing which is clean metal to provide a good ground, have someone crank the engine and see if you get spark. If you don't then that's the problem, or another problem. Hold the wire with a rag or glove so you don't get shocked. If you get spark then reconnect it and close the choke, if that works then it pinpoints the problem to the carb.