Thread: Overheating Mystery

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At the risk of helping and not offending, if I’m bothering anyone I’ll leave again.

Please check your total timing, 10° initial timing may still be wrong.
I’ll tell why, initial timing is rpm sensitive, meaning the mechanical advance can and will effect initial timing depending on idle speed. While most distributors do not engage mechanical advance below 1000rpm, I have seen some that start at 800rpm and slightly lower. If idle speed is higher than 800rpm, your mechanical advance may have started its curve, if you set initial timing to 10° you may actually only have 28° - 30° total timing and robbing your motor of a lot of power while producing too much heat in the motor (especially at idle).

Total timing is easy to set; you will need an adjustable timing light or a standard timing light and a roll of timing tape that matches your harmonic balancer (SBC is usually a 6.75” O.D. or 8” O.D.).

STANDARD TIMING LIGHT METHOD, install the appropriate timing tape, disconnect your vacuum advance and plug the vacuum line going to the carb. Have a buddy sit in the car and bring the motor rpm up to 3500rpm and hold it, using your timing light adjust the timing to read 34° - 36° on the timing tape. Now have your buddy bring the rpm up to 4200rpm and check, adjust if needed. This is your TOTAL TIMING. Let your motor idle and adjust idle speed as need.

ADJUSTABLE TIMING LIGHT METHOD, disconnect your vacuum advance and plug the vacuum line going to the carb. Adjust your timing light to read 34° - 36°, have a buddy sit in the car and bring the motor rpm up to 3500rpm and hold it, adjust your timing to zero at the timing tab on the motor (the timing light has adjusted to the correct timing). Now have your buddy bring the rpm up to 4200rpm and check, adjust if needed. This is your TOTAL TIMING. Let your motor idle and adjust idle speed as need.

Your initial timing will now be whatever it is, usually 12° - 14° (below 800rpm idle). Initial timing is not critical, TOTAL timing is. Now drive your car hard, listen for any pinging, rattling, knocking type noise while accelerating. If you hear any noises described above, lower total timing 2° and test again, adjust as needed to eliminate detonation.