We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re answering questions about timing for small block Chevy engines.
W.H . • Temple, TX
Q: Which way do you turn the distributor on a small block Chevy to advance the timing? We’re having a family debate—I say one way, and my boys say the opposite! Also, I believe advancing the timing on a carbureted engine (without a choke) will help it start easier on cold mornings. The boys disagree saying the spark should be retarded. And, if the engine backfires through the carb under acceleration (only when cold), is the timing excessively advanced or retarded? Finally, I think you should be able to install a distributor 180 degrees out of sync, and my sons don’t believe the engine will start, let alone run this way. How would you even know if it was installed 180 degrees out of sync?
A: Chevy distributors rotate clockwise, so you’d want to turn the distributor counterclockwise to advance the timing. Advancing timing to aid in cold starting will only help if the timing was retarded to begin with. Retarding the timing can help the starter turn a hot engine but that’s about it, so excessive timing one way or the other is not the answer.
Generally, advanced timing (up to the point of detonation) will make the engine run cooler. A vacuum advance that’s connected to the manifold vacuum rather than the ported vacuum can also reduce the engine’s operating temperature at idle. Not utilizing the vacuum advance can make an engine run excessively hot at any throttle position other than wide open.
When a cold engine backfires through the carburetor, it’s most likely an indication that your air/fuel mixture is too lean, not excessive timing.
If the the distributor is installed 180 degrees out of sync, the spark will occur during the exhaust stroke, so the engine won’t start, plus it’ll backfire out of the exhaust and possibly out of the carburetor as the intake valves open. If the rotor points to the #1 cylinder post, and the cam-gear alignment mark is at 6 o’clock, the distributor is 180 degrees out of sync with the crank. When the distributor is properly installed, the cam-gear alignment mark will be at 12 o’clock when the rotor points at the #1 cylinder post (you can use any of the eight posts for #1—the distributor won’t know the difference.)