The Stovebolt Site Forums The Shop Area Engine Shop Ignition advance question

This is a theoretical question, not specific to any particular vehicle, but would apply to anything with a gasoline engine and a distributor.

I think that centrifugal advance in a distributor is used to make spark plugs fire sooner as engine speed increases to make up for the fixed time it takes for the gasoline/air mixture to burn. The net result is the peak cylinder pressure aligned with the piston’s position. If I’m wrong, tell me why and this thread can be closed out.

Using specs for my ’52 GMC (same distributor is used in same year Chevy trucks.), centrifugal advance actually starts coming in just above idle, is 22 degrees at 1700 RPM and is “all in” at 32 degrees at 2600 rpm. So, if increasing the timing advance between the advance up to 2600 RPM is a good thing why isn’t continuing to advance timing above 2600 RPM not a good thing?

My question is even more obvious when you consider a more high performance engine such as a 1969 Camaro Z28 302 V8. Specs for that engine shows an “all in” of 36 degrees at 3000 RPM. Factory red line is 6000 RPM, so no additional advance for the upper half of the engine’s RPM range.

Just like to know.