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Old 01-06-2012, 08:53 AM
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Originally Posted by yragat
Its a 1960 390 ci Cadillac----Want to know what total timing (with vac disconnected) should be and at what RPM it should all be in by

I know a sbc is usually good at around 38 degrees all in by 2500 rpm
But don't know what the Caddy likes
Most gas powered auto engines will perform best in the 32-38 degree total mechanical timing range with the vacuum advanced disconnected and plugged. The 'all-in' should also be in the 2500-3000 RPM range for street driven vehicles.

The idea is to use the highest degree of advance timing that you can without getting any detonation. This will yield the best overall performance. Keeping the 'all-in' RPM in the 2500-3000 range will also help the performance because you will normally be close to that RPM when cruising and should be in the peak horsepower and torque band for your engine.

A simple test to check for pinging is to drive at a steady speed (around 35 MPH) in high gear up a slight incline (a freeway overpass will work). If any pinging occurs, lower the timing 2 degrees and re-test. If no pinging occurs, increase the timing 2 degrees and re-test. What you are looking for is the timing set at the highest degrees with no pinging.

Some will suggest going to the dragstrip and adjusting the timing to yield the highest MPH going thru the final set of lights. This is great for a drag vehicle, but not so much for a normally street driven vehicle. You do not normally drive on the street at max RPM (which is closer to what you would be attempting on the strip).
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