Timing Adjustment to Fix Overheating Problems
Short answer: To rule out timing as an overheating cause: disconnect and plug the vacuum advance (its only purpose is gas mileage), then set the initial timing to 8–14° BTDC and see if it cools.
How the advance stacks up: initial timing (~8–12°) is what you set at idle; mechanical advance adds ~20–25° as RPM rises for ~32–38° total; and vacuum advance adds more at cruise (up to ~55–60° on a ported source, which has no vacuum at idle).
The trap: if the vacuum advance is hooked to a manifold source, it adds ~15° at idle. So if you set “12°” with manifold vacuum connected, your real initial is about 3° after TDC — far too retarded, which overheats. (Note: most first-gen Firebirds used a temperature-activated switch that changed the vacuum-advance source to help keep the engine cool at long idle.)
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Content last modified: June 13, 2026 at 10:06 am
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