HEI Upgrade
Short answer: Installing an HEI won’t reduce knock except by coincidence — it’s the advance curve that matters (an HEI only helps if it happens to have less centrifugal advance or a stiffer vacuum-advance spring). If knock is your only complaint, fix the advance on your current distributor instead.
With the dwell and initial timing set to spec and the engine warm, use a dial-back timing light: raise RPM until the timing stops advancing, then dial the light back to line up the mark — that’s your total mechanical advance (should be ~30–36°). If that’s OK, disconnect and plug the vacuum advance and test-drive (both full-throttle and light-throttle/high-load); if the ping is gone, focus on the vacuum advance: swap for a unit with less advance or a stiffer spring, fit an adjustable aftermarket unit, or modify yours. The advance amount (10, 15, or 20°) is usually stamped on the unit.
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Content last modified: June 13, 2026 at 10:06 am
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