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Overheard a guy at the parts counter about valve lash and it hit me
I was picking up brake pads at Napa on Tuesday and this older guy was telling the clerk about his 1968 Mustang running rough at idle. Clerk said check the valve lash cold, not hot. I never even thought about that. I've been adjusting mine after a 20 minute warmup for years. Went home, measured at cold, all four exhaust valves were way too tight. Fired it up after and the ticking dropped right off. Anyone else been doing it hot this whole time and getting away with it?
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perez.christopher3d ago
Read a tech bulletin years ago that said most old Ford small blocks had the valve specs written for cold settings from the factory, but everyone assumed hot because that's how the old guys did it. The exhaust valves on those 302s shrink as they heat up, so setting them hot leaves them too tight once everything cools down. Your cold gap should have a little extra room, like .022 on the exhaust for a stock cam, and that's where the ticking usually goes away. I switched to cold on my own 289 and the difference at idle was night and day, smoother and no more clatter.
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