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Just read a 1978 service manual that said to adjust valves hot, not cold
Found this old Chilton's guide for a Chevy 350 in my grandpa's garage. It clearly says to set the lash with the engine at operating temp, which is the opposite of everything I've done for years. Has anyone actually tried this on an older pushrod motor?
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simon7176mo ago
Wait, you're saying the manual specifically says hot? That's wild. I've always done them cold on my old small blocks because the metal expands so much. Maybe they figured the hot clearance is the one that actually matters when you're driving.
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stellap936mo ago
Yeah @simon717, hot is the spec for a reason. The cold clearance is just a guess, you want it right when the engine's actually running.
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olivia_allen6mo ago
Actually the metal expansion is why you set them hot lol. The clearances close up when everything gets warm, so if you set them cold you're basically guessing at the right gap. That old manual is correct, you want the lash right when the engine is at its normal running temp.
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