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By 55blacktie - 7 Months Ago
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Howard's Cams recommends a valve lash of 0.022; I'm assuming that's hot lash. Of course, the initial lash before start-up will be set cold. If you search the internet, you'll find as many opinions regarding whether cold lash should be greater or less than hot lash, and that doesn't include variables such as aluminum heads on iron block, etc. If the recommended hot lash is 0.022, what should the cold lash be? I hope there's a consensus; we're not talking about motor oil. Thanks.
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By stuey - 7 Months Ago
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Hi
http://forums.y-blocksforever.com/Topic68227.aspx?Keywords=valve%20lash%20aluminium%20heads
May be of interest.
That was a while ago, did not realise I've been at it that long.
stuey
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By Ted - 7 Months Ago
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For cold solid lifter valve lash settings on an iron head/iron block combination, I’ll set the valves ~0.001” more than spec. For aluminum heads on a cold engine, I’ll set the valves ~0.005”-0.006” tighter than spec. These numbers are good for the initial startup and run-in but setting the valves to specification once the engine is at running temperature is always recommended.
Aluminum heads on an aluminum block with a solid roller or flat tappet camshaft can see a minimum of 0.020”-0.025” expansion at the valves from cold to hot so those can be tricky. These require almost a zero valve lash cold to avoid excessive valve lash when hot. Hydraulic roller or hydraulic flat tappet camshafts on aluminum headed aluminum block combinations solves many of the valve lash variation issues on those particular engines when preloading the lifters 0.030” or more.
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By DANIEL TINDER - 7 Months Ago
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No differentiation between intake & exhaust cold iron/iron settings?
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By Ted - 7 Months Ago
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For first start or cold start, I’ll not be concerned about any differences in the intake versus exhaust valve lash settings unless so specified by the camshaft manufacturer. In theory, you would set the exhaust valves 0.001”-0.002” looser than the intake valves to compensate for additional exhaust stem expansion. When you reset the valves under hot conditions, this would be compensated for automatically as that difference in expansion would already be present.
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