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Valve clearances DECREASE when engine cold?
Quite a regular
Quite a regular

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Maybe I'm just not the sharpest tool in the shed, but I always believed that as the engine gets hot , valve clearances will decrease.

I just set the valves on my 32 902 to 0.004 with the engine good and hot after a long run. This morning before putting the valve cover back and the engine stone cold thought I'd see what the clearances were when cold. The intakes had essentially zero clearance and the exhausts were only 0.001 or 0.002. So all clearances got smaller as the engine cooled.

Is that supposed to happen? If so then why don't we set vdlves when the engine is cold? I'm now inclined to set valves to 0.004. when cold.

What do you think?


Posted on: 2017/9/11 11:55
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Re: Valve clearances DECREASE when engine cold?
Home away from home
Home away from home

Troy Taylor
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Yes, they will....

Having rebuild 5 of the pre-war engines 28-32, The valve clearance gets wider when the engine is hot. Everything in the engine expands with heat, so as the engine heats up the distance from the cam to the rockers increases.

The factory spec should be considered the minimum and there is no good reason to ever set them tighter, you could easily damage the engine.

Intake .0025 Cold and .004 Hot, Exhaust .004 Cold, .006 Hot.

It is important to insure your HOT adjustments are correct, a little time consuming, sometimes a pain in the butt, but important non the less.

Posted on: 2017/9/11 14:39
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