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Author Topic: Valve clearance adjustment with warm engine?  (Read 2560 times)

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Offline Skonnie Boy

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Valve clearance adjustment with warm engine?
« on: June 30, 2009, 02:21:41 PM »
Long story short, can I do a valve clearance adjustment while the engine is still warm?  Clymer says to perform the adjustment on a cold engine, but is this for reasons of not burning yourself, or because the adjustments will be incorrect otherwise?


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Offline TwoTired

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Re: Valve clearance adjustment with warm engine?
« Reply #1 on: June 30, 2009, 02:24:34 PM »
Metal expands when heated and changes the clearances.
Set them cold.
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Offline FunJimmy

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Re: Valve clearance adjustment with warm engine?
« Reply #2 on: June 30, 2009, 02:25:47 PM »
Heat causes expansion.
Clearances will change.
Set them cold as per your manual.
Not getting burnt is an added benefit.  ;D

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Offline Skonnie Boy

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Re: Valve clearance adjustment with warm engine?
« Reply #3 on: June 30, 2009, 02:42:06 PM »
Curses, drat, bah.

Many thanks for replying whilst engine is still warm.
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Offline MCRider

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Re: Valve clearance adjustment with warm engine?
« Reply #4 on: June 30, 2009, 02:52:42 PM »
Just to be contentious, if operating temps are 220+, and scalding is about 112, human pain threshhold about 108, so a comfortable warm temp would be about 85, and that's pretty darn close to room temp. I mean, what's "cold" in a garage on a warm summer day-85?

So how much expansion could there be from 75 to 85?   ;D

Just take a break and let it cool down.
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Offline Skonnie Boy

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Re: Valve clearance adjustment with warm engine?
« Reply #5 on: June 30, 2009, 03:44:03 PM »
Thank god I moved back to Chicago.  In three years in Austin, TX, I don't think I ever experienced "room temperature" between march and november.
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Offline TwoTired

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Re: Valve clearance adjustment with warm engine?
« Reply #6 on: June 30, 2009, 04:34:58 PM »
Just to let you know the risks...
As the valves heat they expand, which effectively reduces the valve clearance to a smaller dimension than when the valves are cold.  If you use the cold clearance dimension to set hot valves, the expansion will never reduce the dimension.  Valve clatter and the risk of "hammering" the valve stem and the tappet adjuster.  While I like mushrooms, I don't want these parts to look like them.

Set them in the morning after a good nights cool off, if you want a quiet valve train during run operations.
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Offline Skonnie Boy

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Re: Valve clearance adjustment with warm engine?
« Reply #7 on: June 30, 2009, 05:21:40 PM »
Dear lord, I want quiet valve operation more than anything else in the world right now.  I'd like to think a proper adjustment will solve my persistent misfire, but I doubt it.  This is one of the last easy things to do before I discover the joy of engine removal and partial tear down.
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