There are up and down agreements on this. (I say up and down because I'm
getting ready to duck when people start shooting me down on this
procedure.)
A warm compression check is most accurate ........... but NEVER REMOVE
spark plugs from a hot Aluminum Head.
So before you do a hot compression check, add thread anti seize to the
plug threads, run the engine till it gets hot and then you can safely
remove the spark plugs from a hot engine. The engine needs to be at full
operating temp and it is a PITA working with it at full temp.
Otherwise do it the country boy method and do it on a cold / moderately
warm engine by just squirting a good shot of any weight motor oil into
the cylinder and giving the engine a good spinning with the starter
before you start your compression check. In either case the anti seize is
a good idea since it helps seal the threads and you don't have to force
the threaded end of the compression gauge to get a good seal.
(There are pros and cons of Anti Seize on spark plug threads, a good
squirt of Berryman B12 Carb cleaner will remove the anti seize from the
threads after you've done your testing if you want to get rid of it.)

Stan Wilder

On Mon, 12 May 2003 11:09:24 -0700 Malcolm Stebbins
<mwstebbins@YAHOO.COM> writes:
> Should I have the engine warm or cold when I check the
> compression??
>
> My van seems to NOT be firing on the right (passenger)
> bank of cylinders very well.  I've changed spark plugs
> and wires, the distributor is new as is the cap and
> rotor and still it stumbles.  It could be carburetion
> (I have a carb) or it could be a compression problem.
> Malcolm
>
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