I csan only relate some things done on opposed 4 cylinder and 6 cylinder
aircraft engines, as this is what I have worked on most - but their
resemblances to the van engines - both air and water - are uncanny.

On the aircraft engines - we always ran the engine to get it to
operating temperature. THEN, a differential compression test was run.
Same as a leak down test. The engine was turned so the cylinder was at
TDC on the compression stroke, and with a regulated air supply, and a
dual gage regulator - compressed air was pumped in to the cylinder. Once
loaded, the gage regulator was closed, and the cylinder gage was watched
for several minutes and compared to the regulated pressure gage. The
cylinder pressure would nearly always be lower slightly or a lot,
depending on wear - than the regulated pressure.This gave a really good
comparison. This was done on each cylinder. You want to do this on the
engine while at or near the operating temperature - because all the fits
and clearances will be at optimum at those temperatures. This is where
your engine runs, so it needs to be tested where it runs.

Checking end play is also important and checking crank wobble is also
important. This is a bit more problematical, because there is a pulley
mounted on one end, and the transmission blocks access on the other. But
typical check of crank wobble is usually done with a dial indicator.

At the minimum, you should definitely get that leak-down test , and do
it at operating temps.

Regards,

John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com

Stephen Cebula wrote:
> I'm looking at an 84 Westy on Saturday.  The guy want $6500 for it.  It looks really clean but has 170K on the original motor.  He sent me a copy of the compression test he had done in 2007 when he bought it.  It shows 140psi on all 4 cylinders.  I'm planning on having another one done when I go look at it.  What would be an acceptable number?  I've heard 145-190.
>
> Thanks,
> Steve
>
>
>
>
>
>