CYLINDER HEAD TESTER
BY MARK ELYEA
AS WE VW FLIERS know, we must remove our cylinder heads
often (perhaps too often) to lap in the valves due to compression loss. This loss is caused by stuff—rust, unburned lead
deposits—on the exhaust valve seats. We could fill the magazine debating the cause of these deposits. So, suffice it to say,
these deposits must be removed to restore compression.
The only thing worse than going through all this work is to
get the heads back on the engine and find out that you still
didn’t get the problem fixed. Yes, I’ve done that. Not wanting
to go through that process again, I dreamed up a way to check
the compression with the heads off the engine.
I built a simulated cylinder from a 3-inch PVC plastic pipe
cap (it’s actually 3-1/2 inches inside diameter). The outside
diameter must be turned down a little in a lathe to fit into the
92-mm cylinder bore in the head. A differential compression
tester is used to check the compression. I cut a rubber gasket
from an auto inner tube to provide a seal.
Reprinted with permission from the Jan-Feb-March 2004
issue of Sonerai Newsletter.
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ILLUSTRATION BY JOHN A. JOHNSON
HERE TO FIT
A RUBBER GASKET FROM AN AUTO INNER
TUBE PROVIDES A SEAL.
THE CAP AND SEAL ARE CLAMPED TO THE CYLINDER WITH A
PIECE OF ½-INCH BY 1-INCH STEEL BAR STOCK, HELD IN PLACE
WITH 3/8-INCH READY BOLTS