Another reason for doing the leak down test at TDC is that at BDC both
valves will be slightly open unless the valve train is disabled.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of MilosKitchen
Sent: Thursday, January 27, 2005 6:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Leak Down Test at TDC instead of BDC

 For years, both with aircraft and with automotive engines, the leak
down
(or differential compression test) has been performed with the piston at
Top
Dead Center. The primary reason is that the top of the cylinder is where
the
most heat and loss of lube (hence the most wear) is. See the following
link.

Some (very few) engines valve overlap design might even prevent a
reliable
BDC check, but I can see how it would be easy for a one man show.

Dave

Shortcut to: http://www.w-p-c.com/buggyleakdown.htm

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