That is the same setup use to check compression on aircraft piston
engines.
>-----Original Message-----
>From: Robert Allen [SMTP:boballen@sky.net]
>Sent: Saturday, April 26, 1997 4:57 PM
>To: MG List
>Subject: Tech Session - Leak Down Tests
>
>Attended a tech session today at a local garage where I got to watch a
>pretty neat demo of a leak down tester. The host (Craig Vaughan, Foreign
>Car Enterprise) was trying to show us the importance of good diagnostics
>and good compression.
>
>He was using a dual face gauge attached to an air supply. With dual
>faces you can see how much air is going in and how much air is going
>out. When you get 50 pounds going in and 40 pounds going out you have a
>leakage of 20% -- that is a number you can work with to improve. The
>'average' car can be expected to have leakdown in the 10 to 12% range. A
>good valve job and high-tech rings can bring leakdown to the 2 to 3%
>range. That is almost a 10% compression improvement all by itself. (He
>is a distributor for Total Seal piston rings by the way.)
>
>Back to the tech session: He had a '67 Jag roadster in the shop and
>suspected some compression problems. On one hole, he put 50 pounds of
>pressure at TDC through the spark plug hole and was only holding 40.
>There was a noise. Taking the radiator cap off we could see and hear air
>bubbling up. No brainer! Head gasket. On the adjacent cylinder, he
>repeated the test. There was more noise. Coming though carbs. Cracked
>valve.
>
>This was done after a compression check that identified those two holes
>as suspect. I thought that was a pretty neat diagnostic method. Two
>gauges and he was pretty sure where the problem was (compression test)
>and what the problem was (lead down test). Cool.
>
>I just may need to get one of those leak-down gauges to complement my
>compression teseter. Summit has one in their catalog that is a Tavia,
>has the part number TAV-08015 and is priced at $63.69. Their compression
>tester is part# SUM-900009 for $21.99 (older catalog not listing their
>toll free number 330-630-3030. of try their web site at
>http://www.summitracing.com).
>
>Bob Allen, Kansas City, '69CGT, '75TR6
|