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Re: TR3 Compression

To: "George Hahn" <geohahn@azstarnet.com>, "TR" <triumphs@autox.team.net>
Subject: Re: TR3 Compression
From: TeriAnn Wakeman <twakeman@cruzers.com>
Date: Mon, 22 Mar 99 09:46:42 -0800
>
>What is typical compression (lbs) on an unmodified 1991cc TR3A engine?
>
>Any opinions on how wide a variance I should see among cylinders before
>I become concerned that there's a problem?

Compression is a funny thing to measure accuratly. Clearences are looser 
(with lower pressure readings) on a cold engine than a hot engine and 
cheap gauges are not always accurate.

Personally I do not like to burn my hands removing plugs at hot engine 
temperatures so I run my compression tests cold and look for pressure 
differences between cylinders instead of the elusive correct operating 
temperature compression. 

I'm happy if I see everything within 5 pounds of each other but don't get 
concerned until the lowest drops below 15 pounds from the highest.  I 
would then start thinking about finding a convient time to do a valve job.

One thing I like to do is run a compression test a few hundred miles 
after a valve job and record the readings for each cylinder.  Sucessive 
readings would be compaird against those readings.  There are individual 
differences in the cylinders that can make for a few pounds difference.  
So having a reference reading to compaire against helps me keep track of 
individual cylinder changes.

I would say that as long as your compession is within 15 pounds across 
all the cylinders, you have oil pressure and no noticable colour out the 
exhaust you have a drivable TR.  Mabybe a little over simplified but 
basically true.  I would be more concerned about stresses from cylinders 
with radically different compression than an overall uniform low 
compression.

Take care

TeriAnn Wakeman                              Coming soon
Santa Cruz, California                    New hub web site for
twakeman@cruzers.com             everything Rover and expedition equipment
http://www.cruzers.com/~twakeman    Links-cars for sale-special equip.
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