[DeTomaso] Compression ratio question

Doug Braun doug at silicondesigns.com
Mon Sep 24 11:15:10 EDT 2007


A better way to disable the ignition during a compression test is to
disconnect the points wire or the 12V feed wire from the coil on a standard
ignition system or disconnect the magnetic or optical trigger wire(s) on an
electronic ignition system.  If you remove the coil's center high tension
wire to disable the ignition system but still allow the coil to be fired, it
may be damaged by arcing over inside.

Doug Braun
blue 73L #5505

-----Original Message-----
From: detomaso-bounces at realbig.com
[mailto:detomaso-bounces at realbig.com]On Behalf Of JDeRyke at aol.com
Sent: Saturday, September 22, 2007 10:04 PM
To: dagny-kr at online.no; detomaso at realbig.com
Subject: Re: [DeTomaso] Compression ratio question


In a message dated 9/22/07 12:15:31 PM, dagny-kr at online.no writes:

> One thing i know for sure ,is that its very important to have the throttle
> wide open when measuring the compression pressure,as you otherwise build
up
> vacum on the intake side and get wrong result :)
>
Agreed. FWIW, I block the throttles wide open, pull the coil high tension
wire from the coil and disconnect all the spark plugs, and rotate the engine
4
times per cylinder to ensure getting a full compression stroke under mnimum
load. This practice seems to result in consistent readings from one engine
to
another. Cheers- J DeRyke







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