<VV> compression test

[burkhard at rochester.rr.com]

Matt's right about it being best to run the test warm, but Andy riases 
a legiimate point about taking plugs out of a hot engine.  I recommend 
this:
1.  With the engine cold, break all the plugs loose, but don't 
really "loosen" them.  They should only move a fraction of a turn.
2.  STart the engine and let it wamr up to normal head operating 
temperature... This might take quite a while at idle.  I'd give it at 
least 20-30 minutes if you donot have a head temperature sensor on the 
engine.
3.  Stop the engine and remove the plugs and follow the rest of ANdy's 
procedure.  Because you broke the plugs free when the engine is cold, 
they will come out very easily (no extra abuse on the heads' threads) 
when warm.   Don't forget to keep the throttle wide open and make sure 
you crank long enough to get a good reading.  I also keep the battery 
on charge throughout this to avoid 'battery droop' and slower cranking 
by the time you get to the last cylinder.

I would not get hung up on the actual numbers achieved.  Ideally, the 
difference among cylinders should be less than 10%, but I would not 
pull an engine apart until it was a LOT worse than that ... over 20% 
difference.

Have fun!

Jim Burkhard



----- Original Message -----
From: TimogensTurbo at aol.com
Date: Tuesday, April 17, 2007 9:52 pm
Subject: Re: <VV> compression test
To: virtualvairs at corvair.org

> In a message dated 4/17/2007 6:31:24 PM Pacific Daylight Time, 
> johngull at bellsouth.net writes:
> 
> > I need help in knowing when best time to take compression test 
> is: motor
> > cold or motor warm? As well as what PSI rating should I be 
> looking for? 
> ===================================================
> 
> Always Warm / Hot!   WOT / Choke fully ope / all 6 plugs out !
> Depending on your engine build, it has be 40 yrs...so who knows!  gg
> 
> minimum 120 psi......no more than 5 psi difference between 
> highest and 
> lowest.....
> 
> 
> 
> Matt Nall...west coast
> http://members.aol.com/patiomatt
> lots of info!
> 
> 
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