[Bmcu] TR3 compression test

[Ron Christensen]

Hi Jeremiah,

You may be getting a compression ratio that will not be happy with today's
low octane fuels. Since you did not cc the head you would only be guessing
at the new compression ratio.  I usually see about 160 psi on a race motor
with about 11:1 compression ratio. My current Sprite has about 10:1 and I
have a problem trying to run straight premium from the pump.  I go to the
airport and pick up 5 gallons of LL100 ($5 a gallon) which I mix 50% with
premium no-led from the gas station and it works just fine.  (an added
benefit is the fact that I am introducing a little lead to the fuel which is
good for the valves and guides)  I also purchase race gas (leaded 110
octane) ($8 a gallon) and do the same mixture.  I have not had much success
with the so called "octane booster" additives. 

If you hear any pinging or the dreaded death rattle you may be burning
pistons.  Check the plugs for signs of aluminum. A light dusting (white in
color) on the electrodes is actually your pistons finding a new home on that
set of champions you just installed. The best way to get an accurate plug
check is to do what is called a "clean shut off" which is accomplished by
turning off the engine after a few minutes on the highway and pulling over
and checking the plugs without doing any idling.  By the way, don't do this
if you have a "modern" car with locking ignition.  A friend of mine, the
late Miles Roberts did this at a race once in a "borrowed" 280Z (SSA car)
and added a 4" diameter steel pipe hood ornament as he was entering the
pits.  Headlight alignment was a serious problem after this modification
also.  The car's owner wasn't too pleased.

Ron Christensen 



-----Original Message-----
From: bmcu-bounces at autox.team.net [mailto:bmcu-bounces at autox.team.net] On
Behalf Of Jeremiah Curry
Sent: Tuesday, March 18, 2008 8:54 PM
To: bmcu at autox.team.net; triumphs at autox.team.net
Subject: Re: [Bmcu] TR3 compression test

Thanks for everyone who responded to my e-mail below.  I ended up buying a
new gear reduction starter and when testing with the starter, the
compresssion rate definitely went up.  Now I am worried it may be too high.
Here are the results front to back:
140 psi
130 psi
155 psi
145 psi

I think since the head was shaved by the previous owner and then I had it
rebuilt, I have a much smaller compression chamber.  Is this too much over
the expected 120 psi that I should be worried?  Or is the 25 psi differnce
worrisome?

Thanks,
Jeremiah

-----Original Message-----
From: vtr-bounces+jercurry=comcast.net at autox.team.net
[mailto:vtr-bounces+jercurry=comcast.net at autox.team.net] On Behalf Of
Jeremiah Curry
Sent: Tuesday, January 22, 2008 11:35 PM
To: vtr at autox.team.net
Subject: [VTR] TR3 compression test


howdy all,

I just put the head back on my TR3 the other day and wanted to make sure I
did everything right, and that the parts were all good.  We did a leak down
test and 2 of the cylinders where "yellow" and two were "green".  To be
doubly sure, I borrowed a compression tester from autozone and did that
test.  My starter has decided not to cooperate since then, so I had to turn
the engine over with the hand-crank.  Due the manual nature, I only went
through about 2-3 compression cycles, but the PSI rating for the cylenders
were from 30-60 psi.  I understand I should be looking for 120 psi.  Is this
an indication that something is horribly wrong?

to test the tester, we put it on my brother's 5.2L jeep v8 and it got 85
psi, that seemed a little low too.  Any insight would be appreciated.

thanks,
Jeremiah

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