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Re: [Fot] LEAK DOWN TESTING CRANKCASE PRESSURES

To: Joe Alexander <n197tr4@cs.com>, 'Friends of Triumph' Triumph
Subject: Re: [Fot] LEAK DOWN TESTING CRANKCASE PRESSURES
From: Scott Janzen <sjanzen@me.com>
Date: Thu, 23 Jun 2011 12:08:52 -0400
when I did this recently, i discovered I had to remove the rocker assembly to 
get good readings, as the air pressure pushed the pistons to BDC and at that 
point, one of the valves was always either starting to open or still closing 
with the cam I have. Did not seem to be a safe way to hold the crank at TDC 
where a closed valve reading would have been possible with the valve train 
installed.
Assume you figured this out, but just to check the obvious . . . 

I had had the engine overheat and a head gasket fail when I lost an alternator 
pulley and was not watching my gauges (this car never overheated before . . . 
).  I had the head milled slightly to get rid of warp, but the machinist and I 
thought the valves and seats looked pretty good and just lapped them in.  Turns 
out this was not enough and leak-down results were still crappy because the 
heat had distorted the valves and seats.  Took the head apart again, recut the 
valve seats and valve faces, put it back together, incredible results with a 
worst cylinder 4% leak-down, and that's with no ring or cylinder work.

Good luck!

Scott 
GT6

On Jun 23, 2011, at 11:36 AM, n197tr4@cs.com wrote:

FOT








This seems like it may be a good topic.

I was getting an undue amount of crankcase pressure at Topeka.(Just now trying
to find the time to sort out)

At idle there are absolutely no engine oil leaks.  At 60-100mph the oil is
being pushed out in huge amounts. at every possible location.

This occurs in spite of otherwise very effective vacuum system we have used
with great success on the TR4 #197

Have never done a leak down test in all of these years or had one done. No
experience at all.

Results:  100/85   100/80   100/60   100/60

Pretty dismal readings if I did it correctly.

Head is off and new rings to be installed.

The benefit of FOT experience and knowledge would be greatly appreciated.

Thanks!

JOE A.
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