[Fot] LEAK DOWN TESTING CRANKCASE PRESSURES

[Scott Janzen]

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 at 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.
_______________________________________________
fot at autox.team.net

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe: http://autox.team.net/mailman/options/fot/sjanzen@me.com