lower compression when hot???

[BTGUSA]

This is a strange occurance for me. Does anyone have any experience with this? The engine has been assembled as many before it have. here are the details

2000cc
I4
tubocharged GT3076R (the real one)
15psi boost.

engine has run for 350 miles
cyls 1-3-4 have ~140psi evenly
cyl 2 is running 84psi when cold and has only 30psi when warm

this was veryified by 2 technicians and 4 different guages.
there is a deffinite leak past the rings when leak tested on cyl 2.

the cylinder walls were coated with anti friction coating and i am hoping this is just causing the rings not to seat properly.

strangely engine does not appear to have a balace problem while running.

any advice with 84 cold and 30 hot would be nice. i am going to try a few more psi boost to see what happens.

after that it will come apart for inspection anyway.

 

[patprimmer]

A valve is not seating properly. maybe a tappet is to tight, especially on the exhaust or maybe a valve is sticking in the guide or is very slightly bent.

Regards

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[malbeare]

BTGUSA,
try squirting some oil into the cylinder and retest
if the compression does not rise then you have a valve problem if it does rise then it is the rings


A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

http://www.sixstroke.com

 

[CrdStang]

I once had a Nissan VG30 that had compression on all cylinders while cranking, but one dropped to near zero while running. Being a bit dumbfounded, I changed the offending bank's cylinder head and fixed the problem. Now I suspect a lifter had a clogged bleed orfice and was thus pumping up and holding a valve open. Just something to consider..