[Fot] Odd compression?

[Scott Janzen]

Hi, Ed
Sounds to me like you have a warped head, non-level block and/or studs that are stretched to the point where they've lost their elasticity (my engineering materials courses are 35 years in the rearview mirror, sorry if the terminology is wrong).  Too long is not an issue unless you are running out of thread to tighten the nuts.
Anyway, I'd suggest getting some new studs from ARP or another good supplier, and getting the both the head and block checked by a good machinist to make sure they're both flat, and getting the valves and valve seats re-cut.
Leakage along the outside of the pushrod galleys is not unusual - I usually assemble with a bit of black permatex over there, but not between the combustion chamber and the pushrod galleys.
Length of pushrods, etc - sometimes you can have these shortened, depending on the design.  Basically, you need to install and see if, when the camshaft travels through the lift cycle, the rocker travel across the tip of the valve is pretty close to centered.  If it's off, you'll get too much side load on the valve and wear issues.  There are lots of aftermarket pushrod mfrs who can supply new ones to the right length, or your machinist may be able to shorten the ones you have.

On Aug 23, 2012, at 5:21 PM, Edward Dunn wrote:

Did a leak down test on the GT6 motor. Retorqued the head to 75 lb ft.
Performed test, and cylinders 1-5 were leaking through their exhaust valves.
All cylinders were also leaking through the head gasket, but ONLY on the left
side (opposite intake/exhaust ports).  Pulled the head, and the intake/exhaust
(right) side of the gasket looked fine, but the left side had oil and water on
the gasket, both top & bottom of gasket.

So, it's got leaky exhaust valves, and head gasket leak. Possibly the head
studs are too long, since the head has been machined who knows how many times?
Perhaps the studs are stretched? Also, one pushrod is a touch shorter than the
rest.  I think this can be adjusted for, but it would make the geometry a bit
off, correct?  The pushrods are also a slightly different design than on my
spare engine.  With the head milled a bit, still use the original length
pushrods?

This is all puzzling to me and my non-professional but competent mechanic
pal.

Ed Dunn
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