Engines Come, Pistons Goe, But Those Da** Steel Shim Headgaskets Just Don't Blow!!

[boostmaster]

Well it's been a couple of weeks now since I took the 85 T on a high speed blast down a old back road. Had my girl with me and the car was pullin like a mother. Even though my boost setting was moderately low, 18psi on an 18* chip with xylene, on occasion my o2 volts had dipping dangerously low. I had run as much as 21psi before on pump gas and xylene with as little as 3-5* of KR. On my OTC scan tool for a split second I saw the o2 volts dip way low around .720mv and a huge spike in kr about 10-13kr head a little knock and backed off. Now many of you that have pit crew wives know that women are much more perceptive than men. And mine swore she heard something more sinister. Well got back to the house and noticed smoke coming out of the breather. Took a compression test and found all the cylinders except one had between 142-147psi. All except cylinder #5 wich was 107. Ah hah!! I thought blown head gasket. But i took it a step further and ran a leakdown test on bank 1-3-5 and I had 60% leakage in cylinder #1, 12% in #3 and whoa 100% in #5. Okay this could be good or bad, both cylinders w/ excessive blow bye into the crankcase. So I ordered a set off steel shim headgaskets and broke down the drivers side head. Low and behold no blown head gasket but on cylinder #5 about half way down there's a 1/8" dent almost into the water jacket. Well those steel shim headgasket sure are tough!!!, too tough!!!

 

[Intercooler]

A dent? Is that a good or a bad thing? How did it get dented? I have still shims and hate them.

 

[REDS HOT AIR]

be warned that they can leak and not be blown

buttttttttt

they shouldnt leak at the pressure level of doing a leak down test but they are known to leak under higher boost levels unless block and heads are perfectly flat and studs are lets just say really tight

 

[boostmaster]

After further inspection I think that maybe the piston ring land may have exploded. That is the only thing that I can think of that will cause such a huge crater in my cylinder bore. The top of the piston looks fine except for the heavy coating of oil that has been leaking past the gap in the cylinder. The funny thing is this dent is not sctratched up or jagged but very smooth to the touch. Kinda looks like someone took a small ball peen hammer and smacked it. I would think that if the damage was from the piston rings that scratches or other damage would be visible. Either way I'm still looking at sleeving the block and a rebuild in the long term, but luckally I have another engine to install for the moment. Man, it's always something, last year I ran a best of 13.3xx @104mph w/ 2.xx 60's on street tires. I bought me some Nittos, added alky and was really hoping to see this HOT AIR move this year. Guess I'll be taking it easy for a while.