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So I was tuning the MSnS and kept advancing the timing, and feeling it pull harder and harder. Never heard any detonation, and was satisfied with the 93 octane tune when I roasted "the wheel" after shifting into 4th pulling on the highway (was in straight line as well).
After several days of driving with this tune, but only occasionally stepping into the gas when in the wide open coast clear, I was cruising around with the laptop data logging as usually and noticed my coolant temp no longer at it's solid 180-182. It had gone all the up to 192, which got me worried. Sure enough, after about 5 more minutes of driving it was at 200. I start driving home, as easy as I can, 20 minutes later, pulling onto my street I'm at 216.
I get out of the car, and the reservoir is boiling.
After cooling just a little, I do a compression test, 175-175-175-175. Sweet. Next I do a CLT (cylinder leakdown test), 90 psi of shop air, shows no bubbles in the coolant, or rise in the coolant level. So I pull the thermostat out, seal it back up, and put this Lisle coolant funnel securely attached to the filler neck. Let it run and only after about 30 seconds, does it start pushing up into the funnel. I snap the throttle a couple times, and see ever so tiny bubbles come up in the funnel, blown headgasket aka lifted the head.
The 90 psi on the CLT was not enough to push through the gasket, doesn't compare to the 1000-2000 psi produced during combustion.
I try re-torqing the ARP head studs to 95 ft.lbs.
When I'm tearing the head off, underneath the car looking at the back of the block, I notice I was pushing some coolant straight out of the motor I lifted it so well. Ouch.
Put everything back together, and same problem. Should have done it right the first time...
I get a new OEM headgasket, with the new Mopar Gasket Spray they have (part number in the directions the head gasket comes with). A $20 can to replace the $20 can of copper gasket spray I've used only a few times.
I find a blow out the back of cylinder 3, and dried up coolant on the outside of the headgasket. But that's not all...
Looks like the culprit was heavy detonation. Detonation that I never saw, but my pistons sure did. You can see where it blew the carbon right off the tops of them on the intake side. There are edges of the pistons missing from being blown/burnt off.
I'm wishing I would have rigged up some piston oil sprayers when I built up the bottom end, or at least discovered those homemade "det cans" you can make to listen to the detonation posted up in the turbo forum.
I checked the block and head with a straight edge, and still .000" warpage. I could have o-ringed the head and block when I had it tore down to prevent the liftage, but then those pistons would probably have ended up in pieces.
Since my compression is solid, I'm going to try to run on these pistons with say 3-4* of timing pulled from my map when not on race gas, until they pop.
Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician
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