Twin Turbo LS1

[Blown353]

Jason,

If the bearings are smoked but you managed to get 12K miles out of it my guess would be very, very light and probably intermittent detonation and not continuous sky-high cylinder pressures.

It takes a LOT of force to push the hydrodynamic oil wedge between the bearings and reciprocating parts out of the way and get metal to metal contact; about the only thing that will do it is sudden and severe shockloading... and that would be detonation.

My guess is the thing pinged so lightly you couldn't hear it, it was below the resolution of the knock sensors (if you're still using them), or it was transitional knock that only occurs very briefly under specific loading conditions but it was just enough that over 12K miles it hurt the bearings.

How do the plugs look? Any little itty bitty tiny black specks on them? That's a sign of very light detonation-- not enough to pull metal or deform the ground strap but just enough to rattle the rings so they lose seal and release tiny droplets of oil that then get baked onto the porcelain.

Sucks for sure any way you slice it, but I'll take damaged bearings over hurt or ejected "hard parts" any day!

The thicker head gaskets, while lowering the compression ratio, increase the quench distance and can actually increase the chances of detonation.

Another possibility that I dealt with in a Mustang 5.0 with a Kenne Bell blower: it would hurt head gaskets from time to time and the plugs showed very light pinging no matter how much timing the guy pulled out of it or how much fuel he added at steady state WOT. I dinked with it a while and found that there wasn't enough acceleration enrichment which is VERY critical on an instant-torque (i.e instant cylinder pressure) roots type blower. It would just lightly rattle every time you stabbed the throttle to the floor hard. After a couple months of that it would push the headgaskets. I increased the acceleration enrichment and no more problems.

Jason, if you're going to go back through the motor I would do a +.005 overbore and torque plate hone it. The factory doesn't torque plate hone them. You can pick up some ring seal. Also, if you change the head bolts for studs the rehone should be a requirement anyways as changing fasteners can actually have an impact on the clamped bore distortion. Better safe than sorry!