#2, #4, #6, and #8 pistons (driver's side) are broken on a fairly freshly built Cadillac 500. Like 700 miles and 8 hours.
Other side of the motor looks like brand new. Like only 3% leakdown with cold cylinders.
It pretty much always had blowby (enough where the PCV valve couldn't keep up since day 1) but I was told it was because the rings hadn't seated but seemed strange to me. 10-15% leakdown depending on cylinder (#4 and #6 the worst). First motor I paid someone else to assemble and I regret it now. Anyway, I kept running it. Blowby never got better. It was also better when the engine was cold than warm.
Crazy part is that it still ran fine right up to when it started pushing all the oil out the front of the motor due to so much blowby. Limped it 200 miles home pissing out a quart of engine oil every 15 miles didn't help the bearings any but it still held 40psi at idle but basically only stopped when the lifters didn't keep the valves open. Leakdown when I got it home was 80%.
I did have spark knock for a brief period (Davis Unified Ignition/DUI sent me a garbage distributor with 40 degrees of advance that went to 16 degrees of advance at idle and 40 by 3100rpm). Never seen all the pistons on only *one* side of the motor go from detonation. There is no pitting in the crows or any cracks. Most of them aren't even broken between the two compression rings. It is always on the front of the piston below the oil control rings.
Dual plane intake so if it was running lean on one side (TBI motor) it should have taken out two pistons on each side of the motor.
Ideas?
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