I dyno engines for a few shops, and ran a pontiac for one of them on Tuesday that destroyed some bearings. I would like to get some opinions on what caused this...as I am very curious myself.
The engine is a 400 pontiac block, with an EAGLE stroker crank, not sure on the stroke, CID ended up around 450. Eagle H beam rods, and an SRP piston. bearing clearance from their records was .0024 rods, .0028 mains, a Clevite H series rod bearing (BBC size) and P series half groove mains. The crank is cross drilled out of the box.
Engine fired up right away on the dyno, oil pressure was 60 PSI. Has a hyd roller cam, so after 25 minutes of running oil (rotella 15-40) was dumped and the filter inspected. Filter looked like a bit more than average for debris, but not enought that red flags needed to be raised.
Started making some power pulls, 3200-5500, watching the usual stuff. Timing was set at 32, the a/f ratio was 12.3, and the plugs looked fine. This dyno has full exhaust, so you can hear the engine quite well, no noises from the engine during any pull... BUT.... Oil pressure was going from 60-55 during this sweep. That was strange, but not a show stopper. It was not like what you see when the oil is too full in the sump (this is a stock pan, with some sort of windage tray). Oil temps were fine, maybe gaining 3 degrees during each pull, temp measured in a modified oil pan drain plug I use.
Made 3 pulls, power was repeating nice, 580 tq, 520hp. Then after a check for leaks, the next couple of pulls, the engine lost 20 ft/lbs across the board, but the oil pressure and the oil temp did not show a change.
I rechecked timing, and also the Wide band sensors, they were both unchanged. Could hear a bit of noise from the engine when giving it a quick rev, so the filter was removed and there was a ton of bearing material.... end of dyno story.
I had to go into the city yesterday, so I stopped by their shop. It was all apart, and some tremendous damage had occured.
Main bearings 4 and 5 were worn some, but 3 was really bad, 2 was bad, and 1 was just starting to get into copper.
Rod bearings, 1 and 2 were not too bad, but 3 thru 8 were absolutely pounded.
I took some pics and they are here:
After seeing the damage, I was amazed that the engine was not hammering really bad. The oil pressure from the first pull to the last was within 3 psi.
Any ideas from the minds here is appreciated,