ezstriper

the blue crank says it all, lubrication failed first...

NautiSouth

While it's hard to dispute that the hydrodynamic film broke down, I think it's a jump to say that the cause is the lubrication system. This failure could very well have been caused by overpressurization of the chamber (due to detonation or otherwise) leading to extrusion of the bearing material or fatigue and spalling of the same. If the bearings are compromised, the presence of lubrication oil is no longer sufficient to keep the asperities separated, which can lead to heat-bluing as we see here.

So, the hydrodynamic film failed... but what was the root cause? How do the other bearings look (as asked before)?

abones

I agree with Nauti.. Crank jounal for #1&2 7&8 seem to be ok (from what I can see), So It seems the Oiling system was still working, I'm not a professioal engine builder but if I was to guess, the oil film was compromised by detonation or rod bolt stretch/failure/fatique Just what I can see from the pictures the brg material does not appear to be paper thin, and the big end of the rods in pic #4 are not dark blue. I don't know?

ezstriper

look at the rod laying in the pan, blue as well, as far as other bearings, not going to tell much as metal was flowing everywhere at that point, if was a rod bolt failure( and have had those) does not blue up parts, just cuts loose quickly, and if it detonated so bad as to kill the oil, the tops of the pistons would be killed, only damage I see is from the pistons hitting the head from the bearings being spun and continued to run, this thing had to have been struggling for a while before just gave up...

payuppsucker

I'm with Nauti and abones, like from the beginning. The mains will tell the tale but I'll bet detonation killed this motor.

payuppsucker

I didn't hear a thing when I did almost this exact same thing to one of my motors two years ago. I noticed a little loss in speed, looked down and saw OP falling, chopped the throttles and turned to look behind me, saw a big ball of blue smoke. Too much timing, not enough gas, boat had been running out west at high altitude and was tuned for such. Worked good for 5500' ASL, not so well for 250"ASL

1BIGJIM

iTrader: (1)

I thought I would post a couple of pic's of a piston that was removed because of Detonation and a broken ring landing. Both engines ran fine, perfect oil pressure but had a lot of blow by. Notice scratching on the skirts of the pistons when they rock back and forth. Even if the piston kissed the head they will still have scratch marks in the bores and side of pistons.. I ran these engines lean, mis calculation on my primary jetting. These engines had over 100 hours on them. Brand new 502's....

fleg1

bingo!!!!

Baja Rooster

iTrader: (1)

Auto engines are typically built with tighter tolerances that can hold high RPMs for a short time, but not so much on long extended runs at the rev limiter.

Baja226sport

iTrader: (28)

Block adapter and oil cooler were removed during tear down. I just spun a filter on to keep it from dripping on the driveway while taking the rest apart.