died on the dyno. your veiws please

[LJ851]

1) incorrect assembly
2) debris in oil /passageways
3) lack of sufficient oil pressure for whatever reason

[LJ851]

You obviously haven't been around too many engines. Rod bearings fail, pistons start stroking 1 or 2 mm more than normal, piston hits head, compresses ring land, and massive blowby/leakdown occurs.

Damn, i'm good.

[Mercury[BKM]]

Damn, i'm good.

toot toot! good call lol

time for the re-rebuild =(

[tg318is]

Wow! That sucks mate!

[AndrewBird]

You obviously haven't been around too many engines. Rod bearings fail, pistons start stroking 1 or 2 mm more than normal, piston hits head, compresses ring land, and massive blowby/leakdown occurs.

I suppose so. I wouldn't think 1-2mm would make the piston hit the head, but 5-6mm like the OP has would. lol That is a VERY spun bearing. Frankly I'm a little surprised it would still run and/or didn't break something internally.

[nando]

1-2mm will definitely lead to head/piston contact. An engine designed with a good quench area (like an M20B25) doesn't leave a lot of room between the piston crown and combustion chamber. 5-6mm? that's like a 1960s inline-4 with flattop pistons..

[329jay]

1) incorrect assembly
2) debris in oil /passageways
3) lack of sufficient oil pressure for whatever reason

i built it. i plastigauged the shells and the one that went was the tightest one but still within spec.

all oil ways were de greesed and blown out.

new bmw pump.

[urbancynic]

I've had brand new oil pumps fail on me before. Luckily I caught it immediately, but still....

That sucks man.

[delatlanta1281]

i built it. i plastigauged the shells and the one that went was the tightest one but still within spec.

all oil ways were de greesed and blown out.

new bmw pump.

Dumb question, but you did use assembly lube on all bearings and parts that are touched by other moving parts? That'
s gotta be bad part/ assembly/ starvation. what do the valves look like in that cylinder? If it was a timing problem, there would have to be another piston with damage no?

[10Toes]

1-2mm will definitely lead to head/piston contact. An engine designed with a good quench area (like an M20B25) doesn't leave a lot of room between the piston crown and combustion chamber. 5-6mm? that's like a 1960s inline-4 with flattop pistons..

lol

[LJ851]

Have you disassembled your oil pump? Did you check your rods big ends and rod journals for roundness/taper when you built the motor? Are all the oil pump drive parts doing their jobs? How long did it take to build oil pressure when you first started it after the build?

[329jay]

Dumb question, but you did use assembly lube on all bearings and parts that are touched by other moving parts? That'
s gotta be bad part/ assembly/ starvation. what do the valves look like in that cylinder? If it was a timing problem, there would have to be another piston with damage no?

yeah assembly lube used. valves look ok although ive only looked at them not actually checked them. id agree about the timing damageing more pistons with only one thought. this was the tightest bearing so would have had less oil as a cushion. this was the weakest link.

[329jay]

Have you disassembled your oil pump? Did you check your rods big ends and rod journals for roundness/taper when you built the motor? Are all the oil pump drive parts doing their jobs? How long did it take to build oil pressure when you first started it after the build?

havent taken the pump apart yet. but i actually drove this away from the dyno (for a couple of miles) and it still had oil pressure. i primed the oil by hand when i was building it.
and no i didnt check the journals for roundness

this car had been on a dyno once it had been run in just to check afr's. it had been on a trackday and it had done 5 runs down the strip (15sec dead). it had done about 2000 miles. i would say if it was a build problem it would have let go alot sooner. it let go after 4 hours on this guys dyno.

[LJ851]

hmm What was the clearance you measured on the offending journal? Detonation is very hard on rod bearings, do any of the other rod bearings show contact?

Also, the dyno is harder on an engine than real life but the stress can be minimized. Did he put the car in neutral as the dyno coasted down after pulls or leave it in gear and let the engine come down with the dyno?





.

[329jay]

a drag racer i spoke to recons its what can happen on a high power motor with loads of nitro. the bearing is the softest bit so under load the bearing flattens out. the bearing starts to squash out of the side and into the crank creating heat to further kill it. he sugested that while timing it the dyno guy went a bit too far and the bearing with the tightest tolerance got wiped out. i like this theary. also this would explain the loss of power with every run he did