Wcrawford

i haven't opened a main yet. I'm planning on doing that next. I haven't checked the oil pump, but it was brand new.

andyfloyd

OP I'm sorry to hear about your motor. You said that crank had seen a spun bearing before it was rebuilt correct? I bet it was the #1 journal that spun the first time and that bearing was likely not within tolerance, and like others said I bet your stock oil cooler had a bunch of particles in it. Put those two things together and it's no good, definitely find a good OEM crank.

To the people talking about race bearings.... I've been using ACL race bearings since 2005 on the block that is still in my car to this day. That block/crank has been in my old miata as well as my nb that it currently lives in. And it's been boosted for that whole time.... The engine has been rebuilt 3 times in 18 years and the crank has never needed to be ground and I used ACL bearings. Seems pretty decent to me, not saying OEM isn't good but giving actual living proof that the "race" bearings are very good.

Wcrawford

It actually spun #4. It discolored the crank a bit, so it's easy to see which one it was. None of my rods show any sign of getting hot.

I haven't pulled a main cap yet, but I've got a brand new set of mics on the way. So, when they get here, I'll take a look. Someone else on another forum suggested the crank has worn rod journals that are either tapered or out of round.

I did find a possible source for a decent crankshaft, so I'll probably go that route.

Wcrawford

It's for sure rod knock. One of the bearings was fully destroyed, all 4 were scarred.

Wcrawford

Hey anyone that's still watching this thread!

So, i have an update! I cleaned it all up, replaced the crank with one confirmed to be in spec, replaced the bearings, plastigaged them as in spec, reassembled the engine, then finished my breakin. The car ran wonderfully. Had a few hiccups with some leaks, had to put a oil pressure regulator on my turbo oil feed line, couple other things, and i had a couple tuning issues.

But overall, the car ran strong and nice. It made it through several hard autocross days.

Then, halfway through my last autocross day, rod #1 bearing gave up the ghost. On a run where my codriver beat my best time after i was beating him the previous 3 runs.

But this time, i think i found the problem. When the engine is hot, injector #1 leaks. It doesn't do it when cold. This fits with my tuning issues where my AFR is dead steady when cold and all over the place when hot. At idle it would hit an afr of 10, which is as low a my gage reads, and at low boost (lik 1 psi) it would bounce between 13 and 16. So, my thought is that it would suck in extra fuel from a clear leak under high vacuum and blow some of the fuel out that leak under boost. This caused that cylinder to lean out and detonate enough to destroy my rod bearing.

I've pulled my engine and checked the bearings and sure enough, #1 is gone. The other rod bearings have a tiny bit of damage from crap getting in them, but are overall fine.

Does this make sense? The only other thing that i can think of is i do have an oil pan baffle plate and maybe that's causing oil to not return to the sump fast enough, but that seems pretty unlikely.