ls1 1990 VN

That engines toast....Stroker time

FAST FREDDY

what diameter is the stock rod bolt? is it a 3/8 or a 9mm?

sdobart

Little follow up on this:

Decided not to risk anything while I had the motor opened up. The crank was able to be micro-polished. One or two little grooves still remained in the crank when all was said and done, but the machinist said they wont be an issue. I pulled the heads, pistons and rods out, and bought ARP2000 rod bolts. Two of the tangs on the rod bearings towards the rear of the engine were flattened or missing, AKA the bearings spun. However, the bearings are not visibly darker, so I feel like they only spun a little or for a short while (caught it really soon after it started happening). From what I've read, these bearings get oiled before the rest do (oiling from rear of the crank towards the front) and the front bearings looked fine. So this leads me to believe it was not an oil starvation issue but a rod bolt stretch issue caused by high RPM (6900 bouncing off the limiter, stock 2001 rod bolts). Combustion chambers and cylinder walls look mint - you can still see the crosshatch. There is no visible bearing material anywhere in the motor, just in the oil pan. I used a dial bore gauge and micrometer to check the big ends for OOR - all were within spec . Mic'd the crank and bought Clevite P main and rod bearings (standard clearances). Plastigaged the motor and everything checked out. Re-assembled the lower end, cleaned out the oil pan and pickup many, many times to ensure all debris was removed. Pull all new valve seals in the heads, re-installed my dual valve springs, and installed the heads.

Motor is fully back together now, had to struggle to get the clutch and pressure plate to line up because I lost my alignment tool, but now all that's together too. Dropping the engine/trans into the car on Monday. It's a swap project (into an e36 M3) so I probably wont fire it for another few weeks. I'm gonna run some cheapo oil through it for initial start-up and then drain it right away, then proceed with a 500-1000 mile break-in period after that.

BoostedLT5

iTrader: (1)

Did you figure out where that spring came from? I just found the same thing, although smaller and more beat up, in my oil pan.

2000PewterT/A

I'd still check them and the crank itself, I have seen some bad bearings but these may have taken the cake for a non-blown up engine.

sdobart

It was a small spring from a valvespring seal. I replaced all the valve spring seals.

I mic'd the crank and had it micro-polished and mic'd it again. I pulled the pistons/rods and checked them for OOR and they were within spec. Rebuilt motor with standard size bearings, all clearances are good.

oakley6575

iTrader: (3)

Holy ****, that was an eye opener. What bearing clearances did you run during the rebuild?

sdobart

Mains: .0016 - .0017
Rods: .0018 - .0020

Aluminum block. Polished crank, stock clearance bearings. Rods are a little tight I think but it's a street driven motor so I think it'll be fine. That's with plastigage, which I expect to read a little tight.