JC316

iTrader: (1)

This is on my 92 corvette. I head what I though to be lifters ticking, so I tore the car down to change them. While I was in there, I put in an LT4 hotcam and some comp magnum 1.6 roller rockers. Got it back together and took it for a drive. 30 miles later, I had zero power and the oil temps were around 280*F. Dipstick was covered in metal, so I tore it down and found two spun rod bearings.


Rather than rebuild, I opted for a 120K LT1 out of an Impala SS (I know, but I was thinking about selling and getting a C5 anyway). Took the pan off, oil was dark, absolutely no metal to be seen, no play in the rods. Swapped over the heads, cam, pickup tube and oil pan from the old motor. Got it all back together and had **** poor oil pressure, roughly 5-10 PSI, ran it like that for maybe 45 seconds. Found out that I didn't seat the oil pump drive gear properly, replaced that and oil pressure was fine.

Took it out for a test drive, power felt good, oil temps were a tick higher than normal, but no big deal. Drove it 14 miles and once again the power was headed downhill and the oil temps were rising. Sure enough, a ton of metal on the dipstick. Haven't gotten it back out yet, but smart money is on the rods again.

Did I just have a run of bad luck, or is there something with these LT1's?

hrcslam

Sounds like something else with the car is messed up. Maybe poor oil return from the heads?

JC316

iTrader: (1)

Oil return from the heads is fine. Could the cam be interfering with the oil? Seems like this all started when I got it.

96capricemgr

iTrader: (1)

IMO you caused this both times, the first time maybe it was dirt or the like. The second time 45/seconds without oil pressure.

Was it tuned for the cam?

93M6Formula

Not common at all, doesn't mean it doesn't happen though. I think it's just bad luck. I've been spinning my cam only LT1 to 6400 with no problems.

sweetbmxrider

iTrader: (13)

It certainly is common for high mileage lt1's to **** rod bearings. You seem to have a rain cloud though.

ahritchie

iTrader: (1)

Yikes...must have done something wrong in the cam install or not had clean parts/work area doing it.

Why would you take a step back from an aluminum headed 4 bolt main real "corvette motor" To a heavier iron headed high mileage 2 bolt main cop car LT1?

That was a mistake #2 IMO...A corvette deserves better!

96capricemgr

iTrader: (1)

He said he swapped the heads.
The intake/crank/rods/pistons/block castings are all the same,for a given year so it was a perfectly reasonable decision.

ahritchie

iTrader: (1)

Whoops...didn't catch that, still a shot in the dark of how well it was maintained, and sorta high mileage for a replacement engine.

JC316

iTrader: (1)

Wasn't dirt contamination the first time, but I may have mistaken an early rod for the lifters. There was no metal yet, but they could have stretched. I agree on the second one. The gauge showed pressure, but who knows if it was getting to the rods.

Yeah, I got a chip from PCM of NC.


The area was clean and the install was good. As stated later, I swapped all of the corvette stuff over, only thing I used was the 2 bolt block. Wouldn't have done that if it was a numbers matching car, but the engine has clearly been changed once already.

Yeah, with the age of the car and a non original motor to start with, I didn't think much of it. If the cam couldn't have caused this, the first time was just bad luck, and the second time was my own dumbass fault.

ACE1252

Did you check the crank journals/rod end tolerances(for an out of round condition) along with all the bearing clearances?

How about knocking out the oil plugs/removing the allens screws and rifle brushing all oil passages to insure none are blocked?

How about the cam bearings? Any copper showing?

hrcslam

This.

JC316

iTrader: (1)

Nope, on a running motor, I figured that I was OK. My mistake. Cam bearings were still in spec, copper was just barely showing on the bottom of the front bearing.

ACE1252

Well, I don't know if that is a bad assumption. However, with that many miles and the engine apart, I'd spot check a couple.

At the end of the day, the oil film broke down for some reason. The big question is why?

I think Wrd1972 had major trouble when some quality control marks on a new cam clogged up the oil passages to a couple of the mains after a new cam install. In this thread....last post.

http://www.camaroz28.com/forums/lt1-...ctures-713070/

Here are a couple more of my threads when I was diving into replacing the bearings in my LT1.

http://www.camaroz28.com/forums/lt1-...arings-746672/
http://www.camaroz28.com/forums/lt1-...arings-749300/

95_TA_USMC

iTrader: (4)

Possible balancer issue, or out of balance crank? Tightening sequence maybe?

JC316

iTrader: (1)

I normally don't see a balancer take out a bearing in a few miles. Crank is different on the two motors and I never messed with anything in the lower end, so tightening sequence wont be a factor.

JC316

iTrader: (1)

It has to be that hot cam. Every single main and rod bearing is oil starved on both engines. It's the only common denominator, two perfectly good running engines that destroy themselves within 30 miles of a cam swap.

sweetbmxrider

iTrader: (13)

You don't think 45 seconds of no oil pressure had an effect? By all means replace the cam if you think it will help.

JC316

iTrader: (1)

According to the gauge, it had oil pressure, just not a whole lot. Still doesn't explain the first motor either, I had the pan off on the original motor to change the gasket, at the same time I did the cam. No metal at all in the pan. 30 miles after that, with rock solid oil pressure mind you, it torched every single bearing.

That's a little bit unusual don't you think?

Shownomercy

iTrader: (1)

Did you make sure to hot tank clean the heads/cam/pan before running them on the second motor?

Have you measure the journals on the camshaft in question?

Are your lifters trashed?