JimMueller

iTrader: (9)

These are the Clevite 77 rod bearings out of my previous motor, uppers on the left. The uppers/lowers are not matched in the order they came off the motor. Based simply on the photos, I'm looking for educated opinions on how many miles are on them, and what caused this wear.

killernoodle

What rods? And what clearances were run on these bearings?

mvvette97

iTrader: (18)

I would say your crank is oval "out of round" and needs turned. I seen the same thing on an old ford 302 and the crank wasn't true.

Blksnshn

I've also seen this after overheating.

Roar

iTrader: (2)

When the top half, but not the bottom of the bearing is worn like that it is usually the result of a high load from the piston/rod assembly. the particles coming off the the top half will contaminate the lower half.

Possibly some slight knock over time due to a lean condition or bad gas.

JimMueller

iTrader: (9)

I don't know what the clearances were during assembly, but I am told they were approximately .0055 after tear down. Rods were Eagle 6.098" LS1 rods. Edit: piston-to-bore clearance was .0055, not sure what the rod clearance was.

The same local shopped prepped this same crank for two consecutive motors, and a different local shop prepped the same crank for it's next life. Jeremy Formato tuned the car and I always used premium fuel.

Since nobody guessed, I'll tell you this motor only had about a year on it, maybe 10-12K miles.

S10xGN

iTrader: (11)

Wow, that's loose! What oil pressure were you seeing?

JimMueller

iTrader: (9)

D'oh, I posted the piston-to-bore clearance accidentally. I don't recall if the rod bearing clearance was measured on tear down.

pwrtrip75

iTrader: (8)

bearings look normal for a high mile engine. Here are pics of the engine im rebuilding in my vette. Thing ran smooth and fine, never really beat.. 160k miles on it. All the bearings looked just like yours. Im Just rebuilding it because I had it out doing other upgrades.

JimMueller

iTrader: (9)

This wasn't a high mile engine.

HotSilverBird

They look overheated to me.

Jim85IROC

iTrader: (6)

I'm not sure I agree with that. These were the bearings I pulled from my 130k LQ9. This is a pic of the main bearing, but the rod bearings looked the same:

KRAZY K 2000 TA

iTrader: (5)

I would have the big ends of the rods checked for them being outta round first.

LS1-450

iTrader: (33)

The tops look OK to me. The top center wear is exactly under the rod where the rod transfers the combustion force into the bearing. The same can be seen in the second example posted from the 130K mile engine. That is the area that sees the highest pressure (combustion force transferred through the small area of the rod); similar to the spiked heal on a woman's shoe making a dent in a soft floor.

There's not enough detail of the bottoms to see if there is an issue. Would have been better if they were matched to the tops. Although, they look OK, as well.

When replacing, make sure to use tri-metal bearings, not bi-metal. Tri-metal bearings have the top layer designed to absorb contaminents. Bi-metal bearings do not. Looks like tri-metal bearings were used. Am just making sure.