rod bearings AGAIN!

[dan2288]

I spun a rod bearing about 4 months ago. The machine shop cut the mains .25 and just polished the rod journals. It looked fine. I got acl race bearings and replaced the spun rod with a good one. Now, it started making a ticking noise while driving. This morning I took it apart and the rod bearings look pretty bad. There was metal in the oil too. So I kno I need new rod bearings. But what would cause the bearings to get bad again? The car always had plenty of oil and the oil pressure was good. Any ideas ?

 

[JusMX141]

Sounds to me like you're way too rich, flooding the crankcase with unburnt fuel that is ruining the oil's film strength.

Do you have a Wideband? If so, what does your Air/Fuel ratio look like under load and while cruising?

Does your oil smell like fuel when you drain it?

 

[dan2288]

no, oil smells normal

 

[JusMX141]

You didn't acknowledge my Wideband question, so I'm guessing you don't have one.

What is your global injector compensation on DSMLink? With 950's it should be around -52% or -53%.

 

[alansupra94]

You just replaced 1 rod bearing? I was always told if you replace 1, replace and check them all.

 

[dan2288]

no, I replaced all of them. Currnetly Im running 880s with a keydiver chip. That should be fine. I just hope its not crankwalk...

 

[JusMX141]

Something's obviously killing the protection value of your oil and allowing the rod bearings, which normally ride on a thin film of oil, to contact the crankshaft.

The only other explaination would be improper bearing tolerance from the get-go.

 

[dsmkid4g63t]

no, I replaced all of them. Currnetly Im running 880s with a keydiver chip. That should be fine. I just hope its not crankwalk...

if your crank was walking to the point where it was affecting the rod bearings...i think you'd now for sure if you had crankwalk!

 

[silvreclips]

Did you plasti gage the bearing cleaences when putting the motor together?

 

[dsm-onster]

Did you have the big end of the rod(s) that had chewed the bearings originally line honed? Heat will cause the big end of the rod to go out of round. With such tight clearances between the crank and bearing, this can cause enough distortion to eat more bearings. Did you reuse the rod bolts in their exact location? or did you happen to swap them around or put other oem or upgrade rod bolts in?

 

[alansupra94]

no, I replaced all of them. Currnetly Im running 880s with a keydiver chip. That should be fine. I just hope its not crankwalk...

Okay just checking....I think you would know if you have crankwalk....damn you are making me paranoid about my bearings now

 

[dan2288]

I just checked the main bearings and they're worse then the rod bearings. Im thinking maybe the machine shop didnt cut it right. But about the crank walk, would it cause all the bearings to go bad?

 

[dan2288]

Im thinking about just getting a crank and bearings and hopefully it will last a while

 

[dan2288]

Im thinking that the crank wasnt machined right. I put the old bearings back in the main gridle and they didnt fit too good. I had the mains ground .25 and got .25 bearings. If I put the bearing against one side, it doesnt reach the other side. I know they fit right when we put it back together. What could cause the bearings to become like that?

 

[half-cocked]

I just checked the main bearings and they're worse then the rod bearings. Im thinking maybe the machine shop didnt cut it right. But about the crank walk, would it cause all the bearings to go bad?

Check the thrust face if youre concered with crank walk, if should be pretty beat if it walked on you. The only case of crankwalk I ever saw personally went down like this. Started the car, it was slow starting as in it was cranking over slow like a tired battery, a ticking noise and when I was driving it it died. We eventually found out that the crank angle sensor was wiped out, apparently that was the ticking noise. When we pulled the enging apart, rod bearings looked fine as well as the mains with the exception of the thrust face.

Car in question was a 97 GS-t I took for a test drive from a little dealership when this happened, a friend of mine bought it for a bargain basement price and used it as a project car.

Look at the thrust face, and check out the CAS for abnormal wear. It sounds like improper clearances or maybe the crank wasnt properly cleaned after cutting the mains.

 

[half-cocked]

Im thinking that the crank wasnt machined right. I put the old bearings back in the main gridle and they didnt fit too good. I had the mains ground .25 and got .25 bearings. If I put the bearing against one side, it doesnt reach the other side. I know they fit right when we put it back together. What could cause the bearings to become like that?

OK, the way I'm reading this is that there is a gap between the 2 bearing halves when you put them back in the girdle. Did you torque it down? Are they the right bearings? As in are they 4G63 bearings? You can have the crank ground to whatever spec your heart desires, but that doesnt changes the inner diameter of the mains on the block. You should be able to put STD bearings in there and they should have no gap between the two halves.

As far as throwing a new crank and bearings in there, if you overheated and warped the rods and/or mains even a little that might be enough to spin another, not to mention the possibility of bearing particulates that might be cold chillen in the block waiting to give you another reason to put your DSM on jackstands.

 

[dsm-onster]

I just checked the main bearings and they're worse then the rod bearings. Im thinking maybe the machine shop didnt cut it right. But about the crank walk, would it cause all the bearings to go bad?

The issues I raised in my last post would cause the bearings to go bad. Did you check the big ends of the rods before you reinstalled them?

 

[dan2288]

no, I never had the rods line honed. The motor never over heated thou... And the gap im talking about is just using one bearing, from one top to the other. Its hard to explain.

 

[dsm-onster]

Overheating the rod has nothing to do with overheating the motor. You over heat the rod when you spin a bearing. Think friction, no oil, the reason for the bearing failure. Now you have a bad rod. You need to check the specs of the rod after the rod has been heated with a spun bearing.

I could be wrong. But it certainly not good engine rebuilding to swap in bearings after one spun without checking the rods. You check the crank. Check the rods: on the other side of the bearing. Theres enough heat generated by spinning a bearing to cause microfractures in a nitrided 4g63 crank capable of 1000+ whp. I'm certain there could be enough heat to damage the big end of a 4g63 rod.

 

[half-cocked]

Depending on how long you ran it with spun bearings and how hot it got there might be some discoloration too, darker on the bottom of the rod and some blueing. Not sure if blueing is correct term, but if you see if you will know what I'm talking about.

 

[dan2288]

Okk, but the rod that spun, I had replaced. It was the only rod that spun the bearing.

 

[talon187]

why dont you post some pics or everything ?

 

[dan2288]

ill try tomm, I can never get pics up on this forum for some reason