Mitsubishi 3000GT & Dodge Stealth Forum banner

To replace bearings or not?

2K views 25 replies 9 participants last post by  FlyingVR4 
#1 ·
Pulled the trans on my VR4. Bellhousing covered in oil (on the inside), looks like the rear main seal is bad. So, I need to drop the oil pan. Oil pressure is a bit low, oil pump has 30k on it. 176k on engine.

Part of me wants to do the bearings. The theoretical plan was to do a stroker or 74 swap eventually. But the engine is otherwise in good shape. I've read some horror stories about changing the bearings in-car.

Thoughts?
 
#3 ·
First, do you feel comfortable swapping them?

Second, do you actually have low oil pressure? Stock gauge? Oil weight? Or are we just a 3/s paranoid?

If you can answer those questions honestly then I bet you know your answer.


Coop
 
#4 ·
1) I don't feel one way or the other. I've never done it before, but I'd also never changed a timing chain before last month on my BMW. But the BMW hasn't exploded yet. The difference here is I've heard a lot of horror stories

2) I may just be a 3/S paranoid. I don't have a real gauge, just the stocker.

I should probably just wait until it's time for a new engine.
 
#7 ·
Hey, while you have it apart and up in the air you might as well. The oil pump is only half of what makes good oil pressure. Bearings are the rest. They arent hard to change, just time consuming. Put new seals front and back. Keep that synthetic INSIDE the engine.

-SP
 
#8 ·
Pull the caps and cradle, have a look.

If they look good (post pics you need second opinion) leave well alone.

They were built with select fit bearings from new..
 
#9 ·
The select fit bearings is one of my questions, is there a way to tell which size I need before ordering or disassembling?

I'm probably a few days or more from having the pan pulled, want to get the flywheel off first, confirm the leaky rear main (pretty certain it's leaky anyway), and need to disassemble the old transmission that I'm parting out.
 
#11 ·
I am a noob... can someone explain the select bearing thing? does that mean that instead of getting tolerances ideal they just decided to have a stack of bearings, which they pulled, picked, and placed on the factory line?
 
#12 ·
That's more or less right. There are different size bearings picked to get the right clearances depending on how the crank and rod/block sizes turned out to be.
 
#13 ·
I've replaced the bearings in the car before about 5-6 times on different motors without any issues usually during the 120k service. As long as there isn't abnormal wear on the bearings you'll be ok. The lower half of the mains will show the most wear. I found copper showing a number of different times which was why I swapped them out. I prefer to use Clevite 77 bearings since they've worked well.
 
#14 ·
talk about cranking out cars fast from the factory... Crazy to consider how much more attention goes into a proper rebuild.
 
#15 ·
It's not really "cranking them out" when the clearances are as close to perfect as you can get with select fit..

It's a Japanese thing, all sportsbikes.are built the same way with select fit, putting a bearing in that "will do", or putting the exact size in to get best oil clearance are night and day different..
 
#16 ·
So I pulled off the #6 rod cap, figuring I wouldn't like what I saw. I was right:







You definitely notice some scores in the crank and on the bearing, and the bearing does seem to be worn.

Questions:

1) What does everyone else think of those pictures? Do they look as bad as they do to me?
2) Are they too far gone to consider replacing?

The score marks are what have me thinking that I probably am too far gone to consider replacing the bearings without an engine rebuild. Somewhat of a shame, as the cylinders still have their cross hatch in them. Rings seem to be in fine shape. I haven't pulled the girdle yet, I figured I wanted to check a rod first.

While I am most of the way towards having the motor out of the car, I don't particularly want to rebuild the engine right now. Especially since if I do a rebuild, I'd like to do a 6G74 or a stroker (or even better... a 6G74 stroker! :D). My goal was to get another few years (ideally 25k miles more) out of this engine.
 
#18 ·
I'm not convinced on pulling the girdle just yet. Any thoughts on whether I could safely consider replacing them? Scoring observed in the crank? It's visual only, can't feel it.
 
#20 ·
So is the consensus that I need to pull the girdle to have an idea of whether or not they're actually in need of changing?
 
#21 ·
Its hard to tell wear/damage from posted pics. Since you can see some scoring you know there is wear, but as donniak notes they do look "normal" for a higher mileage engine. The typical test I have used is if you fingernail can "feel" a score mark, then it needs attention. Since the cap you took off shows wear, yes, I would open up the rest and inspect.

-SP
 
#22 ·
Good advice. I'll pull the main girdle next and see. Fingertip can't feel the wear on the crank, I'll double check the bearing. The main difference I notice on the bearing is from where the coating is still there to where it's not.

More pictures to come...
 
#23 ·
Dropped the girdle, as promised. And as expected, not thrilled with what I saw.

The #3 main bearing looks the worst, but the #4 main on the crank itself looks the worst. The crank picture is of the #4 main. The #3 bearing you can see copper on. The #1 bearing doesn't look that great, either.

#1 and #2 Main Bearings:



#3 and #4 Main Bearings:



#4 Main on the crank itself:



So, what's the consensus? Change the bearings as-is, pull the crank to have it machined, or just put it all back together and keep driving it?
 
#24 ·
That doesn't look that bad. I had #2 and #3 mains showing copper all the way across the width of the bearing and I swapped them without issues. As long as your fingernail doesn't catch on anything you should be good. It would hurt to try and clean out any oil in the engine. You can do some cleaning of the oil galleys. Some dirt can get in there with the new bearings and look like scoring.

Center mains are usually spun because of excessive detonation. If you spin a rod bearing it's usually because of the lack of oil.
 
#25 ·
That don't look bad for that many miles on a turbo engine, I would replace bearings, check clearances and use good assembly lube, torque everything correctly, fill the oil filter with oil and give it some break in time.
 
#26 ·
That's some excellent news, I'll try replacing them. My fingernail doesn't catch anything on the crank. A few things on the bearings, but minorly so.

Would the general path be to buy a set of normal bearings and some plastigauge first to check everything? If it needs bigger bearings, then I buy the next size up? What sort of assembly lube does everyone recommend? And I'm assuming my FSM will have the clearances and torques, need to look at that. Clevite bearings?

I had a feeling the bearings weren't terrible, so it's good to know that others agree since I don't have familiarity with these engines. At 176k with the cross hatch looking good, bearings will hopefully keep me going a while longer.

Thanks for the advice and answering my questions.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top