Main and Rod bearings HALP

[CoopMK3]

Ok the 7m GTE 89 i am buying seems to have a bit of a knock.. My buddy believes that it is the main and rod bearings... It had a slight oil deprive for about 3 blocks so i am believing this is the reason for the slight knock.. Anyone ever swap these out that can tell me how much of a pain in the arse this is going to be to swap out? And if these are messed up i do know the crank will have to be machined.

 

[KicknAsphlt]

Easiest way -- pull the motor and put it on a stand. Plastigauge the bearings, and inspect them for excessive wear/scoring. It's really easy to replace the bearings themselves, but pulling the motor is a bitch. There's a write-up on here somewhere about dropping the lower crossmember and oil pan and doing it on the car....but if the crank has to come out, you're better off pulling the motor. As far as that goes, just have it micropolished if there's no obvious/visible scoring to the journals.

Truth be told, I ran my motor for over an hour with no oil, and when I pulled the motor (had a knock) and looked at the bearings, they looked pretty good....but still need to check clearances and inspect mains. I wouldn't think oil starvation for 3 blocks would kill your motor if you were using a good synthetic...unless you were beating on it.

 

[sethron71]

Ok the 7m GTE 89 i am buying seems to have a bit of a knock.. My buddy believes that it is the main and rod bearings... It had a slight oil deprive for about 3 blocks so i am believing this is the reason for the slight knock.. Anyone ever swap these out that can tell me how much of a pain in the arse this is going to be to swap out? And if these are messed up i do know the crank will have to be machined.

Swapping them out is not necessarly a pain at all. The rod bolts should be pressed in by the machine shop when they rebuild it. Also the rods should be resized and made true again with the more toque and new ARP's. The Mains just simply replace the bolts. Most say line bore the block. Either way if you have bearings coming apart you need to tear the motor apart and have if cleaned heavily to make sure metal shavings have not travelled with the oil.

If no major damage:
Quick fix:
-New bearings but leave the stock bolts with stock torque specs

Proper fix:
-Rebuild motor

HTH,
Seth

 

[CoopMK3]

yeah he didn't travel over 3600 rpm the whol way home which was three blocks i hope i don't have to do a whole rebuild cuz it just got rebuilt

 

[suprarich]

Yes, the proper way is to rebuild the motor including machining the crank. Most any rod knock crank I have worked on has needed some work. Simply changing the bearings is a short term bandage.

 

[Satan]

Inspecting the crank is going to be key. I had a slight rod-knock once in a Celica and we just changed the bearings and it was okay for many more years/miles. It was easy to change 'cause the oil pan was easily removed, but on any engine in a Supra, it'll take a weekend for sure (if things go well).

The bearings are a softer metal and it usually takes ALOT before the crank really gets gouged. You will be able to tell by "streaks" on the crank which would indicate some good metal-to-metal grinding.

Removing the engine itself is about a half day's work (less if you have some experienced help). Search for "Engine removal in 49-steps" and you'll find some help with that.

I have a damaged 2JZ crank that I can send you a pic of what to look for. Best case is that you can just replace the bearings. Second best case is if the crank needs grinding and all it needs is oversized bearings.

If it was recently rebuilt, I would suppose most everything else is fine (rings, seals, etc).

Just my opinion...