Big Dave

I stiil have my oil pan off, and my new rod bearings should arrive Monday. What is the procedure for changing the rod bearings? Do I need to remove the crank? Can it be done with just the oil pan off?

I've searched the archives, but I have not seen anything about the specific process how to change the bearings. Perhaps it's easy, but I'd like to find out in advance and make sure I don't screw it up.

John Veninger

Dave,

You do not need to remove the crankshaft, but you will be rotating the crank. Move the crank so you can access both rod bearing nuts. Take the rod cap off, sometimes you'll need to tap the rod stud with the wooden end of the hammer to release it. Push the rod/piston up the bore so the studs clear the crank journal. You may want to move the crank shaft a bit so you can now pull the rod back down to remove the bearing.
Install the new bearing and coat the surface with engine oil before putting the rods back on the crank journal.
Important notes: only rotate the crank clockwise, use NEW rod nuts, be careful not to scratch the journal with the rod stud, and keep everything CLEAN.


Side note- Am I the only one who has a problem with the spell check working on the forum? It works only 1 out of 10 times for me. I get "Error on page" in the bottom left side of my browser.

mark kibort

As you may have heard, scots racer spun a bearing after 2.5 hours of running and about 1 hour of racing. crank looks pretty bad, but its all the material from the bearing welded on the crank. I suppose there is no way to polish the crank while in the enigne?

anyway, bearings are easy to replace, but use Johns suggestions. also, dont put assembly lube on the bearing part that fits in the journal. only on the surface that mates to the crank. Scots engine had a grease film on the bearing as it attaches to the rod journal and the engine bearing holder. that would (could) insulate the bearing from being able to dissapate heat back to the engine and could cook the bearing. (could have been what happened with our failure)

do you have the engine out of the car , or are you doing it from underneath?
Did you go in there for something else and since you are in there , doing the bearings?

just curious

MK

John Veninger

Mark,
There may be damage to the journal besides just the bearing transfer.

IF the rod is still round (that's a big if), You may want to try and cleaning off the journal w/ some 600 and 1200 sand paper. Use a plastic gauge in several spots and see if you can come into tolerance.
Otherwise it's an engine pull and hope there is no cylinder/piston damage

Big Dave

Mark:

My engine is out for a top-end rebuild following a timing belt failure. The only things left to do are to get my intake and covers powder coated and change the rod bearings. I should be back on the road in May.

V-Fib

as per the WSM's.
I waited a few days longer for reassembly because I forgot to order them. It would be a heart breaker for the unthinkable to happen by using the old nuts.

Big Dave

I've got new rod nuts coming, too.

mark kibort

acutally, i forgot the main issue here. its not the mechanical damage , its the metallurgy. At the temps it took to melt the bearings, the rods are TOAST! (literally) they are black in color and this heat obviously would transfer to the crank and weaken it. so both, the crank and rods are done. 2 new rods, and a new crank is what the doctor ordered.

Now, do i re-ring? (since ill be in there anyway) or just rebearing the rods and maybe leave the main bearings alone too. any comments here?

we are going to yank the parts out this week.

now, how do you get the main front bolt out, now that the engine is out of the car on a stand? I think air tools can get it off, but we need to flywheel lock to get the 250ftlb torqued bolt out! maybe my NOS bottle and air tool can do it for a quick shot!

MK

Benton

I would think that WYAIT you should do the rings anyway; it's not that hard once you are in there. I'd hate to think what would happen if you were lazy about other bearings and another failure occurred as well. Therefore, I think I would check the main bearings too.

John Veninger

Mark,

Check the pistons that were on the bad journal. Usually the piston gets beat up pretty bad when the bearing goes.
The front bolt will come off with a good air gun.
The mains should be OK, but there was a lot of metal floating around that motor, so a quick check should be done. The oil cooler is another area of concern.

mark kibort

thanks, so check main bearings and re-ring cause we are in there anyway?

im so sick of turning bolts!!! already. (especially pulling engines on my back!)

and, its not even my car!!!!

MK

sublimate

Dave, slip short pieces of hose over the rod stud threads when you remove the caps to keep from nicking the crank.

John Veninger

Check the mains.
How many miles on the rings? Did you do a compression test before the rod failure.
I guess if in doubt, then change them.

Good luck and I know all about being on my back doing 928 work, especially on a cols cement flolr in the middle of winter. What we do to race

John Veninger

Dave,
Sorry for taking over your thread!

Big Dave

My new bearings and rod nuts just arrived. I'll be installing them tonight. Thanks everyone!