Thread: Replacing crank bearings

OK so I figured out what my lubrication problem was - the assembly lube that I used to put my valve train together broke down into the oil, and caused it to degrade to the point where it was not properly lubricating the moving parts anymore.

500 miles later, I have to replace my (brand new) cams and my rocker arms due to the wear, and I have some rod knock going on as well, as a result of the same problem. So now I have to go back in and replace them again as well, but I'm thinking that if the rod bearings have had that much wear, I should probably take care of the main bearings as well while I've got her apart.

Here is my question:
As a preventative measure, can I simply replace the bottom half of the main bearings so that I don't have to drop the entire crank (and of course the tranny along with it)? I figure that the bottom half of the main bearings gets probably 90% of the wear since the pressure comes from above and pushes down on the crank. Maybe my logic is flawed, or I'm missing something here, but if I only replace the bottom half, I won't have to drop the entire crank, so I'm willing to try it if you guys give me a green light.

Thanks for any input, and sorry for the long post.
Rick

i'm a firm believer in if you are going to do it, do it right. i think it would be easier in the long run to drop the whole crank anyway, since you are replacing all bearings associated with the crank.

I agree with Katana. Do it right (upper and lower), or don't do it at all.

As an aside though, what type of assembly lube were you using?!

yeah that would be just stupid to do just half the bearings, sorry man but i figured you would learn from your first mistake of not doing it right, i would never use assembly lube with anything on my motor, use freakin engine oil, period..... Do it right and dont do it again is the only way to go. and yes that means pulling everything, might as well pull the motor if you havent already.

Actually, I used assembly lube that came with my cams from Brian Crower. The key is not to overdo it. Just a thin coating on the key metal to metal parts would suffice.

Cool. Thanks for the advice, guys.