67rschev

Just as the topic says , has anyone ever spun a crank bearing ? Not a rod bearing , but a main journal crank bearing . Doing an overhaul and they look OK , and ohhh ehhhh , they are pricey !

M758

Nope,

However worn main bearings can put less oil to the rod bearings. The reason is the mains are directly feed with oil from the pump. The excess oil is then sent through the crank to the rods. So if you have loose open main bearings they can leak more and thus pump less oil to the rods. Result is you spin a rod bearing with worn main bearings.

If the crank is coming out then change the mains. If you are doing things in the car and block and crank are still in there then it is fine to get by with rods only.

cjeckert

Your better served by plasti gaging them to see how they really stand then not doing it now and running into issues latter.

67rschev

Not a big fan of the plasi gauge . Every time you torque babit bearings together , they seem to tighten up and egg the clearence a few 10 thousands .

dv8nxs944

Lol don't even get me started, one of the 2 motors i destroyed spun about every bearing it it,dont remember which one though

67rschev

No worries now . I sourced the main bearings for 180.00 . Also , i am using the 83 rods , is it ok to use the late model cast rod nuts on these rods ? Is loctite 574 the only sealant to use on the crank girdle or is there any new style sealant that you guys are using ?

924RACR

You're lucky you can still get 'em...

Zero10

Loctite 574 or 518 is fine for the crank girdle. I prefer 518 since it is stronger and easier to apply.

As for the mains, it is very rare that you see excessive clearance on them, with ONE exception. The thrust surface of the middle bearing. It is very common to see this one worn WAY out of spec, allowing the crank itself to pull forwards/backwards. This is the only bearing that prevents the crank from moving in this direction and it is typically in very bad shape after 20+ years.

I don't know about the rod nuts. IIRC the new nuts are spec'd for all rods, but watch me be wrong on that one.

KuHL 951

So true. I pulled a crank from an engine (91K) that resided most it's life in San Francisco with all those steep hills and clutch abuse. The mains were still perfect but crank end play was almost out of spec. When I pulled the thrust bearing it was very worn and the wear pattern on one side was really obvious. New mains are a good insurance policy if you have the motor out already.