Chevrolet 216 235 (early) main bearings? The same?

[Lynn Eades]

Alex, I'd suggest locating some post war (commercial branded as opposed to NOS military) this should come up with steel backed precision bearings. (std from 48 on)
It is probably worth the extra money for a recently made set, from a reputable manufacturer.

[Alex van de Wetering]

they are oval shaped

Mike; do you mean the radius of the bearings is bigger than the radius of the caps? I guess that's a good thing....as it clamps itself inside the cap, rather than around the crank, right? (wishfull thinking maybe )

Did you use the NASCO bearings for your C8 at the time?

Lynn; thanks again for your ideas. Maybe, getting a proper newly made bearing kit is indeed the way to go, but I have some leads, one of them a very good offer from Mike, so I want to see if this could be the solution for my engine.
But I agree...with so many wrong descriptions of NOS bearings sets around, it could be wise to spend some extra cash on a set from one of the Chev parts dealers in the US instead.

Talking about oval shaped bearings......Do two bearings shells clamped together by the caps from a perfect circle?......or an oval, with shims needing to be added to get the result to be a perfect circle?

Alex

[Lynn Eades]

Alex, I am not 100 % sure about the shims, but logic says they are left out with the precision bearings.
These bearings are made to fit a given size bore (tunnel) a part result of the factory line boring of the block when machined.
The precision bearings when paired do not form a perfect circle in this situation as they are usually "sprung" to some degree.(Is this what you have Mike?) This helps them hold in place during assembly (before the caps go on) I think this is the "nip" part of the motor reconditioner's term "nip and crush"?

These bearings also have "crush" Basically when the cap is pulled (torqued) down, the ends of the bearings at the split line are crushed together, forcing the shells into a tight fit with the tunnel bore. This is important as it stops the bearing from rotating in the bore, and it achieves a metal to metal surface contact, essential for heat transfer.
To follow on, the block bores and the shell backs should be cleaned with a solvent and only fitted when perfectly clean and dry.
BTW. the locating tab would not stop the bearing spinning and in modern engines the manufacturers don't use them.

[Mike K]

Originally Posted by Alex van de Wetering

Mike; do you mean the radius of the bearings is bigger than the radius of the caps? I guess that's a good thing....as it clamps itself inside the cap, rather than around the crank, right? (wishfull thinking maybe )

Did you use the NASCO bearings for your C8 at the time?

Lynn; thanks again for your ideas. Maybe, getting a proper newly made bearing kit is indeed the way to go, but I have some leads, one of them a very good offer from Mike, so I want to see if this could be the solution for my engine.
But I agree...with so many wrong descriptions of NOS bearings sets around, it could be wise to spend some extra cash on a set from one of the Chev parts dealers in the US instead.

Talking about oval shaped bearings......Do two bearings shells clamped together by the caps from a perfect circle?......or an oval, with shims needing to be added to get the result to be a perfect circle?

Alex

My C8 has the original babbit lined rod bearings, I removed a few shims from each cap and it's been fine. I polished the journals before re-assembly with a fine emery cloth .

A good engine machinist will fit the new bearings in the caps , then he bolts the bearing caps down and tightens to the torque specification ( no crankshaft in place ) , then he measures the bore of the bearing with a accurate gauge . The measurement tells him what size to grind the crank to , normally they allow about .001"per inch of diameter for clearance . eg for a 3"diameter journal, they aim for a .003"clearance

Measuring the bearing bores after the caps have been tightened down ( no crankshaft in ) is very important . I think a slight oval is acceptable.

I think Lynn explained the crush concept well. Anyway I hope the NASCO bearings fit .

[Maurice Donckers]

Alex , I found several sets 0.30 , and 0.40 in my stock .