Jeep Strokers

What Main Bearings do i need?

I have a 89 Block and a 258 crankshaft out of a 76 CJ-5 that is turned .010 under. I placed the crankshaft, before it was turned down, in the block with the factory bearings in place and it does not fit, to tight. I am thinking just going with the factory replacement size bearing with the crank turned should be about right.

SOMEONE PLEASE SCHOOL ME ON THIS!

I am working on a limited budget and limited tools (I.E. no micrometer or other measuring device)

Thanks

Hello,

You will need the bearings for your block (89) in a .010 size to match the amount cut off your crank. You can use plastiguage as a very cheap way to verify bearing clearances. It is not as precise as good tools, but close enough for most who are budget-constrained. You can get this from your machinist or any decent parts house locally or even order it online from Jegs, Summit, etc.

You'll need 10 thou undersize bearings to match the crank journal undersize. The '87-'90 Renix 4.0 blocks use the same main bearing part no. as the 258 block.

What if you have a later 4.0. If your 258 crank hasn't been turned will it still drop into the stock 4.0 bearings?

The difference between 258(also renix 4.0) & 4.0 HO(91+) bearings are the locating tangs. Thats it. You need the ones to fit your block. If the crank is turned .010 then those are the bearings you need. It's that simple.

79jeepincj7 wrote:What if you have a later 4.0. If your 258 crank hasn't been turned will it still drop into the stock 4.0 bearings?

Exactly as Russ said, so the answer is yes. The '91+ 4.0 HO blocks need the later style 4.0 main bearings with the locating tangs in the center. The 258 and Renix 4.0 main bearings have the locating tangs offset to one side and won't fit in the 4.0 HO block.