4.0 to 4.5L

[SilverXJ]

You have to check the cost of regrinding a crank VS a reman that includes the bearings.

You can't use the 258 main bearings in a 4.0 block.

[smbball32]

I went to the shop today. They told me $125 to bore, pull the old pistons out, and press the new ones in. I also went to the auto store. They want about $180 for a new crankshaft with bearings. I'm still looking for pistons, rings, and rods.
Does anybody know where I can find a cheap crankshaft? If the bearings that come with it won't work, would I be better off buying a used one, then buying the bearings for a 4.0L?

[ajmorell]

You have to check the cost of regrinding a crank VS a reman that includes the bearings.

You can't use the 258 main bearings in a 4.0 block.

Meaning you gotta run 4.0 bearings on the 258 crank I'm assuming? Why can't you use the 258 bearings in the 4.0 block?

[SilverXJ]

Because the 258 Main bearing are different from the 4.0L main bearings. Don't recall which part exactly.

[SilverXJ]

If the bearings that come with it won't work, would I be better off buying a used one, then buying the bearings for a 4.0L?

If you get a used one you still may have to have it ground.

[stroked'73]

I was under the assummption that the bearings would interchange - as would the main caps too. The bearings are a different part number because they're a different metal composition.

[stroked'73]

From http://www.bc4x4.com/tech/bryce/stroker/assembly.cfm:


Bearing Selection
The 4.0L and 4.2L engines share the same main bearing dimensions and clearances. However, the main bearings list as different numbers. Should the 4.2L bearings that match the crankshaft be used, or should the newer 4.0L bearings be used? The tech guys from both Federal Mogul and Mopar Performance couldn't help us here. So our machinist looked up in his bearing book, and the only difference is in one alloy. The alloy used in the newer 4.0L bearings was recommended for off-road use, so the decision was easy.

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Since you're going for budget and older 258's ran forever anyway, I'd use 258 bearings if they came with a new crank.

smbball32 - if you haven't already read the entire link above, do so - it's very much what you're trying to do.
Best of luck

[rradford9]

Because the 258 Main bearing are different from the 4.0L main bearings. Don't recall which part exactly.

The locating tang is whats different. The early Renix era 4.0L's ('87-'90) share the same main bearings with the 4.2L. The locating tang on the 4.2L main bearings is offset. On the newer ('91+) 4.0L's the locating tangs are centered. Since you are building a '97 block, you'll need the 4.0L main bearings and can use either 4.0L or 4.2L rod bearings.