crank

sorry couldnt post in the righ place, kinda new to motor work, but will the crank have a number on it? i'm lookin at buying a 4.2 crank guy says he "thinks" its out of a 87. i'm i'm right the 87-90 hade the serpentine belt and is a bolt up on my xj. correct?

you can use the 4.2 crank with the right combination of rods and pistons. It's more than just drop the crank from the 242 and bolt the one from the 258 in. Use the search, there's a ton of articles about this.

All of the 4.2 cranks will work one way or another, but the 87-90's I believe had the right snout on them that didn't require the spacer.

There was a post a while back showing all the snout lengths and counterweight specs on the various year cranks, try to find it.

Also, saying "bolt up to my xj" makes me think you're under the impression that you're gonna drop your oil pan and toss this crank in...so not going to happen.