crankshaft replacement

Hey. I'm planning my stroker build up and like usual I'm trying to do things the easy way instead of the right way. So my question is this...can I replace the crank in my current engine with a 4.2 crank without pulling the engine? I just want to use my stock pistons for now...so I really don't want to mess with taking everything apart. Thanks.

-Keith

99 4.0 auto 4wd

The problem is that you can't just swap the crank. You also have to swap the rods. It is not a good idea to change the stroke without boring the block. If you do this, each time as the piston goes up and down, for part of the stroke it will be on the old worn (larger diameter) and for part of the stroke it will be on unworn cylinder (smaller diameter).

Pulling the pistons out the bottom to swap the rods is also not a good idea. Even if they would clear, you would have a heck of a time getting the rings on the piston compressed to get the piston back in.

I never even thought of the unworn areas. Thank you for the insight.

You definitely can't pull the pistons out from the bottom of the bores; there isn't enough clearance between the main bearing webs.
If you're gonna build a stroker, you'll need the 4.2 crank AND rods (unless you use 4.0 rods with custom pistons) so you'll need to pull the engine out anyway. As Tom said, you'd be advised to freshen the cylinders with a mild rebore and get the appropriate oversize pistons/rings.
_______________________
Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 181k miles - AX15, NP231, D35c, D30

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Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

I was just going to keep the stock pistons with the 4.2 rods. Then I would have to run premium fuel until I actually put in oversized pistons. BUT.....I guess I'll just do it right the first time. Blah.