4.2 stroker?

[kevmacallan]

I have a '90 Wrangler with the 4.2. It needs a rebuild; ~300,000 miles and major blow-by and power loss. I'm planning on putting the 4.0 head and EFI on it. I'm wondering if I should put a different cam in it/ bore it more than the minimum/ do anything else that would be a good idea since it is being rebuilt anyway? I'm not building a rock crawler, it will be used for trail driving and street driving, possibly a daily driver as long as the commute isn't too far. It's lifted 8" right now, and I will be upgrading the axles at some point and putting air lockers in. Thanks for any input!

[kevmacallan]

Oh, and I am looking for an engine rebuilder. I have seen several online, just want opinions on which ones are recommended/ good guarantees/ cheap/ etc. Thanks!

[Mgardiner1]

For engine rebuilders, look for something local. And why does the subject say 4.2 stroker? Sounds more like a 4.2 rebuild is what you are after. Slapping an EFI head on it would definitely be beneficial but does not turn it into a stroker

[kevmacallan]

I was/ am under the impression that the stroker engine =4.0 bored + 4.2 crankshaft? Please forgive any ignorance, I don't mean to offend, and I'm an amateur at best when it comes to automotive. Since I have the 4.2 (with the 4.2 crank, obviously), I was thinking that the main difference would be the bore job. So I am trying to find out if boring it more than I need to for a simple rebuild is a good idea. Again, if I posted in the wrong section, or used improper terminology, I apologize. I just want to get my Jeep back, I'm sure you can all understand that. And want to do it right.

[lafrad]

Well, to do the "upgrade", you will have to pull the 4.2 apart, get the crank cleaned up/reground.

Then, find a 4.0L block that can bolt into your Rig, along with a set of 4.0L pistons. Send the new pistons, along with your old pistons and rods, off to the machine shop to get the 4.0L pistons installed on the 4.2L rods... might as well get the rods cleaned up and a setup with new bolts too.

the 4.2L block does NOT have the meat in it to take an overbore to 4.6/4.7L. otherwise all you need to do is find a set of 0.030" over 4.2L pistons. you'll gain a little displacement, but nothing significant.