Jeep 1987 YJ Wrangler 4.2 engine swap or rebuild?

[idahoyj]

My dad has an 87 YJ with a VERY TIRED 4.2l. The 4.2 has an aftermarket Howell fuel injection system, that NEVER seems to run right. The fuel injection was installed long before he bought it, 8+ years ago. The Jeep has 30/35 axles with lockers and 4.56 gears. The transfer case has Tera 4:1. Manual transmission has been swapped to AX15. 35" tires.

My dad does not need horse power. He needs dependability and an engine that wants to run, not just stall out. The current set up will barely pull 4wd high on flat ground with the tires aired down which means he has to use 4low. 4low is usually too low for what he wants to do. He does some mild crawling, but mostly just mountain roads and some snow.

We would like to repower his Jeep with as little down time and cost as possible.

Things we are considering-
Rebuild/replace the 4.2l that he already has and hope the fuel injection is more reliable with the new engine.
Rebuild/replace the 4.2l with a reman version and add a modern aftermarket TBI system.
Rebuild/replace the 4.2l but convert to 4.0l head and injection.
Complete swap for 4.0 engine and injection
Complete swap for GM V6.

What would RME do?

 

[Pile of parts]

Seems like it should be easy enough to find a decent 4.0 relatively cheap.

 

[mbryson]

Seems like it should be easy enough to find a decent 4.0 relatively cheap.

This would seem to be the easy way to go? Find a donor rig for a swap and use the whole powertrain/wiring harness? I've always wanted to swap in an XJ 4.0L/AW4 into a YJ for some reason? At least as much work as a Chev V8 swap but factory reliable and good solid auto trans.

Wonder how well a 4.3L V6 from an S10 or similar would swap though?

 

[Skylinerider]

Wonder how well a 4.3L V6 from an S10 or similar would swap though?

Pretty common swap, and with the AX15 that is already in there, it shouldn't be too bad. When I swap out the 4cyl in the YJ for the boy in a few years I'll probably go with a 4.3 and NV4500 trans.

 

[Shawn]

I happen to have just pulled out a 4.2 out of my 86 CJ7, has a lot of good stuff on it.But, if you are talking about a YJ, do you not have a 4.0?

 

[Skylinerider]

I happen to have just pulled out a 4.2 out of my 86 CJ7, has a lot of good stuff on it.But, if you are talking about a YJ, do you not have a 4.0?

1987-1990 YJ's still had the 4.2

 

[Shawn]

1987-1990 YJ's still had the 4.2

Interesting, that I didn't know.

My 4.2 has the 4.0 head swap and few other goodies

 

[Toad]

I have a CJ7 with a 4.2 and Howell efi also. I considered a 4.0 swap at one point. I wanted more power and economy than the 4.0 offered. I also looked at a Vortec 4.3 swap. That is just about as much work and expense as a v8 swap. Mine is now getting a 5.3 GM

If pops is not wanting more power go for 4.0. It will be the easiest and cheapest.

 

[UNSTUCK]

I'd spend a few minutes figuring out the EFI first. Any chance the engine is "tired" because the EFI is not working properly? Don't just expect a new engine to run any better with that same EFI installed. Run a compression check to see where you're at with your engine.

100% no to a GM V6. A V8 is the exact same amount of work. If you don't want the HP or worried about breaking other parts, stay light on the throttle, or throttle it down so you don't have to worry. It's a lot easier to use less than needed throttle then to use more throttle than you have.

What is his budget like?

 

[Gravy]

∆ we put a 5.7 TPI in my wife's 89 YJ. I could never get the 4.2 to run right. Too many goofy vacuum hose on that Carter computer controlled thing that came stock.
We ran a 7004r auto and changed the input on the 231 tcase to fit. Worked well.

 

[idahoyj]

I happen to have just pulled out a 4.2 out of my 86 CJ7, has a lot of good stuff on it.But, if you are talking about a YJ, do you not have a 4.0?

Sending PM

I'd spend a few minutes figuring out the EFI first. Any chance the engine is "tired" because the EFI is not working properly? Don't just expect a new engine to run any better with that same EFI installed. Run a compression check to see where you're at with your engine.

100% no to a GM V6. A V8 is the exact same amount of work. If you don't want the HP or worried about breaking other parts, stay light on the throttle, or throttle it down so you don't have to worry. It's a lot easier to use less than needed throttle then to use more throttle than you have.

What is his budget like?

He's had it in to multiple shops having it tuned and messed with. The engine has tons of miles and the compression is on the low end of acceptable. I really want this to be an easy swap because it will most likely happen at my house. He isn't flush with cash right now since he's building a new home, but I'm sure he could scam a few grand out of the pot for Jeep money once we figure out what direction we are going.

 

[UNSTUCK]

Well the only easy swap is going the same engine route, and it's not a bad idea. I'm really only saying if you're going to put any engine in that's not stock, GM V8 is the best option. Even like Stratton said, an older v8 is cheap and still a great idea.

I'd like more info about your EFI that's not running right. What did those shops say was wrong with it? Have you talked to Howell tech support?

What about just doing an in-frame rebuild on your motor? Slap some rings on those pistons to boost compression. Maybe even swap to a 4.0 head.

 

[gijohn40]

I have a 4 barrel carb and manifold for the 4.2. it came off my cj7. The carb is a holley 390cfm which is built for smaller v6/i6 engines. the manifold is an offenhouser

 

[Bart]

I would vote for at least a 4.3 swap. They are easier than a 4.0 swap, and it's a 3 wire hook up.