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stock 4.0 vs 4.2/4.0headMPI vs. 4.6 Stroker

MomoJeep

MomoJeep

Basic User
City
Seattle
State
WA
My priorities are:
(1) cost / ease
(2) reliability/longevity. (4.0's can go for 300k miles!)
(3) Runs well and good mileage
(4) Power / torque - I was pretty happy with my 4.2/4.0headMPI. Maybe a bit more power on the highway would be nice, but not a big priority.


A straight 4.0 seems to be the easiest and simplest. My concern is that the torque/power will be a bit lacking. I'd like it to be at least as strong as my 4.2/4.0headMPI was.

To rebuild me current 4.2/4.0headMPI seems tricky... as I need a good 4.0L head and Clearwater was NOT a solution. An Edelbrock Alum head is around $2000. And i need the compression ratio and tuning to be right to not burn more valves(?)

Stroker: Expensive? I've heard that don't have the same longevity/reliability?

Thoughts?
 
4.6 Stroker has my vote. But they are pricey. I just had one built by Lee Hurley (HESCO) in Birmingham, AL. I couldn’t be happier.
 
Based on your stated priorities, I would go with a stock 4.0HO. Yes, you'll lose a little bit of low-end torque, but you can make that up with gears. You'll certainly have more power at the higher end, which will make freeway traveling a little nicer.

Are you stuck on keeping a straight six? Everyone likes LS swaps these days, but SBC swaps are still viable, cheap and easy. Even a stock 350 would level you up power-wise, and if you wanted to warm it up a little, the possibilities are endless.

Food for thought! :thumbsup:
 
For what it's worth, a factory 4.0HO is a pretty good fit in a CJ-8 for driveability.

However, if you want more power 4.6 is way to go too. I re-built a 4.6 stroker for my rig, it's the way to go to get a decent power increase without breaking the bank. There are a couple ways to do it though, one cheaper, one more expensive but you will get a little more bottom end torque.

The easiest way is to use the 4.2 crank, 4.2 rods, and your 4.0 pistons.

The other way is to use the longer 4.0 rods, and then you need a special piston with a custom pin height, and those pistons get expensive. It's supposed to make something like +5-10 ft-lb of torque on the bottom end. But the cost for 1 piston is damn near the cost for a whole set of 4.0 pistons. I ended up going this route, but only because that choice was already made for me. I wouldn't go this route if I built it up from the ground myself.

I bought the engine already built real cheap, low miles, but developed a "noise". It was basically locked up when I got it, you could turn it free in either direction, but it would stop when #5 approached TDC. Ended up someone had tossed a 3/16 machine screw in the guys intake and it busted up #5. Cracked the piston, cracked the cylinder wall, and chewed up the head. I had the cylinder re-sleaved, the connecting rod checked out okay, and luckily I was able to find the same piston. Put it all back together with a 4.0 HO head I had. I used the factory YJ fuel injection but bumped up the injectors to 24lb (stock YJ is 23lb I think) from the advice of a friend of mine that had done this before. Worked out real well, very torquey on the bottom end. Does tend to run a little rich when cold, but not horrible. It would probably benefit a slight tuning on the fuel curve. I put 89 octane in it, static compression ratio is in the ball park of 9.4:1, and running the factory YJ camshaft.

With any engine build, the more power you put into it, the less longevity it's going to have. I would have to say though that the 4.6 stroker, when done conservatively, is still pretty reliable. I've only butt-dyno'd my engine, but it's definitely stronger. You can look up build results on youtube, but a build similar to mine should be picking up something like 60HP 60-70 lb of torque.
 
I went the affordable and easiest route and swapped in a plain 4.0. Best thing I have done on the Scrambler. Would the 4.6 have had more power? Sure. But this motor is dead nuts reliable (knock on wood). Plenty of power for what I need it for. And at the proposed cost of the 4.6, I would have bought a 360 and done that instead
 
Did a '97 XJ 4.0 with anticipation of going 4.6+ stroker, which is in process now.

Do not do the Edlebrock head, they have casting issues that they can't/won't figure out. Go read up on social media for Newcomer Racing. They are high-power 4.0/stroker folks and were all excited about these heads and found out that they all (literally) have cracking issues and have officially stopped selling/supporting them as a result. I was thinking about going that route on this stroker prior to finding out how much work the PO did with porting the stock head and read up on them there (I'm going to use their reusabe exhaust/intake manifold)

On the stroker, I am going with a Holley Terminator X to run it because it's basically been shown that the stock MOPAR ECU can't properly adjust enough to fuel a stroker properly and there are lean issues on at least the #1 and #6 cylinders.
 
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