So I'm real close into buying a 4.0L head for my '90YJ 4.2L engine. People state it gives you a 30-40 HP increase in power to the meager 112HP the 258 I6 has, but I'm having pre-buyer's remorse right now. The 4.0L has ~190HP, and I feel to properly get around in my country, where there's loads of hills everywhere, I need something around 180HP for a car this size and with no aerodynamics to speak of. Really I don't like 2fast2furious **** at all, but it's also horrible to go up a hill at 25MPH at a 55MPH limit zone, going in 3rd gear ~1800RPM, where I can even go higher than the limit with my mom's Mitsubishi in 5th gear. I wouldn't mind going at 40MPH, just something not extremely slow.
So I guess the question is: will the 4.0L head swap suffice, or should I shell out the extra for a 4.0L engine altogether?
4 slow. lol jk. i would go for regearing it and adding some other parts. like a chip and cold air intake, or maybe just get a supercharger. if you want more power go with the hemi swap, a 4.0 will not give you that much more power without spending the cost of a new engine. so if u decide to put in a new engine, go with a bigger v8 or something
1993 ZJ 4.0L I6, White Jeep member #1993 Check out my build thread:http://www.jeepforum.com/forum/f22/krombergs-zj-build-thread-977508
Haha I'd love to do a V8 swap but it's hard to come across engines in Costa Rica. The only place where I can get the 4.0L head and engine offers them for $140 and $500 respectively, both used from '94 XJ's. I'd have to send them in for cleaning, and the swap I would do with a friend. Also fuel economy comes into hand (I know the 4.2 I6 isn't a great example lol) and V8s offer none of that. Anyone with a head swap can comment where problems which I'm having have been resolved with this swap?
My son's '90 YJ has 3:07 gears, and the 4.0 head swap made a huge difference in performance on his Jeep. I have a hard time keeping up with him on the freeway and I've got 3:55's with my 4.2.
The head swap is on my list of to-do's for this summer. Easy install and big result.
Betcha' wish your girlfriend was as dirty as my Jeep!
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Hang on! This is gunna' be a thrill ride of geriatric proportion! RJC#512
Alright so I guess I'll change to 3.55's and do a head swap. Ultimately I want to do a 4.7L stroker but that looks to be more of a 3 year plan. I'm really not that unhappy with my performance, as it's doing fine off road and the car gets me everywhere and never has left me hanging (only once where I ran out of fuel), but this extra performance is just what I need for my DD needs. I've only done the nutter bypass for now, and from what I saw from a friend's Jeep, Team Rush helps a ton as well, so I'll see how much that'll help when I get the parts in two weeks.
its not the rpm that drop your gas milage, i can run at 1200 rpm when my zj kicks into overdrive, but in order to get that low, the gas pedal has to be depressed a lot more. that is how it get worse. and there are plenty of charts on this forum and other websites, and just check to see what would maintain the best ratio