4.0l build

Rocky.ca · 10-03-2007, 10:12 PM

I just bought a 4.0l engine with around 130 000kms on it. I want to clean it up really good because im doing basically a body off resto of my tj as a fun summer project. I want to try and sort of build up the engine over the winter. I am not looking to do anything extreme like stroking it or anything but i want to re-build it and add a bit of power in the process. Is this feasable for an average backyard mechanic, and is it worth it? should i just clean it up, paint it and leave the internals? what have you guys had best luck with? what kind of stuff am i looking at when doing a rebuild? anybody have any links to a rebuild guide?

built_amc · 04-01-2009, 09:58 PM

with 130,000 on a 4.0 i would drive the hell out of it for at least another 130,000 before doin a rebuild. thats just been my experience.

**the88thpianoman** · 04-01-2009, 11:08 PM

Honestly, if you're going to rebuild it, just stroke it. No need to do anything extreme, but change out the crank and rods from a 4.2, and get some sealed power 677 pistons. The rest of the rebuild will be unchanged. Port and polish the cylinder head if you're feeling up to it. Without overboring or anything like that, you'll be running a 4.5L stroker. No need to change fuel injectors or anything concerning fuel delivery. You'll benefit from an exhaust sytem and a hi flow intake. Extra benefit from a bored out throttle body. And those are the things you'll be doing anyways if you're looking to squeeze a little more power out of the 4.0. Especially on the 96+ 4.0, if you're going to rebuild it anyways, you might as well just stroke it, especially since you're looking for a little more power.

spiderman637 · 04-04-2009, 07:29 PM

x2. The parts for the stroker can be had relatively cheap. I priced out a 258 crank and rods a while ago at O'Reillys for around $300+core if the didn't accept your 4.0L crank. I also heard Kieth Black makes custom pistons where you use the 4.0L rods. If your search JF you should be able to find the rest of the info on those.

twinsticker88 · 04-12-2009, 01:12 AM

i just stroked my 4.0 to a 4.7, theres a little more then just crank and rods that goes into it.

jeep795 · 04-12-2009, 10:16 AM

if you just do the crank and the rods though, you can get away with out changing anything with fuel delivery but you might run into a knock. it's pretty cheap to shave down the deck though. either that or just run premium fuel if the problem helps. i scored two 258 motors off of this site a few years ago pulled the cranks and got a couple strokers out of it. i pressed the rods from the pistons myself to cut back on cost though. but i don't see why not to put a 258 crank into it. all you have to worry about is the neck of the crank. you can either run a spacer for the vibration dampener or you can have the neck shaved down. i used to see 258 cranks on ebay all the time. it's an easy install. well worth the time and slight bit more money for a lot more horsepower.

also depending on the year crank you get you can run into two different versions. there's one with, crap... i think 8 counter balances and one with 4. there's pro's and cons to each one. the lighter version will have quicker revs. and the heavier one is better balanced and helps with low crawl. obviously if you're using one of these cranks in a newer motor, 96+, you need to look up on advanced adapters for a new pilot bushing. or have a new one turned by a machine shop. there's alot of write ups about these motors. alot.

spiderman637 · 04-13-2009, 06:54 AM

Quote:

Originally Posted by twinsticker88

i just stroked my 4.0 to a 4.7, theres a little more then just crank and rods that goes into it.

I'm sure you're right here, but just curious, what differences did you run into? I've heard you can go all the way from low-buck to real high dollar with these stroker builds.

jeep795 · 04-14-2009, 08:46 AM

if i remember correctly, if you bore 30 over you end up with a 4.6, if you bore 80 over and get a custom crank and pistons, you can have a 5.0. there's all sorts of combinations out there. the 242's are pretty adaptable motors. just to build a run of the mill stroker with crank and rods it will either run you the cost of a new crank and rods, maybe the price of someone switching the rods and pistons for you. or if you buy a donor motor. i'd suggest having the deck cut and a custom head gasket. otherwise the quench is too high.