Who here has actually built/run a Jeep/Amc 4.0 stroker?

Looking for experiences, costs, the parts list you used, how it ran, etc.

I'm seeing people making 200whp/250wtq doing silly things like machining their pistons down to stay with a compression ratio low enough to work with their stock ECU and electronics. Make me wonder what would happen if you embraced the compression and high-test fuel and added Megasquirt.

The backstory to this is that i'm enamored with the idea of an LR4/L33 swap in my XJ, but am wayyyy too cheap to spend that kind of money and/or effort. Working with the motor i have is always way easier.

Any good reason for me to be thinking about any of this? Absolutely not. The 4.0 in it now could use some love. Has a cracked manifold, healthy tick that sometimes is loud enough that i wonder if it's a knock, and seems to make really crappy/lumpy power below 2400rpms. Pulling the motor is in its future likely within the next 12 months (i don't put a ton of miles on it, so even if it is a knock, it'll be just fine for another year, because 4.0), and if i pull it, chances of another 100% stock motor going back in are very slim.

Hemming's Project HMX has been running one for years and goes over the complete engine build. I've sold lots of AMC parts for guys building them, but haven't actually assembled one myself... yet.

4.2L cranks are getting hard to find. All the reman ones have dried up and the last one I got was crap. It was welded and turned .040” with crap in the oil passeges plus when we check end play it was .08” over max spec. It was from Crankshaft Rebuilders btw. You can get a new one from Scat but it’s going to set you back $450 plus bearings.

You can use 4.2 rods with 4.0 pistons but you will have a poor rod ratio. Few of stock piston but compression will be around 9.7:1

It looks like most people are building them with 4.0L rods and custom pistons ($600?). Keith Black makes stroker pistons to use with the 4.0 rods but the pistons will sit .020 down the hole and mess up quench. Yeah you can deck the block but you will need new pushrods.

Most aftermarket cams have the narrow 4.2L lobes unlike the wider 4.0L ones. I think the Mopar performance used wide lobes if you can find one. Lots of reports of people wiping out lobes. Might be due to the narrow lobes or people using springs rates that are too high. There are no drop in replacement springs that will work with a big cam. Most options will need the spring seat cut to work.

FYI the 97+ computers can be reflashed

Thanks so far, guys.

I'm not against a $450 crank if that's what it takes. The LR4/L33 will cost me $5-6k all said and done on paper, so probably actually $15-20k. (LOL! Probably $6-8k) So, as long as this can stay a couple to a few grand under the V8, it'll stay a viable option.

When you say "but compression will be around 9.7:1" is that saying that like it's high? Or just milquetoast? There seems to be not great information on motors on Cherokeeforums, so i'm guessing i'm looking in the wrong places. Without knowing anything else about the motor, i was maybe looking for 10.5-11:1.

How bad is the rod ratio using 4.2 rods with 4.0 pistons? Does this really matter for something that will probably never see more than 5000rpms?

Would you suggest a reflash over Megasquirt? There's been rumors of Horsepower Tuners supporting these, at which point i'd probably just do that. Beyond that, i have an inherent distrust of reflashes, and unless told otherwise, would stick to Megasquirt.

I’m fine with 9.7 compression with good quench is ok with a cast iron head and 93 octane but other jeep guys think it’s on the high side or want to run 87 octane. I think part of their problem is they are still using the stock computer and have don’t nothing to control timing. http://www.jeepstrokers.com/forum/ is a better resource for these engines.

I have nothing against running 4.2L rods and don’t think the rod ratio will be too big of a deal. First stroker I built used them but I sold that project shortly after getting it running so I don’t have any true feedback for you. If I was to build another one I'd run Scat forged 4.0 rods for $300 since the cost is about the same as having a used set of rods reconditioned with new bolts.

Megasquirt will work but you will need MS3 to use the stock crank trigger wheel. Another option is to use a 36-1 trigger wheel mounted on the front of the crank and MS1 or MS2. As for wiring in MS it could be a pain to keep the gauges and transmission working properly unless you install it in parallel. Having the stock computer tuned might be easier if you can find someone familiar with JTEC. With an SRT4 map sensor I think it can even be tuned for boost.

oh and incase you want to add a turbo I'll just leave this here:

http://www.boostwerksengineering.com/40L-Turbo-Manifold-_p_17.html

Yeah, the attempts at using the stock computer are what i think a lot of this "oh god don't do that" stuff comes from.

Thanks for the forum link, i'll mess around on there.

Scat forged rods for $300? Yeah that's fine, i'll just plan on that. Doesn't that bring us back to the piston issue, though? Is there somewhere that already has the files on the custom pistons necessary?

$300 rods, $450 crank, $600 pistons, that honestly doesn't sound terrible.

MS3 is a go, i'd want working knock control anyways.

Transmission not a concern, mine is a 5spd. Gauges... maybe care a little. Not against a parallel, but also wouldn't be 100% against just rolling all Autometer gauges or something.

JTEC.... must read up on that.

If i do forced induction of any kind, i won't bother with the stroker, would just stick another 4.0 in there, local guy sells rebuild shortblocks for reasonable prices.

Check out Bulltear for pistons. Its honestly been a while since I've shopped for them so I don't have any specs handy. Jeep stroker forum should be able to help with piston section. I think Scat might even offer a stroker kit with pistons.

http://www.bulltear.com/catalog/product_info.php?cPath=21_34&products_id=242

So i'm googling and..... Holy crap this E36 M3 is CHEAP.

Looks like i can get a full 4.7 rotating assy in 10.7:1 flavor for around $1500 with forged all the things.

Maybe you can talk Swank Force Industries into getting a Mazda F2T to whatever trans you've got bellhousing adapter? I heard on the internet that the F2T makes those quoted power numbers look pretty weak by comparison.

pres589 wrote: Maybe you can talk Swank Force Industries into getting a Mazda F2T to whatever trans you've got bellhousing adapter? I heard on the internet that the F2T makes those quoted power numbers look pretty weak by comparison.

The way it delivers it isn't really what i'm looking for in this situation.

http://www.jeepstrokers.com/forum/

I learned quite a bit here a few years ago when I was looking into this. Also pirate4x4 forum has good tech. There was a guy on there, I think his name was something like yjncorey, he was a 4.6 guru, he built them for offroad race rigs. But go on there and search, don't talk. Those guys can be brutal.

  You can use the 258 rods. I think most people were using injectors from mustang 5.0s. There were two different 258 cranks, the older ones had more counterweights, and the newer ones with less are supposed to outperform them in every way.

Didn't Edelbrock release a new aluminum head for them as well?

Appleseed wrote: Didn't Edelbrock release a new aluminum head for them as well?

Yep. That's part of the reason for considering this. I bet i can make more real world power out of a 4.7 stroker than i would with an LR4/L33 for less money.

Most of the internet lore says you can hit 300 ft/lbs torque pretty easy.

gearheadmb wrote: Most of the internet lore says you can hit 300 ft/lbs torque pretty easy.

I think that's drastically understating it. HorseE36 M3 4.6 strokers being run on stock ECUs with stock heads are doing 250ftlbs to the wheels.

I'm thinking 350ftlbs to the wheels by 2000rpms.

YJ_and_Corey on Pirate4x4, that gearheadmb referred to, wrote a 7 page pump gas "Stroker Recipe." I've got a .pdf of it if you can't find it elsewhere.

Swank Force One wrote:

gearheadmb wrote: Most of the internet lore says you can hit 300 ft/lbs torque pretty easy.

I think that's drastically understating it. HorseE36 M3 4.6 strokers being run on stock ECUs with stock heads are doing 250ftlbs to the wheels. I'm thinking 350ftlbs to the wheels by 2000rpms.

I usually try to understate things when I'm quoting speculation from shaky sources that I am getting from my own fuzzy memory because I'm to lazy to look things up before I start running my big yapper.