[CaptainFleXJ151]

Checkout my latest project: the build up of a 4.7 stroker for my next Jeep project. One thing I didn't mention on the page is that i will also be doing a dual throttle body setup with a custom intake manifold.
A Stroker Story
Add it to your favorites if you want to follow the build up.

 

[dorfs]

It sounds pretty cool. First, DO NOT bore a 4.0 more than .040. There isn't enough room, and the marginal displacement difference isn't worth re-sleeving the cylinders. Second, using the newer style d.i.s. pack on an older block isn't a good idea. The block castings are different. There isn't any mounting holes for the d.i.s. pack in the older block and unless you work for Chrysler, you will never get a custom flash for the newer JTEC controller. Third, I wouldn't build it for horses, but torque. The horses will come with the extra displacement for free, and torque is what you want for low end grunt. Next, I wouldn't get too radical with the cam. I have used both the Mopar stage 2 and stage 3 cams with matching springs, and the stage 2 is much better! Using a cam profile that has a lot of overlap won't have any manifold vacuum at idle. This really messes up the computers ability to correct for mixtures at idle. Remember most of the fuel delivery is determined by the m.a.p. sensor, and with no vacuum at idle from a wild cam will shoot your low end torque all to hell. If you really wanted to improve the stroker using a 4.2 crank, have the quench area set correctly. This will allow a higher compression ratio without the detination. This is basically done by decking the block a whole bunch, and using custom low compression pistons. Last, I would re-think using two throttle plates for the much easier 5.2/5.9 Magnum throttle plates. These will allow more air, and still have i.a.c. , t.p.s. , and m.a.p. sensors that are compatable with the 4.0's harness. If you really wanted to get fancy and pick up a bunch of displacement, have the crank offset ground down to a SBC's rod journal, and use Chevy rods and pistons!

 

[Jaffer]

You never cease to amaze me, dorfs.
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[ryeguy]

We've successfully bored 4.0l's to '0.060-over without any problems, even in strokers. The local machine shops list the block is good for that overbore, and we've found that to be the case.

Some older 4.0l blocks can handle even more than that without resleeving it, you just have to find the right casting.

Quench does have a role, but without finding really dished pistons, you're better off getting pistons from a company like Accurate Power, which uses 4.0L rods and the 4.2L pistons - solves quench and compression at once. Decking the block bumps the compression, and you're already starting with a high number. That said, we've built nearly identical strokers, one will run happily on 87 octane, the other wants 92.

You can also play with different heads, there's at least 4 different combustion chamber sizes. Depending on your exhaust and intake choices, your head selection will be a subset of that, though.

The Mopar Stage 3 cam seems to move the power band up quite a bit in a 4.0l, no experience with it in a stroker.

The offset grind, Chevy rods, etc. is Clifford's recipe. IMHO, that combo isn't worth the additional expense over either a simple stroker, or one with 4.0L rods.

Check out my first go-round experiences at: http://www.bc4x4.com/tech/bryce/stroker/stroker.cfm
That was a few years ago now.

--Rob

 

[CaptainFleXJ151]

Rob, in the very beginning when I first got into Jeeps I had decided to buy an XJ rather than a CJ. The reason was that I wanted to build a 4.7 stoker and have a longer wheelbase Jeep. Your story is what inspired me. And I thank you for that. Your article was the first one I read on the project.
I'll keep in mind the cam when doing this build. Your guys have a lot of good things to say. I would go those routes you all suggested, however my father has build BMW racing engines. He does custom fuel injection systems for the most complicated late model BMW engines with infinately variable cam timings and complex wiring harnesses. These motors are about as tough as it gets, fortunately for me he has over 50 years of expirience also with American cars and other euro. vehicles. With his help we should be able to build quite a spectacular motor. So things like the fact that a late model harness does not hook up, will not be a problem. And a custom throttle body setup that still works with the injection system properly will also be easier. I may even add a lean/rich control in-cab. Thanks for your thoughts, they will be taken into consideration.

 

[ryeguy]

CaptainFlex,

Thanks for the kind words. I've since sold the Comanche, though, and am going bigger: to a full-size Chevy Blazer. No details 'til it's done and driving, though.

Sounds like between you and your dad, you've got the bases covered. Look forward to hear how things turn out.

FYI, we had to go looking for the Mopar Stage III cam, my impression is all that's left is just old stock, and won't be replenished. I could be wrong, but that was the impression I was given.

--Rob

 

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Better stroker info

Just a few notes RE: 4.0's & Strokers. Sonic check that block, if the bores align with the cores you can bore the hell out of a 4.0 (.125"!)
The coil pack bolts to the head (not the block). If you have a hankerin' to run one use a '99-on head. (these have puny exhaust ports, another story)
Mopar's cams are old school, with the same intake and exhaust duration. They also don't feature much lift for the durations available. See http://www.accuratepower.com/Jeep/Parts.html#StrokerParts for some more cams and info. BTW there is a threshold for manifold vacuum before the ECU spits it out. All of our cams will work with OEM ECU's.
SB Chev rods are too narrow on the big end to drop into a 4.0 based engine. You need to have custom rods made. (Along the lines of a SBC blank) to use the smaller SBC rod journal diameter.
Our pistons have nothing at all to do with the 4.2. They are custom made for Strokers using stock 4.0 rods.
Just passin' thru. Any questions, give me a call, MIKE