I want to build an insane 4.0L!

OK, I have my old 4.0 sitting around and I need a new project to tinker with. I want to build something that has as much power as possible but revs as fast and as high as possible. I don't think a stroker could meet these goals but I could be wrong. What cam, rods, and pistons would be the best. How high of a rpm can the stock crank take either the 4.2 or 4.0 ? I would like to push it right to the limit if possible. It would be a NA engine so how high of a compression could I take it with premium gas, I don't want to have to run racing fuel. What about a lighter flywheel? does anyone make one or would I have to have one milled? Any suggestions or comments would really help.

I would build a 4.7L stroker with the 258 crank thats got 6 counterweights (vs 12), 4.0L rods, custom pistons, full port and polish the head, cut in slightly larger valves, roller rockers, a hot cam, Borla header, high flow cat, and a high flow muffler of your choice. High preformance plugs and wires along with a custom cold air intake and bored throttle body and spacer would also be used.

You should be at around 275+ horsepower with the above depending on compression ratio and fuel, but if thats not enough you can go forced induction :cheers: Add a supercharger to that and you can get close to 350hp. I personally would go with a turbo and intercooler with a stand alone ECU and put it on a dyno and tune it. From another thread, somebody ran a 4.7L turbo'd stroker in desktop dyno and made 430hp out of it. Then theres always a shot of "NNNAAAAAASSSSSS"

Check out Dinos home page: www.jeep4.0performance.4mg.com This is where the stroker info is to be had.

AARON

The problem with the stroker is too much spinning mass. I've never driven one but I've heard people mention that it doesn't spin up and down as fast but that could be remedied (kinda) with a light weight flywheel.

I've been thinking about this exact same thing for quite some time. If you keep the stock block, head and crank 6200-rpm sounds like the maximum reasonable revs before you start having problems. Having the crank balanced is a good idea but I doubt you'll be able to squeeze many more revs out of it just by balancing. If you go up to a custom made racing crank then yes you could push it higher but now your talking serious bucks.

Same goes for the head, keeping the stock cast iron poses limitations over an aluminum racing head. I believe 10:1 CR is the max you can get from the stock head even with some savvy polishing, but that's ok because anything above that requires racing fuel.

I like to design an engine by first getting an idea for the power band then find a cam that is best suited for it's needs. Basically build the rest of the engine around the cam, not the reverse. If you're keeping the stock crank (6200-rpm redline) then I would go with CompCams 68-239-4 but it requires headers and short gearing but that's a given for "an insane 4.0". :worship:

Edit:
If you do some research on cams this is a good article covering the basics. Also keep in mind that the 4.0 has similar a bore an stroke to the Chevy 350 so what works for it should work for the 4.0

Bore x stroke
4.00" x 3.48" = Chevy 350 V8 - 349CI (43.6CI per cyl)
3.88" x 3.41" = Jeep 4.0 I6 - 234CI (39CI per cyl)
3.94" x 3.41" = Jeep 4.0, Bored .06" over - 242CI (40.3CI per cyl)

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MrShoeBoy said:

You should be at around 275+ horsepower with the above depending on compression ratio and fuel, but if thats not enough you can go forced induction :cheers: Add a supercharger to that and you can get close to 350hp. I personally would go with a turbo and intercooler with a stand alone ECU and put it on a dyno and tune it. From another thread, somebody ran a 4.7L turbo'd stroker in desktop dyno and made 430hp out of it. Then theres always a shot of "NNNAAAAAASSSSSS"


AARON

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I was the one that did the DD of the turbo stroker, that was a completely theoretical engine, that would have required huge $$$$. At that point a BBChevy would be a much better swap. I wanted to use a turbo on my stroker but I went in another direction, I built it for low end power. A 100 shot is almost inevitable on this project. What kind of CR would I get with 4.0 crank, 4.0 rods, and maybe AP stroker pistons. That would probably get it low enogh for a substantial amount boost.

While the redline for the 4.0 is shown at about 5Krpm, going to about 6K isn't that uncommon. There is an issue with harmonics up around 6500rpm, but there are reports of 4.0's being balanced to spin up around 8k without too much trouble. That 6500rpm harmonic doesn't go away, so it's something that would have to be remembered and "hurried thru" when turning that fast.

However, the principal advantage of the 4.0 is that is makes power at a useful low rpm band, coupled with a nice, flat torque curve.

I'll have to find my design sheets, but I've got a few ideas in the works. I will eventually need to talk to Venolia (pistons) and Manley (valves) for some of the ideas I've got, and a new head casting would be nice, but I'd like to punch and stroke a 4.0 out to about 4.000x4.000, which yields just short of 302ci! This would require an offset-ground crank, but boring the block out that far has worked for Mike Parrish for a while now (Accurate Power.)

Dino's webpage is an excellent source for information, but you may also want to start watching the "strokers" egroup (groups.yahoo.com/group/strokers) for more info, since that's what we're all about there.

You might also want to look up Ed A. Stevens - either here or there - he had a lot of great input on my head redesign project that withered a couple years ago, but I've not forgotten. If Russ Flagle at Indy Cylinder Heads isn't interested, perhaps someone else would be? I need to have a head-shed with Ed on that...

There are also reports of strokers with proper "quench" heights (relation of piston deck height to cylinder head deck surface) running well drinking pump gas, so that's something else to think about. Do a search at "strokers" for info on quench, and some resources are also online.

5-90

I was looking into what headers would allow the engine to breathe right up to 6000 rpm. I believe large diameter header tubes that are short get the torque up higher in the rpm range. Mike Leach headers look like an option but I'm not sure if there's something better that will place the torque between 1400-5700 rpm.

When I race I never use anything below 3000 rpm so I'd imagine peak torque somewhere around 3500-4000 rpm would be good.

5-90 said:

I'll have to find my design sheets, but I've got a few ideas in the works. I will eventually need to talk to Venolia (pistons) and Manley (valves) for some of the ideas I've got...

Click to expand...

I'm also planning to build a high rpm I-6 but racing regulations prohibit increased displacement (except for bore .06" over). What would be a good piston/rod combo for 6200 rpm?