What's the most HP for a 4.0?

JJacobs said:
I don't know about that Dino- it's not like the Jeep 4.0 is a diesel, the rods weigh no more than a v-8 rod. Pistons for a 6, bore size considering, will weigh the same as for an 8. I checked the specs on the first 4.0 v-8 that came up, the 290 hp Rover motor used in the 97 Jag XJ8 and it has a paltry .6mm less stroke.
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That's true but here's one interesting fact. Many of today's big turbodiesel truck engines are straight sixes so that's gotta tell you something; large capacity (particularly undersquare) straight sixes are torquers and secondly, they're also very durable.
If you want to build a high revving engine you give it as many cylinders as possible (like the F1 2.4L V8's), make the stroke as short as possible (keeps piston speed down), use a flat plane crank, and make the whole engine as light as possible F1 style.
 
in a nutshell, build the 4.0 for maximum hp and torque under 6k and keep your gears at 3.55 unless its a full drag car. (3.55's hit speed limiter (116) in 1:1 trans ratio before redline)
 
j99xj said:
This has probably been brought up before but what if someone used an AMC 199 crank in a 4.0 block?

This would be the smallest stroke (3 inch) with the biggest bore (3.88 inch) combo which should offer the best overall horsepower. This is exactly what Honda has been doing for years building oversquare motors. This would give 3.5 liters.

Naturally this would reduce low rpm torque but I believe that to be irrelevant when you can easily put lower gears in the axles.
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Does it bolt right up?
 
hmmmmmmmm......now to find a giunee pig
 
BBeach said:
What kinda rods you gonna put in there? I wonder what the power outputs would be with just these and if other things need to be done. I guess a better question is where are you going to find an engine that old?
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Rod lengths are the same as the 4.0 at least according to http://en.wikipedia.org/wiki/AMC_Straight-6_engine.

Well I guessed a 4.0 fully tricked out could make 250 hp, so if I had to guess again a destroked 3.5 liter engine might make 260-270 at well above 6000 rpm.

The age question is a good question that I have absolutely no answer for. This is probably why 99% of people who want to mod their engine go for a longer stroke because it is readily available.

Note: I'm just discussing what COULD be possible with a destroked engine, I'm not planning on doing it myself because I'm an off roader and I need my low end without excessive rpm. Also I need reliability which high revving engines aren't as good at providing.

I would stroke before I would destroke for my daily driver/off road Jeep.
 
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j99xj said:
Rod lengths are the same as the 4.0 at least according to http://en.wikipedia.org/wiki/AMC_Straight-6_engine.

Well I guessed a 4.0 fully tricked out could make 250 hp, so if I had to guess again a destroked 3.5 liter engine might make 260-270 at well above 6000 rpm.

The age question is a good question that I have absolutely no answer for. This is probably why 99% of people who want to mod their engine go for a longer stroke because it is readily available.

Note: I'm just discussing what COULD be possible with a destroked engine, I'm not planning on doing it myself because I'm an off roader and I need my low end without excessive rpm. Also I need reliability which high revving engines aren't as good at providing.

I would stroke before I would destroke for my daily driver/off road Jeep.
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I havent looked at the info yet, but if the rod lengths are the same, but with a shorter stroke, wouldnt you need to do work with the block because the piston would end up being lower and you'd have a low CR? I havent thought about it much but i think there's more research that needs to be done. With gas prices the way they are this could be an interesting alternative. Slap a small turbo on that thing then you'd be all set. party1:
 
The CR would be ~6
 
I like this idea, although id love a torque monster 4.6L as well. But with gas the way its been lately, and most likely in the future, this could be a more viable option. Someone in that thread said the 199 crank is forged, so boosting is an option too, especially with the lower CR.
 
The 199 crank was not forged. There is a rumor that Tony Navarro ran a forged 199 crank in his AMC 6 powered indy car back in the early 60's but the crank was NOT a factory item. All AMC 6 cranks were cast. The 12 counter weight cranks from the late 70's are the strongest based on what I have heard from AMC 6 drag racers. There is a guy that races a 4.0 based rail that revs to well over 8,000 rpm but you cant do that on a street motor. Its OK to pass through the harmonics of the crank (trussed, radiused, 4 bolts) but you cant stay there very long or the #5 rod journal will break due to torsional harmonics in the crank. Road racers have the most experience with the crank problem, drag racers can usually pass through it but eventually the stress catches up with them and the crank still snaps.

John
 
CW said on the other thread "This would be a much faster reving engine, and because the 199 crank is forged it would have a much higher redline." Just kinda took his word for it.
 
Dr. Dyno said:
It's a smallish capacity I-6 (3.2L) with an all-forged bottom end. That's how it can survive 8000rpm.
The Honda CBX-1000 engine has small cylinders and with a tiny stroke, the piston speed is reduced so it too can survive very high revs.
The bottom line is that a big capacity I-6 by nature is a torquer, not a revver, simply because it has bigger heavier pistons, a longer stroke, and thicker heavier rods than a V8 of the same displacement.
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I built a couple of CBX motors that would rev to well over 10K...a stock one would come unglued at that range....the problem was a horrible rod lenght to stroke ratio and spindly stock rods.....a wheelbarrow load of 20's shipped to Venolia and Carillo took care of the problem....but they weighed way too much to be really fast....but they sounded real good...:sunshine:
 
Maybe this photo will *boost* the thread some? Boost being the keyword.. ;)

dsc00549lo5.jpg
 
NXJ said:
Maybe this photo will *boost* the thread some? Boost being the keyword.. ;)

dsc00549lo5.jpg
Click to expand...

Yup, seen that pic a while back.......^ when are you going^ to pic up them two pencil and sketch in the rest of the project! :D

Flash.
 
Sorry to disappoint you, but the motor doesn't belong to me - just had it in my photo archive. :)

I believe there's a guy named "stealcherokee", "steelcherokee, "tealcherokee" or the like, on here that is building it (if his not finished?)

I seem to reckon 600 lbs/ft being his target. Yummy.
 
NXJ said:
Sorry to disappoint you, but the motor doesn't belong to me - just had it in my photo archive. :)

I believe there's a guy named "stealcherokee", "steelcherokee, "tealcherokee" or the like, on here that is building it (if his not finished?)

I seem to reckon 600 lbs/ft being his target. Yummy.
Click to expand...


There is two of them building it..........I just thought you was his partner in crime:D

Was just tying to see if there was any more pic's........Progress on it or if they had given up on it.

Flash.
 
NXJ said:
Sorry to disappoint you, but the motor doesn't belong to me - just had it in my photo archive. :)

I believe there's a guy named "stealcherokee", "steelcherokee, "tealcherokee" or the like, on here that is building it (if his not finished?)

I seem to reckon 600 lbs/ft being his target. Yummy.
Click to expand...
Like most great projects, he quit before he finished. I believe hes working on a hugely lifted xj now
 
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