Thoughts on new motor build.

[mountaineerjeff]

So I have always been a fan of leaving the 4.0 alone. Obviously the guys around here typically think a little differently, but Ive put down some of the best numbers on the board, so I have to be doing something right. I have seen so many builds on here go terribly wrong, that I came to the conclusion that Im better off not even cracking the the I6 open. Unfortunately I think I have really pushed my luck so far, and think it is probably in my best interest to at the very minimum install a set of forged pistons. Im strongly considering running an aluminum head, not only for the immediate power gains, but the ability to run higher compression, and mainly the weight savings. So, should I go ahead and toss in a set of pistons while I have the head off the block?

Part of me really wants to go all out, and throw a built high dollar 5.1L together, but it seems like guys have such reliability issues once you start stroking these motors. I have over 1500 lbs of n2o ran through my completely stock 4.0l and she is still running like a top. At the same time ive seen a thousand strokers not make it to the 100 mile mark. Then Im thinking maybe for the type of racing I do, Ill just use a 3" stroke crank, bore the motor way out, 60+, and have and short stroke, high bore motor and rev it to 8k+.

So thats why im thinking my best option, at least for now, is if I decide to go with the AL head, to just throw pistons in it while its open. Keep my over head low, while replacing what I believe is most definitely the weakest link in my motor. Honestly Im not entirely sure why I haven't blown one to chunks already. If thats the route I go, what compression should I be looking at? it will be a 4.0l, with a 5450 redline, AL head, and ran on 93, possibly even ran on e85, or even e100. Id like to get as mush power as possible, before I pump the nitrous in. so can we run 11-1 on 93? maybe even 11.5 or 12.0-1?

Its mostly just a late night rant, as I try to gather my thoughts, but anyone, feel free to chime in.

[karl4x4]

In my oppinion, a built that doesn't last have nothing to do with stroked or not but workmanship. It's easy to do a rebuild and slapping a whole bunch of parts that fit together but there is way more to it than that.

[CobraMarty]

HESCO is always 'out of stock' on their alumn head.

[SilverXJ]

Odd... I ordered one for a client 3 or 4 months ago.

[mountaineerjeff]

you ordered one, did it come in?

and yea it may just be the fact that a put together motor is never as good as a factory assembled one, but I have seen high dollar, reputable builds on here go right down the drain. Im just weary is all. I have an extra long block right now, that has some sort of bottom end issue. I could leave the stock 4.0 in the jeep, find out its limitations, while building a all out 5.1L 13+ compression forged motor with the hesco head. then just throw the entire race motor in, after the 4.0 eats it. My problem is, no matter how well it is built, I have trouble seeing it outlast a factory 4.0. Mine has made it through 2 race seasons, (tech 4 because I race mud + track) all while being abused daily and getting 25k miles put on it. I hardly here of a stroker making it through one season. let alone being daily-ed and making it through 4 race seasons...plus offroading.

basically Im just scared to lose the game of cost+return.

[vashxj]

once my 4.6 is in ill drive it to work for a week, we will see how reliable it is. I put 100 miles a day on and im not easy on any of my cars

[karl4x4]

The building shop has lots to do with it. I managed to convince a marine engine builder to do mine (he used to build racing engine and was highly recommended) he found lots of little factory imperfections like the top of the block not perfectly parallel with crank and cam, valves guides not perfectly centred. Oil galleys not completely drilled. It all worked anyway but all those little things are assembly line defects. Even the crank journals wherent all the same diameter. The factory compensated by using non standard size bushings. (Common practice apparently at the assembly line to save time and not have to regrind the crank)Same for connecting rods to mention a only a few. Imagine if I just put the standard bushings on? I am thankfully I paid the extra to have him do it. Marine engines are built for reliability and that's what I was looking for.

[mountaineerjeff]

well I think I have decided to just push the limits of the 4.0 and make the absolute fastest pass possible with a stock motor,then Ill go for the fastest N/A I6 motor, then the fastest I6, before I shoot for the fastest jeep cherokee period.

so in order
4.0L + lots of n2o
(depending on what happens with the 4.0l) 4.0+AL head+ n20
5.xL high compression I6
5.xL + n2o
after that, I may get frosty and build a turbo setup for 5.xL+high compression+boost+n2o

if that doesnt satisfy my needs, Ill eventually find a motor with more cylinders, but before we get to that point, Im gonna find the absolute boundaries of the good ole 4-0.

[karl4x4]

I raced in the 6 cyl class naturally aspirated (sand drags) and the built 4.0 jeep cleaned up all. I haven't pushed my 4.7 to those rpms cause I built it for torque but if built for hp, i imagine it would definitely be a prime contender.

[CobraMarty]

I look forward to your work on pushing the 4.0 and I6 engine.