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weak points of the 4.0??? engine rebuild questions

blazinjames

NAXJA Forum User
so im in the process of looking for a high out put 4.0L to do my first engine rebuild wondering if you guys could tell me some of the weak points of the 4.0?

I was thinking of going with the 4.2L crank and connecting rods for a stocker build

what parts should I upgrade what should I keep stock?
 
I was thinking of going with the 4.2L crank and connecting rods for a stocker build
Do you mean "stroker" or "stocker"? It makes a huge difference in how you build the motor. If you are in fact doing a stock rebuild, I recommend going with the stock parts but having the rotating assembly professionally balanced and have the crank oiling holes chamfered. A well balanced engine will run much smoother and get better fuel economy. Make sure if you are reusing the pushrods they are well cleaned out to ensure good top end oiling. I am not really aware of the 4.0 engine's weak spots other than what I have mentioned.
 
If you're looking to do a stroker, search this forum and street and performance tech. There's lots of good info regarding building a stroker around here, many have done it nd shared their info with us.
 
If you're looking to do a stroker, search this forum and street and performance tech. There's lots of good info regarding building a stroker around here, many have done it nd shared their info with us.
Also jeepstrokers.com (or something similar). They're dedicated specifically to building strokers.
 
i myself would mess around to much with the internals of the 4.0, maybe a mild cam, oversized trottlebody,air intake, ignition system, header, catback hiflow cat ect
 
I wouldn't worry about a high flow cat. I doubt they'd make much of a difference as removing the cat makes very little difference. If you need a new cat and the price is similar, go for it, but I wouldn't spend extra.
 
the #6 piston seems to be a issue
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:repair:
 
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look for a 99 and up intake manifold, highly reccomed edge products. I usually hear Im crazy for saying this, but I belive it makes a difference...go with a trottle body spacer (helix) if you have an extra hundered to throw around. Screamin' Demon makes a sweet ignition system that allows you to open spark plug gap to .065 or somehwere around there. Yella terra makes awesome (and bulletproof) roller rocker arms. These are the things ive noticed gain notable amounts of horse and torque. Always, stick with the usuals too (header, intake ect). Dont just slap a K and N on and expect greatness. remeber, whenever your building a motor (or modifying what you have) to upgrade both ends of the spectrum. Example, with an intake and throttle body upgrade, a good exuast upgrade should follow. If a upgrade is preformed on spark/ignition, include a fuel upgrade to match. 96'+ (not sure of the year, maybe older) dodge neon injectors are a direct swap and provide much more fuel. id say how much but lb but im unsure of 4.0's stock numbers and i dont wont to say unless im sure. i think its in the ballpark of 4-7lbs more.
 
I thought of putting a stroker in my 91. But the original stock engine has 340 000 kms (~211000 miles) and still starts every time and has ok power. I am just going to go with what I know works.

And there is way less work when matching parts up.
 
I highly recommend you buy a complete stroker kit from a reputable manufacturer because there is alot of science behind making it all work. People who try to reinvent the wheel typically lose a substantial investment in the process.
 
I'd be more concerned about protecting your investment. Put all this money into a stroker but use the stock cooling system? Probably not good. CSF 3 row radiator, high flow water pump, new T-stat. I've seen lots of low oil pressure threads... maybe a high volume oil pump? It seems like most 4.0s are pretty bullet proof, but the systems around them aren't the greatest. Keep it cool and keep it well oiled and it should last you. Like mentioned above jeepstrokers.com is a good place to start. To add to the above post its good to research different brands. Titan is one brand that comes to mind which some people aren't too fond of, while others like ATK. What makes an ATK different from a Titan?
 
I'd be more concerned about protecting your investment. Put all this money into a stroker but use the stock cooling system? Probably not good. CSF 3 row radiator, high flow water pump, new T-stat. I've seen lots of low oil pressure threads... maybe a high volume oil pump? It seems like most 4.0s are pretty bullet proof, but the systems around them aren't the greatest. Keep it cool and keep it well oiled and it should last you. Like mentioned above jeepstrokers.com is a good place to start. To add to the above post its good to research different brands. Titan is one brand that comes to mind which some people aren't too fond of, while others like ATK. What makes an ATK different from a Titan?


My stroker stays cool with a stock cooling system. Goatman runs a stock cooling system in his competition buggy, and it kept his stroker cool through two King of the Hammers races.

Poorly maintaned systems will not keep any AMC 6 cool, but being a stroker will not make it run any warmer.
 
My stroker stays cool with a stock cooling system. Goatman runs a stock cooling system in his competition buggy, and it kept his stroker cool through two King of the Hammers races.

Poorly maintaned systems will not keep any AMC 6 cool, but being a stroker will not make it run any warmer.

stock radiator?

i believe the stock radiator on my 89(no a/c, no aux fan) was single core and could not keep up with cooling the engine during the summer at idle. replaced radiator, never a problem since.

sorry, but the stock set up was not up to the challenge on MY 89. only change i made back in the early 90's was the radiator
 
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