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4.0 Rebuild

Fish'nCarz

Fish'nCarz

NAXJA Forum User
Location
Victor, ID
I'm looking for performance rebuild threads and not finding anything not strokers. Not looking to build one of those. Any help would be much appreciated!

Brian
 
So, you want to do a performance rebuild, but not stroke it? I don't really think there's such a thing. I mean unless your turbo or SC it.

You can do a stock rebuild and use all really nice parts. Yellow terra rockers, KB pistons, performance cam, etc. But in the end it's still gonna make just about the same power as a factory rebuild. Maybe a tad more.

In the Jeep world, 4.0 performance is synonymous to stroker.

Two of the more details threads that come to mind are Talyn's super unlucky build (stroker), and Bryson's turbo build. Lots of pics in both.

http://www.naxja.org/forum/showthread.php?t=977237&highlight=stroker

http://www.naxja.org/forum/showthread.php?t=1031285
 
why no stroker? You can easily do one for the same price as a complete performance rebuild, but actually get some gains out of it. Still results in a reliable motor too.
 
There are a few things you could do w/o going stroker. Increase the compression by decking the block and using a thinner head gasket. You will get better quench in doing this as well. Polish and port the head. Stainless swirl polished valves, however there is no reason to go with larger valves. Polish and shot peen the rods. And of course balance the rotating assembly.

If you are going forced induction in the future you don't want to increase the compression.
 
Thanks for the links and input!

My plan is to buy a 2000 - 2001 Limited in great condition with a bad engine and rebuild the engine, then use it as my DD. Want the best performance I can get from a non-stroked engine; both performance and efficiency-wise, and I'd like to keep mpg about the same as stock. It's also going to be my first engine rebuild project, so it's going to be a learning process. I'm also going to upgrade the brakes and lift it a little, upgrade the wiring some, just replace the stuff we know are weak points.

Then I will re-purpose my 2001 Sport for off-road play as an expedition jeep. Need to keep it dependable and durable. Haven't really thought that through yet but a Rock Trac transfer case and more radical engine mods are floating around my head. (And a fridge and on-board shower!) It has lived in Michigan it's entire life, so there is some rust repair that needs to happen as well. I've thought about just selling it and buying another XJ to build, but I've got a real sentimental attachment to this one, and I know its history. It's my 4th XJ and by far my favorite, except I miss the storage shelves in the dash on the earlier models.
 
Talyn said:
There are a few things you could do w/o going stroker. Increase the compression by decking the block and using a thinner head gasket. You will get better quench in doing this as well. Polish and port the head. Stainless swirl polished valves, however there is no reason to go with larger valves. Polish and shot peen the rods. And of course balance the rotating assembly.

If you are going forced induction in the future you don't want to increase the compression.
Click to expand...

What about changing to one of the Mopar performance camshafts?

Any point in changing the injectors if the piston size isn't changing?

I know it's a little pricey, but the Hesco aluminum head promises a lot (and anyway I slice it, this thing is still going to be WAY cheaper than a new car!). I really like their water pump and thermostat housing.
 
I did what you're talking about--I took a good '99 engine, and then dressed it up with a bunch of performance bolt-on parts (ported throttle body, headers and exhaust, better injectors, better ignition parts, etc). You can spend a lot of money on this stuff, $1-2k without even trying (most of it will be the exhaust, but it all adds up). The throttle response is much snappier, and the power reserve is clearly deeper than stock, but it didn't turn into a V8 or anything. A stroker will give you a much deeper power reserve that can be tapped sooner. If you want significant power increases and you have the $2k you should put it into displacement. If you just want to improve the stock setup, you can do it and you will certainly feel it.
 
Fish'nCarz said:
What about changing to one of the Mopar performance camshafts?
Click to expand...
An upgraded camshaft would be a good idea but you may have to change your springs, depending on the lift.
Any point in changing the injectors if the piston size isn't changing?
Click to expand...
Some 4 hole injectors may help in idle and throttle response especially it the stock injectors are dirty. I wouldn't go to a larger injector like a 24 lb/hr one.
I know it's a little pricey, but the Hesco aluminum head promises a lot
Click to expand...
IIRC there was someone that put an aluminum head on a stock 4.0L and didn't see any benefit w/o other mods. To take advantage of the head you need to increase your compression ratio quite a bit. I think you would be better with a worked over stock head.
 
ehall said:
I did what you're talking about--I took a good '99 engine, and then dressed it up with a bunch of performance bolt-on parts (ported throttle body, headers and exhaust, better injectors, better ignition parts, etc). You can spend a lot of money on this stuff, $1-2k without even trying (most of it will be the exhaust, but it all adds up). The throttle response is much snappier, and the power reserve is clearly deeper than stock, but it didn't turn into a V8 or anything. A stroker will give you a much deeper power reserve that can be tapped sooner. If you want significant power increases and you have the $2k you should put it into displacement. If you just want to improve the stock setup, you can do it and you will certainly feel it.
Click to expand...

Thanks!

My goal is not to build a V8, just trying to make the 4.0 L be all that it can be without changing the basics. I know that opening up the throttle body is popular, but if you keep the exhaust pre-cat at 2.25, does it really do more than just cleaning it well?
 
Talyn said:
An upgraded camshaft would be a good idea but you may have to change your springs, depending on the lift.
Some 4 hole injectors may help in idle and throttle response especially it the stock injectors are dirty. I wouldn't go to a larger injector like a 24 lb/hr one.
IIRC there was someone that put an aluminum head on a stock 4.0L and didn't see any benefit w/o other mods. To take advantage of the head you need to increase your compression ratio quite a bit. I think you would be better with a worked over stock head.
Click to expand...

Thanks for the input. You can do a lot to a stock head for $2000!

What about fuel pump and filter? Just replace with stock or is there a better answer? I plan on pulling the gas tank and cleaning any gunk out anyway, so may as well replace original fuel pump.
 
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Fish'nCarz said:
Thanks!

My goal is not to build a V8, just trying to make the 4.0 L be all that it can be without changing the basics. I know that opening up the throttle body is popular, but if you keep the exhaust pre-cat at 2.25, does it really do more than just cleaning it well?
Click to expand...

I recently went to a bored out throttle body, higher flow intake, and an "upgraded" DynoMax cat-back and noticed a definite improvement just in that. The throttle body helps with mid-range power and smoothness.
 
I was thinkin' a frozen, concentrated orange juice can and some riggers tape would work good.

 
There is a lot of power to be made in the cam and head.

I think Eric Filar was pushing close to 300 horses in his non stroked 4.0 before he sold it. I'll see if I can find a thread about his engine.
 
Apparently there is no build thread.

Anyways. You can bring the compression way up, do a big cam and a lot with the head, as well as change fuel management systems - and gain a TON of power.

But that power is in the upper RPM range, and you'll be on 100+ octane gas, and spend a TON of money doing it.

You get similar numbers by stroking it, run on pump gas and can drive down the freeway. That's why everyone does it that way..
 
I am also interested in 4.0 internal performance upgrades. After doing my rear main I discovered my bearings are worse than expected so in the future I plan to do a full rebuild also. My 87 already hauls balls on small tires and low lift without the 4.10s which are going in soon so a smooth powerful 4.0 should be all it needs. I figured a stroker might get a little scary lol. I would plan for a cam and a ported HO head but am still uneducated on quench heights and what causes the engine to ping.
I've heard 9.5:1 is too much to where you would have to step up the octane and piston-valve clearences becomes an issue after ~.060 removed
 
Super mud said:
I've heard 9.5:1 is too much to where you would have to step up the octane and piston-valve clearences becomes an issue after ~.060 removed
Click to expand...

You need to read A LOT more. And stop listening to people who say stuff like this. Specifically the ones who talk about piston to valve clearances having ANYTHING to do with overbore.

I have a 9.5ish:1 compression ratio, .060 overbore stroker. And if that is not enough for you, it has gotten boring and I am looking into adding a blower.

edit: I somehow skipped the line before that where you talk about cam stuff. I would read up a lot more about those as well. It is kinda hard to mess up quench height with a poor cam choice.
 
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One of the best mods i have seen on a Jeep rebuild is to deck the block, make the pistons come up closer to the head, and boost the compression. Not really sure what the limit is on this, but I suspect it may be much like a 292 cubic inch chevy 6, and on those, we run the cold static quench at .025 and it works well. What is the tightest clearance you have ever run a non-turbo 4.0 or 4.7 Jeep engine???
 
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