peckerwood1986

I am rebuilding a motor and it's already been cut to 30 over so I would have to go to 40 over. I live in Las Vegas and it's very hot here in the summers. My question is is this to much to cut it. I've heard the cutting it this much makes it run hot. Also the rebuild kit I'm looking at is this one. http://www.northernautoparts.com/part/ek-ek0027b

Any opinions or thoughts would be appreciated

almido

As an engine mechanic I can tell you that an extra .010" bore won't hurt a thing. It's minimal. Overall, if you take a hose and wash the leaves out of your radiator fins once in awhile it will make more of an impact on keeping it cool than limiting yourself to .030" overbore.

Watch out how far they have previously cut the crankshaft. If it's at .020" or .030" now, trade it in for a crank done at .010".

I looked at the Northern page, I'd suggest you buy the upgrades. Better branded bearings are very important. Try to get the better brand cam bearings as well, also very important. The high volume oil pump will do you well. Because they have a pressure valve built-in your pressure won't go crazy but they are able to flow more volume which means more engine cooling, especially of the valve springs (which should also be new). A HV pump may wear over the years like any pump will, but instead of reducing volume to half normal, the HV will reduce to a level equal to a new standard pump in the same time.

Ask for or order extra, a set of Brass core plugs (freeze plugs) and you won't need to replace one in a couple years.

Pay EXTRA for Fel-Pro gaskets !

Have your machinist go over this kit with you. Don't go CHEAP !

Keep in mind that when the vendors put together a "Master Kit" they always combine the absolute cheapest parts they can find on the international market. Always pay extra for name-brand parts.

Don't scrimp on assembly lube, break-in oil and protocols. Break it in slowly and change the oil and filter several times. Don't use synthetic oils until after you pass 2-3 thousand miles. Use WIX or NAPA Gold (made by WIX) oil filters.

I suggest Rotella oils as they have more lead than car oils. Ask your machinist.

IF YOU DON'T HAVE THE MONEY OR TIME TO DO IT RIGHT, YOU WON'T HAVE THE MONEY OR TIME TO DO IT OVER.

Best of luck with it....

Dan


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almido All My Dough 2001 XJ 241k Miles unmolested so far.....

Fred/N0AZZ

I agree with the prior post completely the 40 over is nothing to worry about at all just use a good machine shop for all your work, one that's been around for a while and has newer equipment. The 10/10 crank is fine also if a no go there find another crank to use. Have it line honed as well while there.


As for parts "Always" but the better ones you really do get what you pay for there. Pistons, Rings, Bearings, same for the head get good springs, valves, seals, guides you get the picture.


By all means let your machinist know that you want quality parts and ask him for his help/input. Most shops in my area would assemble that 4.0 for about $3-500 with a warranty and you choose what parts are used and what machine work is completed, not like a lot of the "Rebuilt Engines" you buy from some.


You failed to mention a year on motor or of the XJ its in/going into could be other things apply. Cost is soon forgotten as the quality keeps showing, where when you put $hit in you know what coming out.

peckerwood1986

Thanks guys. It's a motor out of a 95 but it's going in my 96. I was planning on ordering the upgraded parts. This is my first time doing motor work I've done all my own work to it as far as custom y-arms and sye and what not. The shop I'm using comes recommend by a lot of people out here so I feel pretty confident about them

CCKen

peckerwood,


Going .040 over may not be a good idea.


The Mopar Replacement Parts Jeep Engines manual says the following:




Boring and Milling Specifications


Because it is a thin wall casting design, the 4.0L can only be over-bored ,030" (maximum), although .020" (maximum) is preferred. Regardless of the amount of overbore, if the engine is to be used for high output racing purposes, the cylinder wall thickness should be checked to be sure the block doesn't have a bad case of core shift. The cylinder wall thickness should be the same all the way around or thicker on the major thrust side of the cylinder bore; that is, passenger side (as installed in the vehicle).

Firestorm500

I have more experience with small-block Fords, which also have a thin-wall casting.

.040 over is the absolute limit; .030 or less is much better. At .060 over, you run the danger of cutting into the water jacket, so you can see they are pretty thin.

260-289-302-351W can sometimes run hot at .040 over. Some people sleeve the block at .040 and above. Classic Mustangs, especially, have a small radiator and grille, much like our XJs.

The other guy probably has a lot more experience than I do, but I don't recommend a high flow, high pressure, or high volume oil pump. The stock one is fine. You want the oil to stay in contact with the bearings long enough to pick up and carry away heat.

Oil pressure is created by bearing clearances. Having a high pressure pump will not cure worn bearings, and may even accelerate wear.

Jeep Driver

If you are really concerned........have it sleeved.

Or find another block.

Moncheche

I literally just walked in from my first drive in the 4.0 I rebuilt.
Quality is quality when it comes to bearings and gaskets. The guys are right when it comes to that.

You say you're already 30 over on the cylinders, do you know why it was taken there? Previous damage, choice, bad machine shop?
What do your crank and rod bearings say on them?

Ah... have fun. These are fun little boat anchors.

Talk to your shop and see what your options are.