Engine Overhaul, What would you do?

Well next semester I'm taking engine performance I and II, which all you do is rebuild and tune a motor, provided by yourself. That being said, I want to get a new engine ready for my '97. It has about 200k on the clock and seems to be making more and more noise as time goes on.

So I'm looking to rebuild/overhaul a newer 4.0 HO, but want to know what I should do, what I should replace, upgrade, etc. I don't want to do a turbo, stroker, supercharger, or anything that would be too costly. This is a DD engine so I want cheap and reliable. But in terms of cams, lifters, ignition, oil pumps, headwork, that sort of thing - What should I look for?

Port the cylinder head and give it a really good valve job. Also you could coat the pistons with ceramics to give it just a little better thermal efficiency.

Yea I've though about getting it ported, I'll have to look into it. I know there is one head that really sucks on xj's, but forget the number.

having taken an automotive course and rebuilt an engine, hopefully they are going to teach you how to tear the engine down, inspect for damage/wear and measure the parts to see if they are within spec and what parts should be replaced just for safe measure. if the parts spec out correctly than there is no need to replace. this will determine what type of rebuild kit you need to buy. some rebuild kits are just seals, gaskets, timimg chain, rings while other kits include crank, bearings, cam, valve guides, pistons, lifters.....

if the block needs any machine work or the possibility the crank is worn, then why not build a stroker. if the engine is in good shape then you will most likely need a basic rebuid kit, but if it needs alot of replacement parts, i would do a stroker.

Hmmm I'll have to do a little more reading and see what's involved. As for the classes, it's engine performance I and II, and I'm also taking engine repair I and II. So next semester will be 16 credits of engines lol. I'm not looking to spend over $1000-1500 on the entire thing though...

DanMan2k06 said:

Hmmm I'll have to do a little more reading and see what's involved. As for the classes, it's engine performance I and II, and I'm also taking engine repair I and II. So next semester will be 16 credits of engines lol. I'm not looking to spend over $1000-1500 on the entire thing though...

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as basic rebuild kit is around $300-$400. if you want an idea about rebuild kits, then try googling rebuild kits for a gm 350 and see all the different kinds. im not sure about 4.0 rebuild kits, but i would assume there are different levels of kits. you really wont know until you tear it down and measure the tolerances and condition of all the parts.

Yea the engine I'm getting is off a junkyard scrapper, so who knows what could be wrong with it. Looks pretty decent though, was in a front end colision but the belts and pulleys weren't touched so it's hard to imagine the accident affected the engine at all.

Above and beyond the normal expenses of rebuilding a motor, a stroker can be done for about $200 more. I built my stroker about 8 years ago and have over 60k on it. I get 21mpg and it runs very strong. A correctly built and broken in stroker will last as long as a stock engine.

You simply order a different set of pistons, snag a crank and rods from a 4.2L ($100 around here), deck the block. Depending on where you live, you might want to upgrade your injectors, but it is not always necessary. Normally in a rebuild, you replace the cam anyway. There are several good cams that will work for not much more than a stock cam from NAPA.

If you want my recipe or guidance, PM me. I've been building motors for over 40 years.

PS. NEVER KNURL THE VALVE GUIDES, NO MATTER WHAT ANYBODY TELLS YOU. ALWAYS SLEEVE THEM.

Yea you're not the only one that's suggested against that lol

So I'm becoming more and more interested in the stroker idea... is that all there is to it, or am I going to need a new oil pump, water pump, beefier starter for the pistons? If this is really gonna happen I want to make sure to do EVERYTHING right.

old_man said:

PS. NEVER KNURL THE VALVE GUIDES, NO MATTER WHAT ANYBODY TELLS YOU. ALWAYS SLEEVE THEM.

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Just curious what this leads to? Higher oil consumption? Exhaust blowing by stems?

winterbeater said:

Just curious what this leads to? Higher oil consumption? Exhaust blowing by stems?

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Probably can't get precise valve guide dimensions along the length of the hole and it wears out faster but just guessing.

I noticed the rods on mine were pretty rough along the beam where the forging flash stuck out, polish that down & shotpeen them.

Balance the rods & pistons.

Scroll down this page to the tool that cuts a groove in the lifter bore for additional oil to flow to the cam. Try it out & let us know how it goes. If I rebuild another I'll do this.

stroker all the way. Rebuilding the 4.0 is cake. Easiest rebuild I have done, especially if you chose to use new components with matched bearings. My stroker rebuild cost me $1600 running start to finish. I did the following top to bottom:

-Port/Polish head/ reseat springs and shim back to factory specs
-2000 intake manifold and bored TB (I did the TB by myself on a lathe)
-LT1 injectors from a camaro vice a mustang
-new lifters and pushrods
-re-use the 1991 cam, the stock grind there was good enough and since it came out of a 50k mi rebuild anyway it was durn near perfect condition
-new cam bearings
-new timing set
-new water pump
-Heatbuster, all metal radiator, 3 core from advance
-junkyard block (1992) magnafluxed and pressure tested
-pistons from the machine shop (Badger brand aluminum, said they use them in most of their rebuilds with zero problems)
-complete new gaskets, premium ones for the head, valvecover, and oil pan.
-set of reman 258ci rods that had been shot peened and de-stressed
-Reman crank with matching bearings from advance auto
-had the block cleaned, bored and honed
-new high flow oil pump
-new oil pan (old one had several "I" beam shaped holes from where the rod punched through a couple of times)
-Mustang GT holley performance fuel pump. Supports 300hp at 250lph
-there are some random small parts in there too, think I replaced a few hoses and the belt. New stainless fasteners, ect.

I think the $1600 might not include the radiator and fuel pump, but those two probably only knocked it up to about $1800. Don't half ass a rebuild, either you are doing one or not. Since you have to take it apart anyway, do it right this time. The only thing I think I am going to add to all of this, is some kind of nasty cam, and I am gonna advance time it a few degrees. This truck is no longer my DD so I can go a bit wilder on the cam.

i would just do a mild clean up/rebuild on the head. You'll probally have to bore the block .30 over to square it up. which will require new pistons/rings obviously. You may need to turn the crank .10 get new lifters since the OE jeep lifters have a history of failure.all new clevite bearings. Melling O/P,99+ intake manifold,ported TB,Crane cam (up to you) then just all your gaskets. Should be as reliable as stock.

98 jeepjeep said:

i would just do a mild clean up/rebuild on the head. You'll probally have to bore the block .30 over to square it up. which will require new pistons/rings obviously. You may need to turn the crank .10 get new lifters since the OE jeep lifters have a history of failure.all new clevite bearings. Melling O/P,99+ intake manifold,ported TB,Crane cam (up to you) then just all your gaskets. Should be as reliable as stock.

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right, but if you are going to go to the trouble of a complete teardown and replace everything he night as well spend the extra $200 or so to get the stroker. Especially if he decides to bore it over anyway. The only reason I would not do one is if he were just redoing all the gaskets and not planning on pulling the bottom end.

it has been my past experiance that stroker motors tend to consume oil Due to the increased time the piston spends at TDC is this correct?

What about milling the head deck parallel to the crank and cc'ing the heads to get the compression on all cylinders equal? Most factory machings could use this improvement.

98 jeepjeep said:

it has been my past experiance that stroker motors tend to consume oil Due to the increased time the piston spends at TDC is this correct?

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mine does not consume any oil. Neither do the 3 other builds that I know of from personal experience. Actually that Is the first I have heard that or the reason. A friends leaked all the time, but that is because he kept screwing up the rear main trying to install it.

maybe its just some aftermarket stroker pistons...i have seen some with the rings over the wrist pin hole on the piston.....thats why i always tried to stay away from them.

it uses a stock style XJ piston. The ones I used were only different in size other than that they were the same. It may be that you knew a few people who lined all the rings up with the Gaps in a row. I dunno, built right there is no tolerance difference in the motor over stock, built very well there is an improvement.