Extreme Budget Engine Rebuild - Comments Needed

[terrawombat]

I'm trying to do this cheap, really cheap. MY '88MJ Pioneer is in line for a new engine. A shame since the one that is currently in it only has 78K miles, but it was well beaten on and now has low oil pressure and an overheating issue. I currently have a stripped down '01XJ 4.0L block that is in good condition and a complete '00TJ 4.0L block that I suspect has low compression on cylinder #4, not to mention also has physical damage to the motor mount attachment points. In my research of the two blocks, I have found there are too many differences in the blocks to convince me to use the TJ block in my MJ, so here is what I propose:

 

Remove the entire rotating assembly from the TJ block - crank, pistons, rods, rings, bearings, oil pump - and transplant it into the bare XJ block.

 

A couple of things I would do are:

 

1) Hone each cylinder to break the glaze

2) Plastigauge all rod and main bearings to verify that clearances are within spec. If not, replace bearings as needed

3) Inspect oil pump and replace if needed

4) Inspect piston ring endgaps to verify they are within spec. Replace as needed.

5) Find the right cylinder head from a JY or inspect the one on the current engine, although I feel it's trashed.

 

Here are my thoughts. It's not an ideal situation, but the entire rotating assembly in the TJ block should be balanced from the factory so transplanting it into another block shouldn't cause too many odd vibration/balancing issues. I know a lot of people are going to say, 'while you're in there, might as well replace the main & rod bearings and the oil pump and the piston rings.' Okay - but now we're talking a couple hundred dollars in parts...might as well find a low mileage used XJ engine at that point. I don't like the idea of reusing the piston rings, but if they're on a freshly honed cylinder wall and the end gaps are within spec, they should work fine and once they work themselves into the walls, I shouldn't be burning much oil. Shouldn't...

 

Please, I'd like to hear your thoughts on this very budget-minded idea...

[terrawombat]

A quick aside: The first person I proposed this idea to was the machinist at the shop I always use for engine stuff. His response was a very sarcastic, 'I'd like to see that when it's finished.'

[dasbulliwagen]

A machinist would respond like that because he is used to absolute precision. When it isnt absolute he has no other way to respond. But that being said, I have heard of and seen worse things work without a problem. You sound like you know what youre doing, and you have a goal to keep budget as low as possible. I'm sure that if youre smart about it and clean working that it should work out fine, and if it doesnt, then youre out nothing but your own labor, and you can start over. If thats what you have to work with, then go for it! I wish you nothing but luck.... youll be fine!

[terrawombat]

Thanks for the words of encouragement. This isn't my first rodeo in regards to rebuilding an engine, but is certainly the first time I've tried something like this...

 

Low budget is an absolute must for this project. I bought the TJ engine on the cheap for around $140 because of the busted mounting tabs. I felt it was worth it because I was getting a coilpack, '99+ style intake and various sensors I could use on my '01XJ. Of course, the coilpack broke when they loaded it on my truck, but anyway... I should have every part that I need to complete the job sans a few gaskets. Even have a brand new RMS, head gasket, valve cover gasket, and oil pan gasket that have been sitting on my shelf asking to be used so I can even reseal this engine up pretty good.

 

One other thing I'm concerned with is that the original flywheel that came with the TJ engine was a little bent so I tossed it. I'll have to use the flywheel from the XJ engine, which wasn't part of the original rotating assembly on the TJ engine...still should be okay, I hope...

[1987Comanche]

I'd probably go for a new high vol oil pump. They are a known weak link on these engines. True it's $$ but it will correct a deficiency.

[terrawombat]

The stock oil pump is a weak link? That's the first time I've heard that (not being pompous, just honest). My understanding for the purpose of a high volume oil pump is for vehicles that spend a majority of their time off-road, in low gear, at low RPMs so that the engine will have a higher volume of oil while it is being taxed at low speeds. The MJ that this engine is going into will see paved roads 95% of the time.

[1987Comanche]

I'm going from memory here but I believe the life span of the OE pump is usually somewhere around 100K. It will go farther than that but starts loosing ground. The high vol pump has a thicker casting and better gears. A HV pump can increase oil pressure if the engine is in good shape to start with (my Beretta is a perfect example of this...40PSI to 60PSI). Worst case is the excess vol is bypassed back to the pan.

Depending on how long you expect to run the engine an OE replacement pump may be sufficient.

[manche75]

Deffinitally get new rings. I can't imagine they are that expensive, seeing as how chrome-molly rings (the best type out there) for my 351c only cost like thirty somthing. And it has two more cylinders.

[jimoshel]

For a budget rebuild, your on the right track. I've done worse. I once disassembled and reassembled a 1956 1200 Volkswagon using all the old parts, gaskets, rings, bearings etc. It was in Spain. I tore it apart Sat morning and needed it Sunday night. No parts stores, nothing. I broke the no 1 compression ring to the no 3 cylinder and swapped it with the no2 ring. I drove it for 11 months putting 15,000 miles on it like that. Took a qt of oil every 500miles. Finally traded it in on a new '59 Jaguar. Good luck, Jim

[jpnjim]

Every 4.0L I've stripped down has needed rod bearings (copper showing).

Maybe I just hit a string of bad ones, but that includes an 80,000 ish 4.0L that I was expecting much less wear from.

 

As far as balance goes, you should be fine (assuming pistons go back in order).

 

Are you building this into a 91-95 style HO, or are you gonna stay Renix?

 

You were talking about using the horseshoe intake, so I guess you're gonna build an HO to work with your Renix stuff?

 

Out of everything you're reusing, I'd concern myself with the rings & bearings most.

The rings, because if you're going to the trouble of doing the HO upgrade for 10-25HP (assuming horse shoe intake), but risk losing more than that to bad ring seal.

 

The rod bearings because of what I've found in my 4.0L's,

and the main bearings because you're swapping them into a new/different block (probably be OK, but would still be a new variable).

 

The last things I'd wonder/worry about are:

how are the cam bearings in the '01 XJ block (since those would be staying),

and how is the cam in the 00' TJ engine?

 

Of course keep the lifters in order (I know you probably know that, but it can't be said enough).

 

Oh, and I would replace the timing chain, even if I was gonna re-use the old oil. :yes:

[terrawombat]

You lost me at rod bearings... :D

 

I'll cover a few items that I wasn't clear about. I'm going to leave the system as a Renix and will NOT be using the horseshoe intake for this - I'm saving that for my XJ to MJ swap. The TJ engine has a confirmed 83K miles on it, which is low for a 4.0L, but like you said, it can still have significant wear. Obviously, if the bearings on the TJ engine look trashed, then I need to reconsider my options. The XJ engine has 154K confirmed miles and originally came out of my '01 and it had spun a rod bearing, but if you couldn't hear the obvious clanking in the engine bay, you'd never know as it ran fine and, most surprising to me, the oil pressure was absolutely 100% normal. I've seen plenty of spun rod engines in the past (This is very common with the 3000GT/Stealth V6 3.0L DOHC engines) and they all had extremely low oil pressure. This doesn't really have anything to do with my situation at hand, I'm just throwing in some love for the 4.0L engine :D

 

On to the camshaft. I have not inspected either cam. I also do not intend on checking or replacing the camshaft bearings. I don't have the proper equipment to change cam bearings out nor do I want to spend any money on them. In my engine rebuilding experience, unless there was a total oil pump failure, camshaft bearings hold up well over time. It makes sense as there is little thrust on the cam bearings as opposed to the rod bearings which are constantly getting hammered. My plan for the camshaft is to leave the XJ one in the engine with the original camshaft bearings. They've been together for 154K miles and saw good oil pressure even after a spun rod bearing so I'm not going to upset their 'chemistry.' :D

 

Unfortunately, three of the lifters on the XJ engine fell out when I was getting it up on the engine stand. I do not know the order in which they fell out from so I'm just going to have to guess...

 

Remember, this whole idea is contingent on the fact that the rod and main bearings are in good shape. If they're not, I'm looking at $61 for the mains, $30 for the rods, and $92 for the rings (prices are from RockAuto) for a total of $183 plus shipping...yuck. I hate spending that much money on an engine that I know I'm not really putting together the "right" way.

[kastein]

I can get a whole XJ with a running engine, rotted out, for 2-300 around here, with some patience. With no patience, 4-500.

 

I would not do a rebuild right now... pick one up, part it out, sell each axle for 100 bucks, seats for 25, etc and you are already ahead. Pull all the senders, harnesses, ECU etc that you can use on yours and keep them. Then sell the carcass to the scrapper for another 1-200 and you basically have a free motor, tranny, and transfer case.

[terrawombat]

Believe me, I would LOVE a parts XJ. I can almost justify getting one for all of the nuts, bolts, screws, and other miscellaneous hardware I could steal from it so I can keep my MJs as close to factory as possible.

 

HOWEVER, I need to be realistic. I currently own six cars - 5 Jeeps and a Mitsubishi - and two motorcycles. I'm extremely fortunate that my father is the person that is he and has literally given me an old barn to call my 'shop.' Even though I DO have the room, I don't know if I can bring another vehicle into the fleet. I'm not going to live where I live forever and I may be moving as early as the summer of next year and it's a 99.9% shot that my new home will not have a 5,000 sq. ft. barn to store stuff in. I need to start getting RID of my assets rather than continue to collect them.

 

One of the other ulterior motives of this budget engine rebuild is so that I can transfer the good parts from this otherwise busted TJ block into a good block and maybe make something out of nothing. Once I finish the transferal of parts, I'm going to take the TJ block and XJ crank to the scrapyard.

[Squeegy410]

Deffinitally get new rings. I can't imagine they are that expensive, seeing as how chrome-molly rings (the best type out there) for my 351c only cost like thirty somthing. And it has two more cylinders.

 

ive got a 351c sitting out back that I'm dying to rebuild but need to build my truck first to have something to put it in :ack:

[terrawombat]

One other thing I'm concerned with is that the original flywheel that came with the TJ engine was a little bent so I tossed it. I'll have to use the flywheel from the XJ engine, which wasn't part of the original rotating assembly on the TJ engine...still should be okay, I hope...

 

Tonight I realized that this isn't going to work. I'll need to use the flywheel that's in the MJ right now since (I believe) the Renix CPS needs that flywheel to work properly.

[Rampage]

Check the bearings. If they are okay (no copper showing, as mentioned) keep going with them. Replace the piston rings and headgasket, possibly the intake manifold gasket if it doesn't come off in one piece.

 

I did a budget build like this on my 89 Civic.... rings and a headgasket, and some incidentals, cost less that $150.

 

Cheers,

Mark

[kastein]

yep... all OBD (I and II) flywheels/flexplates are compatible afaik, they definitely are if you put a newer one into an older vehicle just not sure about the other way around. RENIX vs OBD is very very different however.

[terrawombat]

After doing some research and talking with some 'old time' engine rebuilders, I think I'm going to splurge and get new rings.

 

What is incredibly confusing is how the auto parts stores are listing the rings for each engine. Apparently there is only one set of rings I can get for an '01 XJ engine - Sealed Power Part #E925K. But if I look up ring sets for the '00 TJ Engine, I get a variety of rings to purchase, including the Sealed Power rings I just mentioned. So, what I gather from this is that I can use TJ rings in either engine, but XJ rings are specific to XJ engines only? What also doesn't make sense are the ring thicknesses they list on the parts sites. Some sets are in Imperial units while others are in Metric, but they are not equal? Both sizes, regardless of what unit of measurement they're in, do not fall within the Specification ranges in the factory service manual.

 

Doesn't make much sense at all, so I'll have to do some of my own measuring once I pull this all apart.

[manche75]

See if your local machine shop sells the rings. They usually get them cheaper than stores like Autozone, and generally tend to pass the savings on to you. Plus, they will probably set you up with the correct set.

[terrawombat]

I went with a set of Sealed Power rings from Advance Auto for $37.99 plus I had a list of other things I needed to get for the rest of my fleet and they have a 40% off coupon when you spend $100 bucks so I used that. Rings came out to $22.79 plus tax (shipping was free since I spent over $75).

 

So we're about $23 into this build...hope to keep it under $30! I'm going to be borrowing a hone, ring expander, and ring compressor from a guy I work with.

 

Crossing my fingers that the bearings are good!

[jpnjim]

I'd also cross my fingers that the three lifters end up in the right holes.

 

Lots of people are having problems wiping out cams,

swapping lifters from one hole to the next on a used cam is almost a sure fire way to wipe out a lobe.

 

You could treat this build like you were breaking in a new cam (lots of cam lube on those 3, and keep the RPM's between 2000 to 3000 rpm for the first 20 minutes you start it),

but I'd think about just swapping in the TJ cam if you know exactly which lifter goes with which lobe for that cam.

 

Even better would be a used cam (with matching lifters) from an 87-95 4.0L, since that was a bigger cam anyway (they downsized the 4.0L's cam in 1996).

 

Either way, good luck. :cheers: