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5.2L Rebuild advice?

7K views 49 replies 9 participants last post by  Spetie 
#1 ·
Hey fellow Jeepers! I've started an engine rebuild and transmission+t-case swap in my 95 ZJ. I'm going with a factory auto trans and I got an NP231 D out of a Dakota. Anyways, my real question here is what all can I or should I do while I have everything torn apart. Mainly concerned about the engine rebuild. I'm a competent mechanic and I'm not worried about getting the job done I just want a few pointers or things I should upgrade/fix/remove while I'm here. My 5.2 has about 250k on the dash so she's ready for some love. Anything you guys think of that might make my life easier now or in the future would be awesome. Thanks in advance!
 
#2 ·
Intake plenum pan is always a good upgrade to do while everything is accessible. Check cylinder heads for cracking and replace as necessary. That said, I'd rather spend my money building a 5.9 than a 5.2 if you can swing it.
 
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#3 ·
Another vote for just dropping a 5.9 block in.

I’d probably assume the heads want to be replaced, magnum heads are almost always cracked, even if it isn’t causing an issue yet. There are good aftermarket options for stock like iron or aluminum heads.

Plenum pan is a good plan, but an aftermarket intake is preferable if you want to make extra ponies.
 
#4 ·
All the standard stuff.

New timing chain + gears. Disassemble and clean oil pump pickup tube, don't forget to prime the pump. Remove / replace all freeze plugs, I scraped clean everything possible on the block and heads cooling passages interior, I used brass freeze plugs for better sealing. Many lifters on mine collapsed, I was able to restore normal operation by disassembling all followed by severe cleaning then reassembly.

The FSM does not specify thread locker on the flex plate bolts, to the crankshaft and to the torque converter. Thread locker is required.

Use ONLY OEM sensors for oil pressure and CPS. Remove both before removing engine.

If remaining w/ OEM plenum pan, chase the blind holes and the bolts, ensure they will hand tighten w/o the pan so that they will properly tighten per the FSM w/ all parts installed, as-shown in this reply. Follow TSB 09-05-00 for installation. Use new plenum bolts, as they stretch to torque.

Make a table showing bolts and studs locations for each rocker cover prior to removal. Thank me now or later for this gem.

The Miller 6635 tool is required for proper timing cover placement.

Implement the TSB 18-48-98 for the spark plug wire routing.

Chances are the original rocker cover grommets have gotten hard. I replaced mine w/ the Mopar 0294 6079 Crankcase Vent Grommet and the Mopar 5303 0017 Crankcase Vent Grommet. They can be a butt pain to replace but the new ones work better than the old.



When I replaced the rear main seal the second time I installed it w/ 30° rotation, so the halves don't meet at the block surface. It leaked the first time, per the FSM. It didn't leak the second time w/ the rotation.

The FSM-specified bolts for oil pan gasket placement are very handy, as-shown in this reply.

This reply has some good info and images.

The dipstick tube is made from unobtainium, so do not damage that part.
 
#5 ·
Well this thread answers one question I had... my local junk yard sells engines for $250 and I had been thinking about picking one up to rebuild and have in storage. Wasn’t sure if I should do the 5.2 or 5.9. Does anyone have a link to threads detailing the 5.2-5.9 swap. I think there is something in the “check here first” threads but I can’t remember if it was very detailed.
 
#7 ·
Well this thread answers one question I had... my local junk yard sells engines for $250 and I had been thinking about picking one up to rebuild and have in storage. Wasn't sure if I should do the 5.2 or 5.9. Does anyone have a link to threads detailing the 5.2-5.9 swap. I think there is something in the "check here first" threads but I can't remember if it was very detailed.
They are extremely similar engines, it's about as easy as swaps get. You need to use the 5.9's harmonic balancer and flexplate as it is externally balanced (the 5.2 is internally balanced) and you'll re-use your 5.2's intake/exhaust manifolds and accessory drive, assuming the 5.9 is from a Dodge. You'll want to buy a driver's side motor mount for a '98 5.9 ZJ as the block mount ears are a bit different for some strange reason, you can re-use your 5.2's passenger side if it's in good shape. If you're on a tight budget and want a few extra ponies for free, put the 5.2's cam in the 5.9.
 
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#6 ·
5.2 and the 5.9 are the same motor except the bore and stroke. You want to have a look inside the motor, I got two motors(for different vehicles) with at least 200k on them and both need a bore due to scratches in the cylinder walls. And the cams where shot also. If you are planning all new parts and bore than don't worry about it. If you want to freshen it up that's another story.
Plenum pan is a good plan, but an aftermarket intake is preferable if you want to make extra ponies.
Aftermarket intake you will loose low end power and gain it in the upper rpm range.
 
#11 ·
"Better"

What's better?

The mechanical specs of the shortblock are pretty much the same for any magnum 5.9. Everything else is shared between the 5.2 and 5.9 in a jeep, or other dodge.

Now the jeep 46re, that's the rare part if you can find one. Way stronger than the 904 based 44re.

My build had an unplanned 5.9 swap: https://www.jeepforum.com/forum/f13/n6mzv-build-thread-kg6mov-1442312/index28.html#post40271707

For your 98 it's drop in the longblock, throw on your intake and accessories and go.
 
#13 ·
if I grab a computer out of a GC5.9 will it work with the 5.9 engine I'd likely grab from a truck?
Your GC is a 95 and is OBD1, As long as you stick to OBD1 it will work. In 96 everything when to OBD2 and is not compatible. It doesn't mean you cant use the engine but transmissions went from the 46RH to the 46RE. If a truck has a manual trans you cant use the pcm you need one for an automatic. Just keep in mind what will work and what won't.
 
#20 ·
With the 5.2 computer you can run regular, I do. I'd keep the current computer and get a tune over swapping pcms.

Tuned you'll want to run premium, and the mpgs tuned will be worth it.

If you can keep your foot out of it . . .
 
#24 ·
I filled up last night at 3.99/gal for regular.

At least the jeep only took 20 gallons, filling both tanks on the f250 takes multiple cards.
 
#25 ·
^—— yikes kg lol

Didn’t want to start a new topic, but I was out at the scrap yard today, taking inventory on the 5.9’s and the question popped in my head. If I am going to get a rebuild kit does it matter how many miles are on the engine already? Would it be a bad move to rebuild an engine if it already has 150k+ miles?
 
#26 ·
^-- yikes kg lol

Didn't want to start a new topic, but I was out at the scrap yard today, taking inventory on the 5.9's and the question popped in my head. If I am going to get a rebuild kit does it matter how many miles are on the engine already? Would it be a bad move to rebuild an engine if it already has 150k+ miles?
No, as a matter of fact a lot of engine builders prefer a high mileage block. The theory is it's been through tons of heat cycles and will be tighter and will expand and contract less after machining than a brand new block. The 5.2 that I rebuilt for my TJ had 250k on it and runs like a champ.
 
#27 ·
It depends on what you mean by rebuild. If you're hoping to take a good running junkyard engine, give it a set of bearings, a light hone, new rings, and call it good, then mileage matters. If you're going to have machine work done (bore and hone, cut the crank, etc.) then it doesn't matter.
 
#28 ·
Sry to keep reviving this thread lol, but iv been doing a lot of research on this the last couple weeks and there is just too many options out there.

At this point we are no longer talking about the 5.2 and I have decided I’m going to do a rebuild on a 5.9. (As if I were the op lol)

I will likely end up starting with something from the salvage yard and the end goal here will be to build the best engine for overall hauling whether it’s a trailer or a camper.

But there is a looot out there, so I could really use some advise on what would be best. I’m not made of gold but I wouldn’t mind dumping some extra money into this if it would assure me of a solid engine that will haul without issues through these Ozark mountains and something I won’t have to worry about for a long time.

Looks like summit racing has several rebuild kits that come with pistons etc. They appear to range from $200-450.

Would it be best to get a scrap yard 5.9 and one of these kits since it’s been sitting in the yard for lord knows how long? Would you take it down to the pistons and everything or just replace the gaskets and move on with your life? Would you also opt for newer/aftermarket heads? If so what would you recommend for heads?

What machine work would you get done, boring honing etc?

I was also thinking of getting new exhaust manifolds at this time too since everything will be out. Any leads/recommendations on those?

Anything else I’m not speaking of that you would do or maybe want to do. OT is a go for me right now and my wife has given me a green light to get the work done so I can get some work done on my Jeep lol.
 
#29 ·
Cheapest way to start is a junkyard motor. Most builds start there, crate engines are expensive. Do a complete teardown and build it right. Have block and heads magnafluxed for cracks before you put any money into them.


Do not buy parts until you have your rebuild candidate in hand and torn down. You can't order pistons until you know what your final bore will be, and you won't know your final bore until you have a bare block and measure the bores. Similar goes for crank bearings - you can't order until you know if your crank needs to be cut or not.


There's no real guideline of "x number of miles = needs a rebore" either, my 5.2 block had just under 400,000km on it and the bores were perfect, no machine work needed if I'd have decided to rebuild it. The 5.9 block I built had half that mileage and needed a bore (although it may have been a tapered bore from the factory rather than due to wear).


Use assembly lube on everything. Follow the FSM. Measure your bearing clearances - use the proper tools if you have them, if not, lots of engine have been built with Plasti-Gauge. Measure you ring gaps properly.


Headers are rare and expensive and require custom exhaust work to fit. Not where I'd spend time or money compared to more important things, like cam/heads.
 
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#30 ·
Cheapest way to start is a junkyard motor. Most builds start there, crate engines are expensive. Do a complete teardown and build it right. Have block and heads magnafluxed for cracks before you put any money into them.

Do not buy parts until you have your rebuild candidate in hand and torn down. You can't order pistons until you know what your final bore will be, and you won't know your final bore until you have a bare block and measure the bores. Similar goes for crank bearings - you can't order until you know if your crank needs to be cut or not.

There's no real guideline of "x number of miles = needs a rebore" either, my 5.2 block had just under 400,000km on it and the bores were perfect, no machine work needed if I'd have decided to rebuild it. The 5.9 block I built had half that mileage and needed a bore (although it may have been a tapered bore from the factory rather than due to wear).

Use assembly lube on everything. Follow the FSM. Measure your bearing clearances - use the proper tools if you have them, if not, lots of engine have been built with Plasti-Gauge. Measure you ring gaps properly.

Headers are rare and expensive and require custom exhaust work to fit. Not where I'd spend time or money compared to more important things, like cam/heads.
Would you recommend grabbing only the engine block from the salvage yard? And buying everything else remaned/new? My yard sells gas engines for $250 I'm assuming this is block + heads not 100%. Engine short blocks for $140.

But if your thinking the money would be best spent elsewhere should I get some aftermarket heads? I'm seeing remaned heads anywhere from $550 for both to 1k per head lol. The 1k per heads are out of the question. But when it comes down too it am I better off getting a higher performance aftermarket head or just going with the salvage yard heads and taking the to the shop as well?

Should I go to a larger bore size? What should I keep an eye out for when it comes to the crank?

Between my brother and I we will likely have any/all tools/gauges needed. So I'm not too concerned there. What about the air intake, are there better options out there or should I stick with the stock one I'll end up pulling from which ever dodge 1500 I decide to pull from?
 
#33 ·
With a use case of towing/longevity and a budget of $1500, I would recommend a basic long-block rebuild with upgrades if budget permits. You will find that a $1500 budget is quickly consumed by machine work (if needed) and the price jump to things like strokers and aftermarket heads will quickly hit the $5000+ mark. It'll run on the stock computer and won't drink a ton of fuel in pursuit of horsepower. The stock intake is also best for that application.

So yeah, basic rebuild with factory parts. If you have the bottom end assembled and find you have a bunch of money left over, start thinking about heads and/or a cam. I wouldn't even put any money into the factory heads until you're absolutely sure you're going to use them.

One thing to keep in mind is that even a minor cam upgrade requires you to upgrade the weak stock valve springs, which is ~$200. Not a ton of money, but every dime you put into them gets you closer to the price of a much better aftermarket head that already comes with good hardware. So even the bare minimum upgrade (cam) quickly starts trending towards a $1500 complete cam+head upgrade and now you need a custom tune too. How it goes with Mopars.

Indy: https://indyheads.com/

Towing a camper at the upper end of the ZJ's rated capacity... I'd probably spend money on brake upgrades before engine upgrades.
 
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#34 ·
Yea I'll be doing the brake upgrade with a few other things as well. This all started due to having some serious engine issues with the current 5.2 in the thing right now. But it's been knocking so hard and bad lately that I'm worried what I'll find when I pull the head to replace the at minimum bad hydrologic lifter. That and iv been want to move to the 5.9 for awhile now.

On that topic anyone know why these rockers are so expensive?

https://www.summitracing.com/parts/csp-s70037/make/dodge

I saw that website however I must have been looking at the wrong spot, but I think it seeing them now.
 
#35 ·
Doesn't seem that expensive for 16 harland sharp rockers.

At your budget point the best thing is gonna be a pretty near stock 5.9 and a proper tune for it.
 
#38 ·
"worth"

If you need 1.7 ratio roller rockers, they're worth every penny. Are they the best $500 you can throw at a stock motor? Uh, no. Stock ratio used to be 1.5 on the la, but the magnums got 1.6, most modded motors stay around there. Harland sharp is one of the few companies making direct fit magnum style rockers.

If you're going to mess with heads I'd go directly to the indy heads as a minimum, and edelbrock aluminum if you can. I believe the edelbrock heads use a more common chevy style rockers, which are more common and therefore cheaper.
 
#39 ·
Oh geeze, well if 1500 budget is only going to get me into a pretty standard 360, what would be the next upper price point? How much are we talking for noticeably more power without jumping into the 5k/stroker territory? I’m thinking if the top of my budget is just going to get me into a standard 5.9 than maybe I’ll just repair what I have (as long as I haven’t run too long with the issues I’m having) and save my scratch for later on down the road. That being said I have had some pretty hard knocking for awhile now.
 
#41 ·
It's a game of time and money.

If you're going to trust a junkyard block, you're probably going to need to take it to a machine shop and have them work it over and check it.

At that point you'll probably be over budget before you get the thing home.

If you're not planning on building motors for fun, getting setup to build motors is expensive. Best thing to do is figure out who you're going to be working with for the build. Figure out what your local options are for machine work and talk to them.
 
#43 ·
Thanks Kg, I'm more of a 1 and done kind of person. I love learning as much of this stuff as I can for what I'm going to do but I doubt this will turn into something I will be wanting to do over and over again.

My other vehicles are an 05' BMW 330i ZHP(DD), and an 2014 Chrysler T&C (for the wife). Neither will I be doing anything close to any of this stuff with. The Bimmer is a huge bi*** to try and work on and my wife loves her T&C. Maybe I'm just chasing an unrealistic dream with doing all this with my ZJ =\ maybe I just need to dump a stock 5.9 have something that does 80% of what I want to do and get something else to do the heavy lifting when it comes to the camper =\ not what I was dreaming of but might be what I'm stuck with.
Realistically the camper we end up getting next year is going to end up being 5k lbs and not sure if I want to be always pulling at the top of my limits in the ZJ
 
#44 ·
Keep in mind that you still have a 44re. It was easy for me to drop a 5.9 in my green pig knowing I had a jeep 46re sitting in the garage.

It's interesting to me, when looking at horsepower numbers, the niner has supposedly the same ponies as my 460 big block in the tow mule. I've done a lot of towing with the 5.2 ZJ's, both the green pig and our 98, and the difference isn't the hp or even torque compared to the truck. It's gearing and setup.

I think you'll be really happy with a stock like 5.9 and a tune, I'd lean toward buying crate so you get something that you know is ready to run.

The thing that's going to determine success with the trailer is gonna be gears, transmission, and cooling.
 
#45 ·
Right on, once I get this engine issues taken care of I'll go ahead and put my 2.5 lift on I have OME springs and Bilstein shocks on and my 16in snowflakes. Tires will be 245/75/16's. Iv got so much bought and ready to go in but just worried about adding any more strain until
I get the engine back to good standing. Regearing and the brake upgrade will be next. I can't remember the best gear ratio but I want to say that I remember reading that the JK stock gears fit perfectly for the ZJ's as well.

I have been wondering if the transmission would be a better investment when it comes to
hauling.
 
#46 ·
Aftermarket heads: Indy MA-X heads are IMO best bang for your buck. $995/pair assembled according to their site but you'll need to verify pricing.
There are not much in the way of intakes for Magnum motors sadly.
If you are going to change the heads i believe both the indy and EQ heads you can get them with the LA style bolt pattern. This opens up a world of different intakes you can use. Although i have heard the EQ's have had some issues with them lately.

http://www.magnumswap.com/using-la-parts-on-a-magnum/

https://www.allpar.com/mopar/performance/manifolds.html
 
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