4.0L HO Jeep Engine Build

[ramcharger]

Sorry this is late folks but the day I asked Rumble where I should post this I got some real bad news. Anyway, it's time to get started and offer some help to those who have a Jeep (Hey, it's a Mopar too!). Normally I'd be giving the dogs a their 2 mile walk right now but it's snowing and I'm just getting over a fever so I figure that wouldn't be a wise choice. They get to run around the back yard this morning and get a nice warm towel off when they get done. :-D

I'll start from the beggining here and let you all know how this started:

I bought a '92 Jeep Cherokee Limited with 210K mi. in December of 2008 from money I received after my 4Runner got totalled in front of my house (damn drunk drivers). I got it for $900 bucks, everything worked except the air conditioning and power front drivers seat. It had a "tick" from the valve cover and I thought for sure it was a collapsed lifter as it would come and go, but it hads what I thought was great power compared to the Toy and had room for the dogs.

I drove it for about a year or so and realized that the mileage was pretty poor and I was getting tons of blow-by. So much blow-by that the PCV system was getting clogged and the air filter was getting soaked with oil. Oil consumption was about a 1 qt. every 500 miles or so too. I decided to just pull the engine and a do a re-ring as well as change out all the lifters and replace the rear seal too as these always leak on these 4.0's.

Well, this is what I found once I tore it down. Two pistons were destroyed and the factory header was cracked. I'm stunned that it ran as well as it did. I can only make an educated guess as to what caused this. Most certainly it was detonation but what caused the detonation? Well, the Jeep has a giant class IV hitch with the large round trailer connector and it was originally from Lousiana, so I'm thinking that someone was towing a really big boat and trailer with this thing and running crappy gas to boot. This engine had a hard life and for it to keep running this long is amazing anyway.

 

[ramcharger]

The '92 block took the damage pretty well considering the pounding it took for thousands and thousands of miles. After mic'ng it out, I figured it would take a .040 bore to clean up. I contacted a couple local dealers and they wanted $250+ per piston, so that was out of the question. I did some research and found that Speed-Pro offers a coated replacement piston set including pins for a very reasonable price (about $150) but they were on back order for the .040" oversize.

At this point I figured I'd see if I could find a good shortblock on Craigslist that just needed a hone to save money. I decided on a '99 or later block for a few reasons:

1. They have a stud girdle to reduce NVH and are considered a stronger block.
2. They use pistons with a the thinner metric ring pack which should reduce friction.
3. If I'm lucky, the seller will give the intake manifold with the block (I'll get into this later, but the later intake is a much better piece).
4. Newer block, less mileage (I hoped).

Well, the later block I picked up for $200 had problems too. The rings were again seized on the pistons!?! Dam it! On the good side, the guy gave me two 99+ intake manifolds, two sets of injectors, one good alternator, two sets of exhaust manifolds, a late coil pack and the head and crank were in excellent condition so all in all I did OK.

On this late block, one of the timing cover bolts had worked it out and covered the block with a nasty, thick layer of mixed oil, gravel and road grime. It was so bad that I didn't even want to risk mocking it up so off to my machinist it went for a baking, cleaning and boring. The bore on this block only needed a commonly availible .030 over piston set and as mentioned before, uses the thinner metric ring pack. The first picture shows all the road grime and the second shows the girdle that comes standard on the later block.

 

[ramcharger]

Now on to my goals for this engine. It will be for a daily driver so mileage and useable power are top on the list. It won't be a high rpm screamer, nor will it be turbo'd or supercharged. I just want the most power I can get for the lowest price with the least mileage penalty. I know that these engines can be stroked to 4.5L, 4.6L or even 4.7L fairly easily, but that is out of the scope of this build. Maybe later as I still have the early block.

Here's the mods as planned:

1. .030 overbore, always worth a couple of ponys.
2. Later block with thinner ring pack coated piston, less friction.
3. Decking the block for .040" quench, more compression and less chance of detonation. Compression is always worth power, as is quench.
4. Set my bearing clearances to .0025, less friction.
5. Using the early ('92) head. It has larger ports than the late head and also did some home porting and had my machinist bring the valve seat out to very outer diameter of the intake valve but the left the ex valve pretty much in the middle to maintain longevity.
6. I'll be using the late intake manifold. Much better design. It was originally engineered to to pick the HP back up after using the smaller port head and cam on the later models to reduce emissions.
7. I'll be using the early throttle body (it's bigger than the late model).
8. Swapping out to mustang style 24 lb injectors. They are the 4 hole disc type and should give better atomization.
9. Aftermarket SS header. It give better flow and solve the cracking issue that plagues the 4.0L HO.
10. Cat back exhaust. Less flow restriction.
11. Early style ('92) cam, more lift and duration than the late model cam.
12. New, high flow cat.

Pic 1, the new header. It was cheap. There are better headers than this but they are very expensive. This header was less than $150 shipped.

Pic 2 Here you can see the difference from the old vs. new style intake.

Pic 3&4 Nice shiny new pistons. They give me a nice warm fuzzy feeling deep in my heart. These rods are press fit so this was done at my machinists place. Note the very narrow ring grooves.

 

[ramcharger]

Here's the block when I got it back from the machinist. As usual, he did an exceptional job. He took .007 off the deck (as requested) to straighten it out too.

 

[ramcharger]

Time for some paint. Rustoleum is now making engine paint so I thought I'd give it a try. First I got off the loose stuff, wetted it down with paint prep, masked it off, shot it primer than a couple coats of black (the original color). I have to say that I'm super impressed with the Rustoleum engine paint! Great stuff and covers very, very well. The industrial gray primer looked really kind of good too. Hmmm.... Too bad I'm not rebuilding a generator or tractor.

 

[nothingbutdarts]

Awesome Joe,

Keep the info. coming as you progress!

 

[ramcharger]

At this point, I did the mock up to check piston to deck clearance, ring gap, rod side clearance, triple check bearing clearances, set the thrust bearing and check crank axial play. This is when I usually find any unexpected problems and sure enough, the pistons were still .033" below the deck but everything else was spot on.

Here's the deal, if I have another .033" taken off the deck, I will certainly have too much pre-load on the lifters as the head will be brought .033" closer to the cam centerline. These rockers are not adjustable from the factory, so I have 3 options:

1. Blow it off, assemble it as is and not have any quench.
2. Have it decked the additional .030 and purchase an ajdustable rocker arm set (big, big bucks).
3. Have it decked, mock up the head and have some custom pushrods made.

I'm opting for option 3. There may even be the right length for this custom application for another app like a chevy. It's just a ball-ball style pushrod so we'll see. I still have to break it down and get it back to Dave Capriotti. He said he'd only charge me half what he originally charged me for the decking! He's a decent guy and the work they do there is exceptional.

 

['64 Cuda]

Is that stud girdle as light as it looks? I have a 1983 4.2 with 4.0 head & EFI. Could I just stick a factory stud girdle into my block or is there a difference in the main caps or something else that would be a problem?

 

[BrianT]

Good job so far!! I have a 91 4.0 in the boy's Cherokee that has a slight knock in it, so I'll be following your progress closely!!

 

[ramcharger]

Awesome Joe,

Keep the info. coming as you progress!

Thanks Kim! Here's some more.

I had DC Racing do the valve job too and here's how they returned my parts. Note how the valve seat has been moved up and out and how they back cut the valves for me. These guys are the best!!! :-D I used to do my own valve jobs back in the day with Neeway seat cutters and tabletop valve grinder but I no longer have access to these machines and tools. Thank Goodness I found someone I could trust here in Colorado. Again, notice how the seat was brought out to the outer diameter of the intake but kept closer to the middle on the exhausts for longevity.

 

[ramcharger]

Is that stud girdle as light as it looks? I have a 1983 4.2 with 4.0 head & EFI. Could I just stick a factory stud girdle into my block or is there a difference in the main caps or something else that would be a problem?

That girdle is actually pretty darn stout. IIRC, it's over a 1/4" thick and has quite a bit of heft.

If I were you, I'd take that 4.2 crank and drop it in a late block (they're a dime a dozen at the bone yard) and make yourself a 4.6 stroker. The main cap bolts for the girdle are different and do interchange among the 4.0's but I don't know about the 4.2's. Oil pan clearancing my be necessary too.

Good job so far!! I have a 91 4.0 in the boy's Cherokee that has a slight knock in it, so I'll be following your progress closely!!

Glad I could help someone here, that's the idea. 8)

 

[ramcharger]

Here's the head as received from DC racing prior to porting. This is really a nicely designed head with a generous quench pad and very large valves for it's displacement. No wonder the factory was able to squeeze 190 HP out of these right from the factory with no special treatment or hand assembly. :read2: DCR also took .006 off the head deck to straighten it out as well.

 

[ramcharger]

Here I started to do some porting. Don't jump on me! It's not done, lol. The ports are just roughed in at this point. Note the cutout at the upper corners of the intake ports, that's where the injector sprays in from the intake manifold. Also note the serious core shift. I took a lot of meat out and the parting line is still there. I concentrated my efforts on the port roof and when doing home porting I try to "Be the air/fuel molecule" and imagine where I would want to go and pretty much stay away from the port floor. I don't have a flow bench so I do my best. If I were totally serious about this, I'd have DC do it for me.

 

[memike]

I have owned 3 4.0 in line 6 jeeps and all the mud and rock climbing folk here in Arkansas swear by them :cheers: And it is amazing the the mileage that can be put on them, our mail carriers drive these in line sixes 8 out of ten 8) If a Jeep finds it's way back in my life before a Ramcharger I am shopping for the in line 4.0 is a must have.:read2:
It's great to see another helpful thread you have started Joe :cheers:
The snow is gone here know But it is wet and nasty outside I am glad I live on a hill and rookie ground :-D I can't wait to see how much energy this build will make :cheers:

Glad to here you are at normal running temperature Joe :happy10:

 

['64 Cuda]

That girdle is actually pretty darn stout. IIRC, it's over a 1/4" thick and has quite a bit of heft.

If I were you, I'd take that 4.2 crank and drop it in a late block (they're a dime a dozen at the bone yard) and make yourself a 4.6 stroker. The main cap bolts for the girdle are different and do interchange among the 4.0's but I don't know about the 4.2's. Oil pan clearancing my be necessary too.



Glad I could help someone here, that's the idea. 8)

I was more interested just for the sake of knowing. I guess it's just that the girdle doesn't look like much compared to the one I bought to use in my 408. My completely rebuilt 4.2 has been finished for at least a couple of years & sitting on the engine stand while I keep nursing along the car with the engine it has now. Still need to iron out a few things to make the EFI work in my '86 car. Meanwhile, the other mechanicals on the car have me busy just trying to keep the thing on the road. :-D

 

[ramcharger]

I have owned 3 4.0 in line 6 jeeps and all the mud and rock climbing folk here in Arkansas swear by them :cheers: And it is amazing the the mileage that can be put on them, our mail carriers drive these in line sixes 8 out of ten 8) If a Jeep finds it's way back in my life before a Ramcharger I am shopping for the in line 4.0 is a must have.:read2:
It's great to see another helpful thread you have started Joe :cheers:
The snow is gone here know But it is wet and nasty outside I am glad I live on a hill and rookie ground :-D I can't wait to see how much energy this build will make :cheers:

Glad to here you are at normal running temperature Joe :happy10:

My head still feels congested but I'm feeling much better now. Like you say, these really are great engines and worthy of a decent rebuild Mike. I'm hoping for an honest, reliable 200+ hp out of this build.

I was more interested just for the sake of knowing. I guess it's just that the girdle doesn't look like much compared to the one I bought to use in my 408. My completely rebuilt 4.2 has been finished for at least a couple of years & sitting on the engine stand while I keep nursing along the car with the engine it has now. Still need to iron out a few things to make the EFI work in my '86 car. Meanwhile, the other mechanicals on the car have me busy just trying to keep the thing on the road. :-D

No, it's not as stout as the girdle you would see from Hughes Engines for a LA/Magnum engine for example, but it is a factory piece. Then again, it won't be a 500hp monster either and for a free upgrade, I figured I'd take it. :-D I believe the engineers designed it more to reduce NVH than to add strength as there were no previous problems with main caps or webs breaking or cracking. Since this is a really long engine, I'm thinking more of a torsoninal rigidity issue and that it may reduce those vibrations rather than eliminate cap walk/rock like a V-8 girdle should do. Note that it only ties the caps together along the length of the engine rather than tie the caps to the block and each other like a V-8 girdle does.

OK, this is as far as I've gone so no more until get the block back to DCR or finish up the porting.

 

[fishy68]

Looking good Joe. That head does look like a real good design. No wonder they ran so good. My Dad bought a new 89 Jeep Cherokee with the HO engine and 5 spd. and it ran real good and lasted a long time. Great little engines.

 

[Fishy]

Really makes me miss my '93 ZJ. I wanted to punch mine out to a 4.6, but sadly I beat the crap outta the thing before I could get that far. LOL

 

[ramcharger]

Looking good Joe. That head does look like a real good design. No wonder they ran so good. My Dad bought a new 89 Jeep Cherokee with the HO engine and 5 spd. and it ran real good and lasted a long time. Great little engines.

I was pretty suprised at the engineering they did on the head. Mopar strikes again!

Really makes me miss my '93 ZJ. I wanted to punch mine out to a 4.6, but sadly I beat the crap outta the thing before I could get that far. LOL

Most Jeeps get beat to death. :-D

Well, I finally got the block back to machinist today and got a few pics of his shop with his permission. That engine in the dyno room makes 640 hp with a 390 cfm carb.

 

[fishy68]

Nice shop!

 

[ramcharger]

Nice shop!

I've seen dentists offices that were not as clean as this machine shop. I didn't get pics of the engine assembly room and the head assembly room, they were antiseptic.... One of the guy's there showed me a Kaase head he was assembling for a Ford drag car. The head used triple springs with 300+ lbs. on the seat and 900lbs open!!!! It was expected to make 1500 hp to the wheels and spin at 9000+ rpm.

Seeing his shop has motivated me to clean my garage, lol. I wanted to get the block out before I swept and vacuumed anyway. I plan on finishing the porting today, we'll see how that goes.

 

[CudaChick1968]

Making good progress Joe! Keep us posted.

I think your engine guy needs a new redhead renter. LOL @ all those cool goodies to play with!!

 

[nothingbutdarts]

Hay Joe,

You need to add this to your build, it looks sweet!

http://denver.craigslist.org/pts/1673140595.html

 

[ramcharger]

Making good progress Joe! Keep us posted.

I think your engine guy needs a new redhead renter. LOL @ all those cool goodies to play with!!

Oh man, could I have fun in there....

Hay Joe,

You need to add this to your build, it looks sweet!

http://denver.craigslist.org/pts/1673140595.html

Too bad it's 2000 not 200...:-D That would bolt right on too and be just the ticket for being here in the "rare air". :cheers:

Porting is done. Pictures are coming up as soon as I get all the dang iron fillings cleaned up. Porting iron heads is a mess.

 

[nothingbutdarts]

Porting is done. Pictures are coming up as soon as I get all the dang iron fillings cleaned up. Porting iron heads is a mess.

Great on the lungs too!