Replacing Engine

[KMAPRO]

OK, I have decided that I need to go ahead and replace the engine in my 87 MJ. It has the 4.0 in it now and I plan to go back with another 4.0.

 

I need to do this now because my other truck (01 Dodge Ram 1500) now has a blown motor. Seeing as this is my only other mode of transportation (a side from my wife's Suburban), I need to get the oil leak stopped and the number 2 cylinder repaired.

 

My plan is to find a motor from a salvage yard or similar venue. I basically just plan on bolting it straight up and not going through it. I will take my current engine and go through it for a total rebuild.

 

I am not a mechanic, so I am asking y'all what you would do to the new engine before it goes in? I know the standard fluid change and spark plug change, but what else would you do to it before you bolted it in.

 

Keep in mind that I am only looking to use the new engine until I get my Dodge motor replaced and my old 4.0 rebuilt. All I need is a reliable running engine that I don't have to put a quart of oil in every other day and will last me about 6 months or so.

 

I am hoping that I can perform the motor swap in just a weekend.

 

Thanks in advance

 

**EDIT**

 

What all year model engines will directly bolt in my Jeep? I think I heard 86 - 91 4.0, but I am not positive. What all models can I pull from? MJ, XJ, etc...

[Eagle]

Your '87 has the Renix injection/ignition system. Direct replacements will be 1987 thru 1990 Cherokee or Comanche. Chrysler changed to their own injection/ignition system in 1991.

[Pete M]

where is the oil leaking from? rear main seal?

[KMAPRO]

where is the oil leaking from? rear main seal?

 

Pretty much all over....It is really so bad, it is hard to tell where the leak is coming from.

 

I'll post a pic of the front diff and you will see how bad it is.

 

Wouldn't let me post the pic, but you can follow this link and see the pic:

 

http://www.comancheclub.com/forums/viewtopic.php?f=7&t=19145

[Pete M]

if it's "all over" it very well could simply be a valve cover leak. those have been known to get bad and will deposit oil all over the engine.

[KMAPRO]

Unfortunately, the oil leak is only one of the problems.

 

I have a bad ring on the number 2 piston. It keeps fouling out spark plugs. I finally just bought one of those No-Foul adapters and it has worked fine for a month or two now.

 

It also has a hole in the manifold as well.

 

I would like to just yank this engine out and rebuild it, but I can't be without it that long. I am just hoping that I can find a good running engine that I can replace it with. That way I can pull the original engine out, have it machined and get a little more grunt out of it.

 

Thanks for the tip on the valve cover gasket. I will get up under it again tonight and take a good look at it. I will already be good and oily as I have to drop the oil pan on my Dodge to see how much damage I did to it...I am assuming that the whole bottom end is gone on it.

[Wildman]

If you do go with an 4.0 engine swap, in the Renix era, you should have no problems getting it done in one weekend.

 

Just start on in Friday night, and by Saturday night, you should be in real good shape, leaving Sunday for odds and ends, and watching a game or two.

[Darren]

Just bring it to pingpong's house, then you'll be done in just a few hours.

[JACKED88]

I didnt think tha longblock itself had changed. If thats true, why can't he buy a newer model motor and put his 87 intake and exaust on it. There may be a few other little differences like tha flywheel for his CPO and maybe the harmonic balancer but tha longblock itself aughta be tha same. RIGHT ?????????

If not, whats tha difference in tha newer blocks and heads that would prevent him from installing his 87 accessaries on it???

[Eagle]

I didnt think tha longblock itself had changed. If thats true, why can't he buy a newer model motor and put his 87 intake and exaust on it. There may be a few other little differences like tha flywheel for his CPO and maybe the harmonic balancer but tha longblock itself aughta be tha same. RIGHT ?????????

If not, whats tha difference in tha newer blocks and heads that would prevent him from installing his 87 accessaries on it???

The block is essentially the same but the ports on the HO heads are shaped differently and raised up higher. Some people have managed to modify either the HO head or the Renix manifold to be able to bolt them together, but due to the mismatch of the port shapes it's just not a good idea unless you have no choice.

 

Also, the Renix has a temperature sensor down low on the left (driver's) side of the block for providing temp data to the ECU. The HO engines use a sensor in the thermostat housing to send data to the ECU.

[JACKED88]

I didnt think tha longblock itself had changed. If thats true, why can't he buy a newer model motor and put his 87 intake and exaust on it. There may be a few other little differences like tha flywheel for his CPO and maybe the harmonic balancer but tha longblock itself aughta be tha same. RIGHT ?????????

If not, whats tha difference in tha newer blocks and heads that would prevent him from installing his 87 accessaries on it???

The block is essentially the same but the ports on the HO heads are shaped differently and raised up higher. Some people have managed to modify either the HO head or the Renix manifold to be able to bolt them together, but due to the mismatch of the port shapes it's just not a good idea unless you have no choice.

 

Also, the Renix has a temperature sensor down low on the left (driver's) side of the block for providing temp data to the ECU. The HO engines use a sensor in the thermostat housing to send data to the ECU.

OK, so what about a pre HO motor? (01 and earlier)

[Geonovast]

Pre- HO is Renix. Any 4.0 from 87-90 will be a direct replacement. 91+ you start running into problems.

[Eagle]

OK, so what about a pre HO motor? (01 and earlier)

We obviously have a failure to communicate.

 

Chrysler introduced the HO (High Output) version of the 4.0L engine in the 1991 model year. That's the year the heads, manifolds, and ports all changed. Considering that 2001 was the LAST year of the XJ, I'm not sure what you had in mind by calling an 01 or older "pre HO."

 

Your engine is a Renix 4.0L. It was used from 1987 through 1990 in the Cherokee and Comanche only. That's ideally what you should be looking for. You could get an HO engine and put your head on it ... but that presupposes that your valves, guides and seals are all in good shape.

[CWLONGSHOT]

Sounds like your best option is a pre '90 long block. Swap over your tin and acessories to the new motor, drop it in and call it good.

 

OR pick up a good running junker XJ and with them setting side by side, swap the parts!! Maybe there is come CC brothers local that like the beer and pizza you provide in exchange for help!! Call it a lil meet and greet!!! Where are you anyhow?

 

If it where mine, I would be upgrading to a 4.7 /4.6 stroker. :yes:

 

CW