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comanche engine swap question


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I have a question about my 89 comanche engine.The engine is about done in it. Its pushing oil into the air box pretty fast and sucking antifreeze into the oil. I was wondering if i pull that motor what would i have to modify to put in a 93 grand cherokee engine. Both are 4.0 strait sixes. Any info would be appreciated. Thanks.

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Ok well i just got done putting a new pcv valve grommet in and am going to clean out the elbow on top. What would i do to stop the oil from going into the airbox. I would definately like to keep the engine thats in it in there. I was just told it had bad rings because of the oil going into the airbox. I know the head gasket is bad and have to keep driving it with work and school. All the exhaust fell off recently too so its obnoxiously loud and i hear thats bad for the valves. I just hope my motors not to far gone.

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I put a YJ 4.0L into an MJ,

and the motor mount brackets were different (brackets between the engine, and the mount).

 

The YJ's offset the engine to one side (drivers/passengers, I forget now), and the MJ mounts offset the engine to the opposite side.

 

I don't know about ZJ 4.0L's, but def check first.

 

I guess you already know the electronics/head & manifolds are different from a Renix to a HO engine.

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Most people who have problems with ther CCV system either replace the whole system lines and all, or get a late model valve cover and its CCV system and that usually takes care of it. It doesnt necessarilly mean you have bad rings.

 

And I think you would only have a valve issue with no exhaust if you were running it with no exhaust manifold, and I'm sure youre not doing that.... most likely fell off after the converter.... right? That will not be an issue for you.

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Ive heard about the other differences but my main concern was mounting it in the same place. I'm just guna hope she doesnt blow and hope the rings really are good in it. It only has 119000 on it so i don't see how it could be that bad.

 

 

Don't forget the accessory drive assemblies on the front will also be different, since XJ/MJ's use an offset, small, engine fan.

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bad rings can cause the oil blowby, but it is FAR more common for a struggling CCV system to cause it. :thumbsup:

 

also, you could just put a catch bottle inline before the filter to keep the oil from getting to it.

 

Have you done a compression test yet? that would tell you if your rings are bad. I'd hate to see you do a whole engine swap for nothing.

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I put a YJ 4.0L into an MJ,

and the motor mount brackets were different (brackets between the engine, and the mount).

 

The YJ's offset the engine to one side (drivers/passengers, I forget now), and the MJ mounts offset the engine to the opposite side.

 

I don't know about ZJ 4.0L's, but def check first.

 

I guess you already know the electronics/head & manifolds are different from a Renix to a HO engine.

 

Wait, lets clarify...the bolt on mounts are different but you will just bolt your stock ones on. I put a 1998 Grand Cherokee 4.0 in my 1991 and everything from the 91 engine just bolted onto the 98. Just get a 96-99 engine (best block, rings, and pistons) and then swap all your Renix equipment and mounts to the newer 4.0. You'll love the PAWR!

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I put a 92 wrangler valve cover on my 2.5L engine and it stopped the oil in the airbox.. I got the fittings from a Jeep dealership, got the valve cover for $25 on ebay and the fittings for about $15 and then new heater hose for the back of the airbox and vacuum hose from autozone for $2.. Fairly simple.

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I put a YJ 4.0L into an MJ,

and the motor mount brackets were different (brackets between the engine, and the mount).

 

The YJ's offset the engine to one side (drivers/passengers, I forget now), and the MJ mounts offset the engine to the opposite side.

 

I don't know about ZJ 4.0L's, but def check first.

 

I guess you already know the electronics/head & manifolds are different from a Renix to a HO engine.

 

Wait, lets clarify...the bolt on mounts are different but you will just bolt your stock ones on.

Yes

I put a 1998 Grand Cherokee 4.0 in my 1991 and everything from the 91 engine just bolted onto the 98. Just get a 96-99 engine (best block, rings, and pistons) and then swap all your Renix equipment and mounts to the newer 4.0. You'll love the PAWR!

 

Splitting hairs,

but I disagree that the 96-99 block is best.

 

In terms of mileage & wear (with decent 91-95's all but gone from junkyards), you're probably right.

And the 96+ block does have harshness/noise/vibration refinements, like the main bearing girdle,

 

but the killer for me is the 96+ pistons.

They got shorter shirts, and the dreaded diesel noise got so much worse with these short pistons rocking in the block.

I've even heard of the rocking, and wear leading to broken skirts.

 

Our 96' has sounded like a diesel since the 40-50k mile mark.

My 98' with 77k miles isn't horrible yet, but the noise is there.

 

Also the 96+'s got a smaller cam vs the 87-95's (for good, or bad depending on your perspective)

 

Again, splitting hairs, but I'll take a 91-95 over the rest. :thumbsup:

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Wait, lets clarify...the bolt on mounts are different but you will just bolt your stock ones on. I put a 1998 Grand Cherokee 4.0 in my 1991 and everything from the 91 engine just bolted onto the 98. Just get a 96-99 engine (best block, rings, and pistons) and then swap all your Renix equipment and mounts to the newer 4.0. You'll love the PAWR!

 

If he puts his renix stuff on a newer 4.0l I doubt he will gain much power,also his renix stuff won't just bolt on to a HO head so he would have to use his head which probably has a blown head gasket and maybe other issues or convert his truck to HO manifolds

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Wait, lets clarify...the bolt on mounts are different but you will just bolt your stock ones on. I put a 1998 Grand Cherokee 4.0 in my 1991 and everything from the 91 engine just bolted onto the 98. Just get a 96-99 engine (best block, rings, and pistons) and then swap all your Renix equipment and mounts to the newer 4.0. You'll love the PAWR!

 

If he puts his renix stuff on a newer 4.0l I doubt he will gain much power,also his renix stuff won't just bolt on to a HO head so he would have to use his head which probably has a blown head gasket and maybe other issues or convert his truck to HO manifolds

 

As long as the only renix stuff he uses is the sensors and mounts (as in he does do the manifold conversion), there would indeed be a very noticeable difference in power. I've had the oppurtunity to sample numerous variations of the 4.0 over the years (3 stock renix's, 1 lightly modded renix, 2 stock HO's and now the HO/Renix hybrid). I'd gladly challenge anyone to differentiate powerwise between the Hybrid and a full HO. Keep in mind though that the power comes in a completely different RPM range. While I thoroughly enjoy the added top end power I do sometimes find myself missing the low rpm grunt of the renix motor. One hill in particular in my daily commute the renix motor would pull up in OD at 1600-1800rpm, HO motor has to downshift to 3rd to maintain the same speed.

 

Also since we seem to have gotten into a bit of discussion on blocks and such I thought I'd throw in my $0.02 on that topic as well. Only really applicable for someone building up a motor (or considering keeping thier current one I suppose). I had the oppurtunity to tear down a few well abused 4.0's this summer and observed first hand one of the major differences in the various blocks. The High nickel alloy of the renix era block is indeed super hard! The 300k '91 block out of my XJ showed significant cylinder wall wear as I expected. The 500+K renix block out of the MJ still has visible cross-hatching the full length of the cylinder walls, even in the cylinder with 2 broken rings. I had heard that the blocks were harder but I was truly surprised to see the real-world difference.

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