Jump to content

Recommended Posts

Earlier models (all MJ's) were aluminum.  Later model XJ's (96+) are stamped steel.  The steel ones are preferable if your tired old 4.0 has a lot of blowby....the CCV baffle is at the top of the cover inside and oil is less apt to get sucked out and into your airbox.  The aluminum ones have baffle towers that sit much closer to the valve train and pick up oil/vapors much more readily.

 

Its an easy swap, but you will need a new gasket and have to change up the CCV hoses and fittings.

Link to post
Share on other sites
Earlier models (all MJ's) were aluminum.  Later model XJ's (96+) are stamped steel.  The steel ones are preferable if your tired old 4.0 has a lot of blowby....the CCV baffle is at the top of the cover inside and oil is less apt to get sucked out and into your airbox.  The aluminum ones have baffle towers that sit much closer to the valve train and pick up oil/vapors much more readily.

 

Its an easy swap, but you will need a new gasket and have to change up the CCV hoses and fittings.

 

So if there’s a, for example, 1993 Jeep Cherokee, I’d be able to use it with no issues?

 

Or what about a grand Cherokee?

 

Sent from my iPhone using Tapatalk

Link to post
Share on other sites

4.0 VCs through the end of the 1995 model year were cast a-loo-minum. 87-90, 91-95, and 96-06 are the year splits. 96-2006 are stamped steel with a full length internal baffle to reduce oil pickup in the CCV system. Good luck cleaning inside of it if the engine is sludged. The Renix and HO valve cover baffle tubes can be trimmed down to help reduce air filter lubrication.

 

From what I can tell, Renix era valve covers were not painted so have taken on a dull chalky look, 91-95 VCs were painted with a terrible matte black paint that doesn't stick worth a damn, and 96+ valve covers were painted with a semi-gloss black that holds up pretty well.

 

You can bolt any valve cover onto any year of engine, but the vacuum fittings will be substantially different from a Renix year to an HO year.

 

The 1996 and up gasket does not line up on the bolt holes like the 87-95 Fel-Pro gasket does. It actually lines up on the head bolts with built in pins that older engines will not have. This makes it rather challenging to line up properly. I gave up and swapped my original back on.

 

The 1996+ CCV fittings install differently onto the valve cover, but are more or less compatible with the 91-95 hose assemblies.

 

The oil caps leak on the pre-96 valve covers. They like to break off in the 96 and newer valve covers. Pick your poison.

 

The valve cover bolts are different between 87-95 and 96+ valve covers. Early model bolts are longer. Bolt threads are 1/4-20.

 

My engine does not have severe blowby, so I decided I did not want to deal with the VC gasket leak and possibility of snapping off an oil cap in the later valve cover and swapped my original back on.

dFmElZbl.jpg

Link to post
Share on other sites
4.0 VCs through the end of the 1995 model year were cast a-loo-minum. 87-90, 91-95, and 96-06 are the year splits. 96-2006 are stamped steel with a full length internal baffle to reduce oil pickup in the CCV system. Good luck cleaning inside of it if the engine is sludged. The Renix and HO valve cover baffle tubes can be trimmed down to help reduce air filter lubrication.
 
From what I can tell, Renix era valve covers were not painted so have taken on a dull chalky look, 91-95 VCs were painted with a terrible matte black paint that doesn't stick worth a damn, and 96+ valve covers were painted with a semi-gloss black that holds up pretty well.
 
You can bolt any valve cover onto any year of engine, but the vacuum fittings will be substantially different from a Renix year to an HO year.
 
The 1996 and up gasket does not line up on the bolt holes like the 87-95 Fel-Pro gasket does. It actually lines up on the head bolts with built in pins that older engines will not have. This makes it rather challenging to line up properly. I gave up and swapped my original back on.
 
The 1996+ CCV fittings install differently onto the valve cover, but are more or less compatible with the 91-95 hose assemblies.
 
The oil caps leak on the pre-96 valve covers. They like to break off in the 96 and newer valve covers. Pick your poison.
 
The valve cover bolts are different between 87-95 and 96+ valve covers. Early model bolts are longer. Bolt threads are 1/4-20.
 
My engine does not have severe blowby, so I decided I did not want to deal with the VC gasket leak and possibility of snapping off an oil cap in the later valve cover and swapped my original back on.
dFmElZbl.jpg


Thanks for the info!


Sent from my iPhone using Tapatalk
Link to post
Share on other sites

I would also add to NEVER use a parts store special valve cover (96+cover 'upgrade'). I ordered and installed one on my truck, then battled rough running and rich conditions for a week. Finally realized the valve cover was badly made and was mashing down a few rocker arms all the time. Went to a junkyard and pulled one to use, no problems. OEM FTW.

Link to post
Share on other sites

Also, there is the 93-96 GC valve cover. You might find some on XJs. It is an aluminum VC with the latter 96-up style grommets.  I have one on my 98 XJ. I did use the FelPro rubber gasket for the 91-95. I did adapt a '95 XJ onto my RENIX. I had to cut and splice the CCV tube, as the RENIX is in a different location.

 

Link to post
Share on other sites
On 2/22/2020 at 3:33 PM, mjeff87 said:

Earlier models (all MJ's) were aluminum.  Later model XJ's (96+) are stamped steel.  The steel ones are preferable if your tired old 4.0 has a lot of blowby....the CCV baffle is at the top of the cover inside and oil is less apt to get sucked out and into your airbox.  The aluminum ones have baffle towers that sit much closer to the valve train and pick up oil/vapors much more readily.

 

Its an easy swap, but you will need a new gasket and have to change up the CCV hoses and fittings.

The blowby issue is an easy fix.

 

CRUISER’S VALVE COVER MOD

Most early and even later Renix 4.0s could be bothered by excessive oil in the air cleaner box.

A fix from my old days as Service Manager at a Jeep dealership follows. Information was provided to me from a buddy at JeepTech during those days. I don’t believe it ever came out in a Technical Service Bulletin.

Remove the valve cover and turn it over. Next, remove the fluted tubes that are now facing you by removing three screws on each.

Valve cover flute

Chop 1 inch off each of them. Then, drill a half inch hole as shown in the photo. The flat side of the flute that’s closest to the edge of the valve cover. valve cover flutes (2)

 

Clean and de-burr/sand all rough edges nicely, clean with solvent, and reinstall. Don’t be concerned about the chintzy gaskets that will probably crumble into oblivion when you remove the fluted tubes. They can go back together without gaskets.

Here’s a handy video from my friend Brendan showing more detail.

 

Link to post
Share on other sites

I have three 1991 4.0HO engines (XJ, MJ, and another that was in my CJ at one time, and is now on a stand).  I swapped all three to the later stamped steel valve cover, with threaded type of oil fill cap, Fel-Pro "blue" rubber coated steel core gasket, and slightly rerouted PVC/CCV hoses.

 

They also all have the later rounded style intake manifold (which requires the matching later style power steering pump bracket, which is simpler in design and easier to adjust the belt), replacement aftermarket exhaust manifolds with the "bellows" on the outer tubes (which don't crack like oem), 4 hole fuel injectors, deleted heater core diverter valve, and 1996+ throttle bodies that have the MAP sensor mounted directly on the throttle body which eliminates the one on the firewall and eliminates a vacuum line.  You can extend the wires of the existing connector, or build a short extension harness.  You can also leave the original MAP in place as a back up spare.

 

These were all mods done to the motor that was in the CJ, which became my "template" for the XJ and MJ.

IMG_3864.JPG

IMG_3875.JPG

IMG_4026.jpg

IMG_5188.JPG

Link to post
Share on other sites
5 hours ago, 54bobby said:

does the 4.0 specs talked about here carry over to the 2.5 as far as compatibility and changes made between the different years?

 

2 hours ago, mjeff87 said:

All of the 2.5 covers were plastic, except a few later model years on TJ's (IIRC), they were metal.

First pic is an aluminum 2.5 valve cover removed from a 1995 YJ.  Second pic is an aluminum valve cover removed from a TJ. 

 

They are the same except the TJ one has three bosses along the length of the cover on the driver side, that are drilled and tapped.  However, there was nothing in them when I removed it, and I don't know what they are for.  The YJ one doesn't have the bosses.

 

Both were junkyard grabs, so no idea if they were original.

 

The YJ one was filthy.  I spent hours cleaning that darn thing.  3rd pic was after soaking overnight and 30 minutes of scrubbing.  TJ one was basically soak and rinse.  Change your oil!

IMG_6269.jpg

IMG_5842.jpg

IMG_6037.jpg

IMG_6278.jpg

Link to post
Share on other sites
  • 2 months later...

Not sure if there's any difference in the years, I recently replaced all the vent hoses from the VC with Napa parts.
PNS:
7151365 air intake vent hose
7151367 & 7151366 vacuum harness (both sides)


Sent from my moto e5 play using Tapatalk

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...