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The 4.0L came on the scene in 1987 and is still being used, however 2005 may be the end of the journey in domestic production. It’ll be a bittersweet farewell: most who have it love it. This is an old school inline six with lots of torque and there are still many of them out on the road. Plenty of opportunity for you to see them.

This issue we are going to take a look at the cylinder heads for the 4.0L Jeep. There are four of them and you really cannot swap them around, so you had better know what you have and what fits where.


All years of 4.0L production used cast iron cylinder heads. In 1987-1990 the cylinder head casting number is 2686. The fastest VIP (Visual Identification Point) on this head is the mostly rectangular shaped intake ports (see Photo 1) that have an abnormal looking relief at the top for injector clearance. Note also that the intake ports are facing each other on the front two and rear two cylinders but the exhaust do it on the center two. The exhaust ports are a rounded “D” shape.


The 1991-1995 head castings (c/n 7120 and 33007119) appear identical to the 2686 until you get to the port side of the cylinder head. There, you’ll discover the VIP to be the intake port which now has much smaller relief for the fuel injector and the exhaust ports now look like a squared off circle or a rounded off square depending on your perception (see Photo 2).

From 1996-1999, the Jeep 4.0L used head casting 0630. This cylinder head has two receiver holes for two dowel pins that were added to the block for cylinder head alignment (see Photo 3). The intake ports were changed once again, and there was a newly
designed rocker cover and gasket on the scene, that will not retro back. Also, the move was made to lighter pressure beehive-shaped valve springs and a different profile cam.


Note in Photo 4: the center exhaust ports on this head run off a common port without a divider at the gasket surface. This is the quickest VIP of this head.

The 1999-2005 cylinder head has casting number 0331, and includes the same two head dowel receiver holes. Surprise, surprise: the intake ports have changed once again. As seen in Photo 5 (above) they have gone back to that small relief at the top type port

again, and the exhaust ports are the smallest that they have ever been. The interior of these ports are very rough “as cast” and are very easy to recognize. However the VIP on this head is the spark plug side of the cylinder head where there are four new bosses to mount the coil packs (Photo 6).


That should get you through the 4.0L Jeep heads and keep you out of the “do-over” column. Don’t forget this is the kind of information that you can find when you utilize I encourage you to visit the site and take a tour.

I also need to apologize for failing to list two important contributors in the credits for last month’s “Great Ford Cover Up” article. David Struck and David James of Baseline Automotive, Farmington Hills, MI, provided invaluable assistance in developing the article. Thanks for your help!

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Roy Berndt
Roy Berndt has decades of machine shop experience. He is the Program Manager for PROFormance Powertrain Products, a PER in Springfield, MO. You can reach Roy at [email protected]
  • The Dude

    Hi Roy, have 89 Cherokee which had a 2686 cracked head. Installed a 0331 and used 2686 intake/e gasket to match. Now have a runaway eng. on start up, even with Butterfly Totally Taped Off / TPS and IAC unplugged. Loosing my mind. Is Baby Sis Jeep and charity repair . Please Jelp

  • Matt

    You don’t have your intake manifold fulled seat.

  • Pete Tinga

    The information in the above article is incorrect on a number of points, the most glaring is identifying an old siamesed exhaust port 258 head as being from 96 to 99 4.0 liter.
    The 0630 head wasn’t used in 99. Article needs to be proofed.

  • Maxwelhse

    I can’t comment on your other points, but my ’99 TJ has a 630 head from the factory. I believe it’s a matter of “early” or “late” ’99.

  • Pete Tinga

    I agree, most parts books list parts for the 630 till 98. With 99 being a transition year they don’t list it. I think the 7120 used U-groove keepers were they went back to 3 groove with the 630 so you can’t use 7120 valves in a 630 without swapping retainers and springs.

  • Steven Garcia

    This article is full of errors. What do you mean with “you cant swap them around” and you “better know what you have and what fits where?” Articles like this one really upset me. My inference is that it was written by a person on his/her lunch break. Doing so required about 20 minutes of online research from non-credible sources and was compiled without further consideration.

  • Robert

    So, I have a 95 xj country & love it. I would like to make it a stroker and put the banks turbo on it. The side winder is only for the 99-06 wrangler. Could I use the head & turbo kit on my block?

  • Tree Top flyer

    I am glad you mentioned this, because I was just planning on changing my 4.2L head to a 4.0L

  • Pete Tinga

    Your 95 will have a different exhaust manifold. the 99-06 head has high velocity exhaust ports and a dual split cast exhaust manifold.