Written / Photographs by: Tony Carricaburu
Now that the 4.0L head is mounted and ready your going to need a 4.0L header or exhaust manifold. For my application I had a friend that had a spare 4.0L header form an 88' Jeep Cherokee lying around. Since my project is on a budget I went ahead and put this header on for now. I highly recommend using a Borla header. Be aware that the intake manifold and exhaust use a lot of the same mounting bolts. There is no need to customize anything, except you'll need to mount the intake manifold and exhaust at the same time. There is also a specific torque sequence and lb. amount for these bolts as well. I created another chart to specify these torque sequences. Torque the Intake/Exhaust Manifold to 23 ft/lbs. (Click on Diagram 1.2 for printable size)
Diagram 1.2 Torque Sequence
After completing the installation of the new Head its recommended that you use different spark plugs. I read a very informative similar article that Tim Weaver produced and he states that for this conversion you will need to use Part Number: RC-9YC4 spark Plugs. Gap at .035". For my Jeep I bought Bosch Platinum platinum +4 plugs. There a little more expensive and I'm not sure if they will even make a difference but I figured I would go ahead and give them a try. Torque Spark Plugs to 27 ft/lbs.
From here go ahead and put your carburetor back onto the intake manifold including all the vacuum lines, fuel lines, etc. as you took it off. Hopefully you marked all the hoses and lines so that they can easily put back in there proper locations. If not the vacuum diagrams can be obtained in the Chilton or Haynes repair manual. Everything should bolt right back into position except the rear power steering pump-mounting bracket. This needed a little modification, which is pretty self-explanatory upon installation.
ADDITIONAL SUBJECT LINK:
4.0L HEAD CONVERSION FINAL EVALUATION:
The overall conclusion of my 4.0L head conversion was definitely two thumbs up. The cost was fairly inexpensive compared to the amount of power gained. Although I've done minor engine repairs and modifications before, I have never done anything even remotely close to this and to my surprise it was pretty easy. The overall preparation, old head removal, and new head installation took about 5 - 6 hours. This may vary depending on the tools used. If you're using Air-Tools be careful not to strip and bolts. I can't say exactly my overall results of the power since I'm currently adding additional engine modification. (See next months Issue for more details) I can say that from speaking with Hesco and other Fellow Jeepers on the Internet that have performed the same conversion the overall performance increase is substantial and well worth the time.
TO GET STARTED ON YOUR 4.0L HEAD CONVERSION, CONTACT KOLLER DODGE AND THEY CAN HOOK YOU UP WITH A REMANUFACTURED HEAD AND NECESSARY PARTS TO CONVERT YOUR JEEP. SEE INFORMATION BELOW FOR DETAILS.