questions on 4.0 to 4.2 head swap. -
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Unread 09-11-2013, 10:50 AM   #1
Registered User
1990 YJ Wrangler 
Join Date: Nov 2011
Location: atlantic, iowa
Posts: 184
questions on 4.0 to 4.2 head swap.

hello. I have started a build thread but this was a specific question I had and I need some help quickly because I am about to tear into this project.

I had a 4.0 engine out of a 93 cherokee that I rebuilt and planned to put in my 90 wrangler. I had some problems with the cherokee engine so we pulled the head off it when we pulled it out. this engine is freshly rebuilt with very few miles on it, the head was reworked with new valves, valve springs etc. I had a collapsed lifter on the 4.0 so the rest of the engine appears to be in good shape.

however after reading on here and thinking about it a lot, since I already have the head off the 4.0 and the 4.2 has less than 70,000 miles on it, I decided to just swap the head onto the 4.2 this was suggested by someone on my build forum and I have been thinking about and decided to go that way. I have read up on the swap quite a bit but I have some specific questions.

1. I bought a COMP Cams Xtreme Energy 4x4 Cam part number CL68-231-4. when I built the engine. is there any reason I should not use this cam in the 4.2 when I swap the head since I am going to put a new timing set on anyway. also I have a new set of lifters that I was going to put in the 4.0 will they work with the 4.2?

2. I also bought new pushrods for the 4.0 from hesco. will they work in this swap or should I re-use the ones in the 4.2?

I think I have the rest of the swap relatively under control, but finding info on parts compatibility between these two engines is difficult. the application tab on the summit website for the cam says it should work but I want to check with the experts on here before I did it.

I am also going to be doing a fuel injection conversion at the same time. I appreciate any help.

My yj:
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