Juan Grande

Moses, OK, I've decided to just do a 4.0L swap into my 4.2L YJ. Since the YJ will essentially be a Daily Driver, I'm not going the 4.6L stroker option. After analysis, it is more economical to simply source a used 4.0L engine with EFI than it is to retrofit MPI onto the 4.2L engine. As you might have guessed, my research shows that XJ 4.0L engines are more plentiful and cheaper than trying to find a 91-95 YJ 4.0L. My question: Can you point me towards any resources that show how to do an XJ 4.0L swap into a 4.2L YJ? I'm thinking a 92-95 XL engine (I have already found a 95 XL engine with harness, sensors, and computer for $450). I'll be doing a full rebuild on the 4.0L engine. I will also be swapping in AX15/NP231 gearing. I'm fairly comfortable on tackling the harness issue by using schematics. I will most likely change out my YJ fuel tank/sender with a tank that takes the appropriate in-tank pump/sender. I want to be sure I understand the issues with 1) engine mounts, 2) XJ 4.0L serpentine belt reconfiguration for mechanical fan, and 3) what else to be sure to grab when sourcing the engine beyond harness, sensors, computer, and 4) anything else. Many thanks. Juan Grande

OK, I'm getting smarter by the day on this topic. Here is what I learned since Moses' response above. A good deal of my education came from a call to HESCO and some browsing on their forum site. The PCMs are no longer being manufactured. This is why HESCO no longer has the MPI Kit for Manual Transmission; they ran out of supply of the MTX PCM. They still have kits for ATX but they are running out of PCM for this application as well. You can still find MTX kits on the Internet but you can tell supplies are low. I would think this also explains why the price has gone up. I have attached the parts list for a MPI Kit. This shows all of the parts needed if one tried to scrape together the parts from donor vehicles. It has the MOPAR parts numbers and many of these items you can still be found new, including from HESCO. Note that this list is for an MTX MPI kit. I'm making the decision to go MPI for my rebuild. From many sources that I have consulted (including Moses above) it is the consensus best fuel system option withstanding cost. Fortunately, budget is not that tight and the approximately $1K premium for MPI over TBI is worth it to me. I'm looking to have fun with my YJ for at least another 10 years after the rebuild and the amortization of $1K over that period works. Additionally, I'm going to go the 'new kit' route. The swinger for me is the availability of the PCM; even if I can scrape up everything else, I can't get a new PCM due to lack of availability and I would think there is a comfort in having a new PCM Some of what Moses has been talking about above related to headers wasn't jibbing with me. I wasn't seeing the availability of stock header products for the 4.2L engine, in particular I wasn't seeing any 'factory' options. And then it dawned on me that perhaps his experience was with a 4.0L head on a 4.2L engine. (Moses, might this be true?) HESCO confirmed with me that there are plenty more options, including a 'factory' option, for headers on the 4.0L head. I'm now strongly leaning towards a 4.0L cylinder head swap with my MPI upgrade. So that leads me to this: what are the strong, do-it-yourself sources on doing a 4.0L swap? I know about the water jacket issue. What are the most proven techniques to closing these by a weekend warrior like me? Is this something that should be best left to a shop? I know HESCO has cylinder heads that are for sale that take care of this (including an aluminum option) but that may be something that breaks the budget. Anyone have experience on this that they would like to pass on? MOPAR MPI Kit Parts List.pdf

Moses, many thanks for the quick reply. You mention above that the "Mopar EFI kit incudes a factory exhaust manifold (tubular) and EFI port injection intake assembly." My research on the Mopar kit doesn't show any exhaust/header components. How am I mis-interpreting you? My interest remains with the Mopar MPI. Yes, the cost has crept up. Also, it appears that suppliers are becoming sparse, especially for a manual transmission application. I'm curious if anyone has any experience of getting some/most of the components from the junk yard and completing this kit through Mopar, HESCO, or other? Can the be a more cost effective route without adding undue risk?

Moses, I have an '87 Wrangler YJ that I'm looking to refurbish. I would like to replace the Carter BBD carbureted system. I have two questions: I have seen your articles on the Mopar MPI Conversion Kit and the MSD Atomic EFI kit. I'm leaning towards the Mopar kit but would like to see if you can provide a compare/contrast. My YJ will be much more of a Daily Driver with modest off road use. I would like to do a Cat Forward replacement at the same time that I upgrade to a new fuel system (I recently did a Muffler Back replacement). Do you suggest upgrading to a header application for performance improvement? If so, is there a header that requires no/minimum customization (i.e. can share bolt pattern with intake manifold and will follow the factory exhaust path configuration)? If you are suggesting a header upgrade, how choosy should I be with the cat selection? Many thanks.