Shortbusdriver

I have not done this myself but in my searches I found that the crankshaft snout is different, people mentioned needing to add a shim to get the crank pully to align with the rest of the components. Otherwise everything else can just be bolted on from the serpentine motor. IIRC there is a 3/8" difference between the serp and v groove crank pully. hope that helps!

You guys are AWSOME!, it would have taken me weeks to compile this amount of information, I'm not so great with computer use-still hunt and peck with the keyboard. The 80's have always proven to be a challenge with auto manufacturers for me, mixed sae and metric fasteners, random part changes at any point during production, even different part numbers depending on trim color! (A late 80's maxima) I still love to repair, restore and to improve these machines! The Crown automotive #3242886 is a serpentine style crank pulley listed as both 2.5 and 4.2 motors,81 to 93 which led me to think the balancer is interchangeable, but if the factory part numbers are different how can that be? It may just be the diameter is different which could lead to overdrive/underdrive options for the accessories? I just don't know. Thanks for the mention of the water pump, in my studies I did find that the v belt type spins in the opposite direction of the serpentine type. I wonder how many people have had cooling issues because of this. Thanks again to all who have chimed in on this subject! I would still be running in circles if not for you!

Thanks jeep driver, that is the pulley that I found that was listed for chevys, I'm going to order one from the locale parts store and compare it to the one I remove from the mj.if it's not the same it can be sent back at no cost. I called dorman and they claimed it won't fit but I'm sorta skeptical about customer service types and I saw a listing for jcwhitney that listed it as fitting the 2.5 jeep motor- it's worth checking out.

Thanks for the part numbers!, those help to eliminate the 4.0 from the equation although some other parts appear to interchange, Does the manual list the 4.2 balancer as being the same part number as the 2.5? I am curious about that since I've found at least two retail sources that claim they are. What I'm having a hard time with is finding a double v belt style, the serpentine style is all that I have been seeing in my search. It may take some time to get all of the info sorted out but in the end may prove valuable to others that are trying to preserve an older jeep, and maybe save a little frustration for them as well! At this point I am going to get the one from saveevryjp1998 and keep looking for a new replacement part, worst case is that I can have the bad one rebuilt and not have to have the mj out of service for a week or more. I will update as I find things out.

That looks right, I'll take it! I will revisit my searches again for more info on your serpentine set up but qtek said 4.0 and 2.5 are the same balancer. I did find crown # 3242886 is listed for both 2.5 and 4.2 motors 1981 to 1993, it has the shoulder on the back like yours appears to in the photos. I did run across mention that the alignment is off by 3/8 inch when using 4.0 pulleys , it could have to do with the shoulder being on the front or back of the pulley. How confusing it all is! Perhaps this info will be of use to others when all is said and done. I also found a dorman part (double v) that looks correct but it's listed for chevy , guess it will take finding all of the measurements ( id, od, offset, etc) to see if it will work on the 2.5 jeep motor.

Thanks to all who have responded so quickly, I have used jeep drivers recommendation and will see if that pans out. In my search I contacted quadratek and was told that the serpentine belt style are the same part number for the 4 and 6 cylinder motors, but no double v style are listed. I did find a place in California that will rebuild the balancer but can't have the mj out of service more than a day, it's his only transportation .

Thanks pete! According to my research so far AMC did use the GM (PONTIAC) 2.5 motor for a few years (early 80's)before creating there own 2.5 motor for the 1984/85 models. The amc motor is an I 6 minus 2 cylinders so the 4.2 balancer may fit the 2.5 , but I don't know for certain, and don't want to get any parts without knowing for sure!

Hi folks! New to the forum and hope to find answers to an issue I can't seem to figure out myself. My friend of 25 years has an 86 comanche that he loves and intends to keep for the rest of his life ( which may not be to long due to cancer returning). The issue is finding a new double v belt harmonic balancer for his 86 2.5 mj. All I can locate are the serpentine style that obviously won't work. I am hoping that someone here has the answer to this problem, I've seen reference to the 4.2 crank pully being the same as the 2.5 with the serpentine belt but have only seen the single v belt type online for the 4.2. I also ran across a dorman part that says it will fit the 2.5 (according to seller) but it is listed for chevy motors only elsewhere! ANY HELP would be appreciated!