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One thing that’s bothered me ever since I first built the stroker 4.6L engine for Project HMX was the serpentine belt routing. Recall that I got the engine out of a 1993 Jeep Cherokee and that I’ve decided to forgo air conditioning, along with any sort of mechanical fan. I’ve also installed a 1999-up Grand Cherokee power steering pump and idler pulley and I’ve had to reroute the belt slightly to accommodate the Advance Adapters relocated crank position sensor. At the time, the best solution I could come up with used a grand total of four idler pulleys (two traditional idler pulleys and two pulleys reduced to serving as locators for belt routing) and a belt about as long as a Burmese python. Still, it worked.
Not until I bought my 1994 Grand Cherokee, however, did I realize I could have severely simplified the serpentine belt setup. You see, XJs and ZJs might use the same 4.0L engine, but the brackets on the passenger side differ between the two. I believe this was a packaging decision on the Jeep engine designers’ part: The XJ has a lower hood and grille, and uses a smaller offset mechanical fan (augmented with an auxiliary electric fan) versus the ZJ’s larger, traditionally mounted mechanical fan, so the XJ had to reposition the alternator way down low to make room. Thus I found a guy parting out a ZJ’s 4.0L and bought the alternator and air conditioning brackets off him.
With a little sandblasting by Litwin and some aluminum paint, they looked about as good as new. Interestingly, the two brackets weighed almost nothing, and I see an “Mg” cast into one of them. Magnesium?
Swapping the two took a couple hours, and the difference became immediately obvious. With the alternator repositioned higher in the engine bay, I could eliminate two pulleys (the one formerly used to spin the XJ mechanical fan and the dummy taking the place of the air-conditioner pulley) and run a much shorter belt. Here’s a couple before-and-afters showing the new alternator location from above and below:
While disassembling the XJ brackets, I found a film of rubber dust in one area where the belt came too close to a bolt on the timing cover. I believe that’s what was causing a minor, but irritating and persistent, squeal from the front of the engine, so chalk up another good reason to swap the brackets. With it all bolted back together and the right belt in place (using the string method shown in the lead photo), the squeal went away. It’s possible I freed up a little more power with the swap – and it certainly can’t hurt to get the alternator away from water spray and road debris – but I think the real benefit here comes from simplifying the accessory system, making belt changes easier and reducing the number of failure points by two.
Finally, as it looks now. I may have to relocate some things now to take advantage of that unoccupied flat spot. Suggestions?
Posted in Blog
Tagged AMC Spirit AMX, brackets, Hemmings Muscle Machines, Jeep Cherokee, Jeep Grand Cherokee, Project HMX, pulleys, serpentine belt, tech and tools