Well I planned on a rebuild...

Well I planned on a rebuild...


San Antonio, TX
1980 CJ5
... but it looks like I'll be doing a swap instead. Whoops!


Just bought the Jeep on Monday with the understanding that the motor needed to be rebuilt or replaced, but had been told it ran. Well, after cranking on it for a little while to try and get more than a sputter, she finally gave in! Found the chunk of iron on the ground in a puddle of coolant. Made my decision to swap for a GM motor a little easier...
That is hardcorp, I hope the powertrain swap goes well. :chug:
Is that a 258? Not sure how you use your Jeep but unless the 258 leaves you short on torque a lot I'd stuff in another 258. They're great engines and can be found very cheap, though my Jeep does have a 304. And if my 304 goes up in smoke I'll drop in a 360 before I do a rebuild or a swap.

Nothing against the SBC, I just don't think it's worth the hassle or expense to do it. Especially if your current tranny isn't up to handling 350 power. That's even more work.

Dad and I did a 350/SM465 swap into his 74 and it was quite a lot of work. The tranny needed to be torn down and reassembled with an adapter shaft to couple into the Dana 20, which wasn't cheap. And that tranny is a big pig that barely fits between the rails. After all that he'd like to tear it all out and get back to a 258 for some reason that I haven't figured out yet.
Hi Chilly - Thanks for the input!

It is the 258 I6, and prior to buying I'd been told it had been rebuilt once in its life. I knew to expect the worst, as the guys told me they intentionally tried to lock it up as they had planned on doing an SBC swap and wanted to have some fun. I wasn't too concerned about that, as my goal was to find a Jeep with the least amount of rust and worry about the powertrain later. This one met that requirement. Seems like every other one I looked at before had rotted tubs, frame mounts, and crazy owners.

Anyway, I'm not opposed to dropping in another I6, especially since that would mean I don't have to source adapters, brackets, etc. However, my experience lies with all things SBC, so that's what I'm comfortable with. I've kept my eye out for used 258's around here (or at least good cores) but haven't had any luck. I've got a line on a fairly low-mile Vortec 350 w/ harness, but not sure I want to go through the hassle of fuel injection and PCM. I could always throw a carb on it though. If I did go that route, I'd keep the D300 and T176 though. Decisions, decisions...
Was it cylinder #6?
I think there is something up with #6, the CJ5 I bought had a rod knock and when I tore it down the #6 had a spun rod bearing. I wonder if they don't get enough oil.
It generally is #6 for several reasons:

  • Farthest rod away from the oil pump
  • As wear occurs the pressure drops and flow increases in the nearer rod bearings - #6 gets starved
  • Generally the hottest running cylinder - airflow
All the AMC 6s and Chrysler slant 6s I've seen in junk yards with a thrown rods have been #6.

Anybody else noticed this phenomenon?

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