Originally Posted by bowenboy
You seem like you know what ur talkin about. In your opinion, what would you do? rebuild the 225 or 231. I have both available. I know the 225 runs bc I drove it before i took the jeep apart but I don't know the history of the 231. It came with the jeep when i bought it. which is the better option?
Why do you think the 225 needs to be rebuilt? Just asking. Low compression, knock, etc?
Better option? My personal bias is run the 225. I just like the way it sounds and it's original. Other thing it has going for it is the flywheel.
The flywheel of a Jeep V6 is ~50 lbs. really helps keep it moving at low RPM, very advantagous for a Jeep. The flywheel can be put on a 231, an odd-fire 231 is ballanced externally, but an even-fire 231 is internally balanced so you'd need to have the flywheel balanced to the crankshaft.
A common weak point of the 225 is oiling. If the oil pump is in good working condition I don't think that's probably an issue. Mine runs ~30 at idle and 50PSI when driving with a stock pump and Melling girdle and TA Performance adjustable pressure regulator. I've outlined that in an article here: http://earlycj5.com/tech/engines/225...mp/index.shtml
Since you don't know the history of either it'll be roughly the same to rebuild and run either one. I'd keep the 225 unless the block is just trash. Since it's still running I'd think it's in rebuildable condition if it needs it.
I've got casting numbers on my site in the link I gave you to read that'll tell you what the 231 is.