Posted by Brian in Oregon on Friday, December 07, 2001 at 1:31PM :
In Reply to: Re: WDX---M37 Trucks posted by Tom J. on Thursday, December 06, 2001 at 11:35PM :
The 251 however won't allow the 100 amp charging system to be installed, since it uses multiple pulleys. That's why Canuck trucks needing the extra amperage had a seperate gas fired generator.
The 251 is a good swap from the standpoint of looking original. Very few people know the physical difference between a 230 and 251 and probably fewer could visually spot the difference.
There are certain items that won't cross-swap between a military 230 and a civvie 251. You may have to drill and tap fittings for fording plumbing. Also, there's the question of the distributer. I've read the 230 and 251 distributer won't interchange. I don't know if that's true or not. I do know that the tang in the distributer that mates to the oil pump is offset in the military 230 distributer. The civvie is centered. I don't know if the shafts can be swapped, nor do I know if the military 230 distributer can even be made to fit the civvie 251 block. Obviously a Canuck military 251 engine would be ideal, but how rare are those? This all is a moot point if you don't care to go to the extra lengths to disguise the 251 and make it look like an original 230.
As for the basic install, pretty much the biggest jobs are moving the front motor mount holes forward on the crossmember, and altering where the exhaust pipe meets the exhaust manifold. Probably the easiest engine swap out there.
I've read comments by two folks who have done the 251 swap. They like it and say there is a noticable increase in power. Plus the 251 is not an offset rod engine. Meaning it can take a bit higher revs than the 230. It might do an honest 55 mph if balanced with the stock tires and gears (3200 rpm) whereas the 230 revs out around 28 rpm (45 mph).
I thought long and hard on a 251 or better yet a 265 swap instead of a V-8. I finally came down on the side of reliability, getting away from the older charging system, older carbs, governors, etc.
I wish our military had gone to the 251 engine. (They did in the three prototype XM-195 Field Utility Trucks, which were a shortened M37 that kinda looked like a Land Rover - ie one piece body and cab).