newbie 331 question

[50ChevyFrank]

Joined this group just today. I have already read several posts about the Reo 331 gas engines; how rugged, durable, strong, etc. they are. And some about swapping them out of a deuce in favor of a diesel, etc. Has anyone swapped one into something else? Like a 50 Chevy pickup? I don't really know anything about them other than seeing some ads for them for sale at some of the surplus houses. Does anyone have HP and torque specs? How about length, height, width? Do they have a standard SAE flywheel housing bolt pattern? What trans will bolt to them? Weight? Are spare parts readily available? My 50 3/4-ton still has the original 216, and besides some blow-by and using too much oil, it runs well and the truck drives good. I have been thinking about a re-power and there are lots of options. I want to do anything but another cookie cutter SBC. A 302 GMC is a common swap for these style of trucks. I even considered different diesels... But if I could put a Reo/ Continental OA-331 from a "army deuce-and-a-half" I could hire out pulling stumps . Wouldn't be another one parked beside me at the Cruise-in.
Really the truck is a driver, not pretty, and I want to be able to haul a load and pull a loaded trailer.
Comments? Thanks.

 

[50ChevyFrank]

wrong forum

is there a better forum for these questions??
Is there a tech section??
I will look around some more.

 

[Chevytruck]

wouldn't the M35a2 power plant would be a little too big for a 50 Chevy?

 

[50ChevyFrank]

dunno

Maybe it will be. Having not seen one I don't know. That's why I want to learn more about them. Get dimensions and specs.
Thanks.

 

[hippiedude]

You should look for a GMC 302 , I think it would bolt rite in ........ Wellcome ........ Tim

 

[54reo]

wouldn't the M35a2 power plant would be a little too big for a 50 Chevy?

A OA331 is not a M35A2 power unit.

 

[jatonka]

The OA-331 makes 146 horse power at 3400 rpm. It weighs 871 pounds without accessories. It is about the same size as a GMC 302. The bell housing is a standard SAE round. It will mount a Spicer 3052 transmission. JT

 

[50ChevyFrank]

302

Having done some research on stovebolt.com and oldgmctrucks.com I agree that the 302 is almost a bolt-in. And a popular swap. The 331 Gold Comet may not be right for my Chevy, but it would be different. And I would think a motor big enough to propel the M-275 should move my little pickup down the road....

 

[JasonS]

I have done the 302 swap on two Chevy pickups. It is fairly easy. The 302 is about 1-7/16" longer than the Chevy engine meaning you have to relocate the radiator and front motor mount. The best thing to do is to get a GMC radiator and radiator cross-member. Use the top half of the GMC cross member and the bottom half of the Chevy. This will retain the structure rigidity of the crossmember. I used a flat plate to bridge the distance between the frame and front motor mount.

The 331 is a fair bit longer than the 302 and lots heavier. You would have to cut into the firewall to make it work and most likely remove and rebuild the rear motor mount cross-member. I am sure that it could be done and have thought about it myself for my 302 powered pickup. The Reo literature of the day advertised replacing the GMC powerplants with Reo engines but light duty pickups were probably not what they had in mind. I drove a 302-powered '50 chevy for 10+ years. While it was fun, the GMC takes significant money to make power and even then you have an antique 4-main engine with siamese intake, requires block machining for full flow oil filter, etc. Contrary to the popular opinons on stovebolt, the 302 is an economy truck engine; not some magical engine heaven. GMC didn't put any real effort or technology into it's sixes until the V-6 came out. Take some time to compare the Reo's and GMC's features and design.

I am in the process of putting a Heidts IFS and SBC into that same '50 Chevy (now my dad's truck). It is not that hard and what I would recommend for anything that you want to drive very often. BTW, the aftermarket sway bar for the straight axle is not very effective.

 

[50ChevyFrank]

Thanks

I appreciate your first-hand experience Jason.
Thanks to everyone esle for your comments. It has given me more to think about.

 

[JasonS]

Some additional information.

 

[Recovry4x4]

OA-331 is a sleeved motor. It can be rebuilt for a lifetime. Pure industrial engine. I think it would be very cool.

 

[50ChevyFrank]

Thanks

Thanks for the pics! I appreciate everyone's comments. I have been studying on this project for a couple of years - so I am not in a hurry. I love inline 6-cylinders so I have been thinking all along about a bigger 6. I don't really have anything against V8's. I had another 50 Chevy that had a 307 in it when I got it. High school Ag shop project I was told. From the back of the bellhousing on back was original. It drove good with lots of umpth. And it wasn't tired out at 60 mph. (That's really the one I should have kept - 90% rust free with a nearly perfect original chrome grille...) The diesel dreaming is probably just that, dreaming.
Thanks!!

 

[50ChevyFrank]

I found a Gold Comet for the right price. Now I need to find the correct bellhousing/ adapter to mount my SM-420 trans. From the scanned pages JasonS posted Reo must have offered the trans adapters for GMC's with the SM-420. I wonder where in the world one of them can be found now?? What standard SAE # ring does the 331 have? Is that stuff "standardized"? I know Detroit built adapters for the standard GM trans. Will that work? Any helpful comments 'preciated! I know lots of other details will have to be worked out.

 

[JasonS]

Both SAE #2 and #3 bellhousings were available. Most likely, if your gold comet is mil surplus, it is a #3. The SM420 adapter need not be specific to Reo; others may have also also offered it. However, you may want to consider using a spicer 5 speed from an early M35. I did a search on google for "SM420 SAE #3" and found the following possible leads:
TLC FAQ - 21.2 Diesel Engine Swaps
Isuzu 4BD-1T / NPR Box Truck Revisited... - Pirate4x4.Com Bulletin Board
http://www.thedieselstop.com/archives/abol/PWRSTRK3/messages/$WEBMSG00000000060C2CD623.htm

Also keep in mind that Reo offered a 400 cubic inch version with 200Hp and 364ftlb torque. Same external size as the 331.

 

[JasonS]

I also suggest converting to full flow oil filter. As easy as bolting an aluminum plate to the block; unlike the 302 which requires block machining.

 

[50ChevyFrank]

Thanks again. The 331 I found is from an M35. That means SAE #3. The owner also has the trans (3052) and some other stuff that he really wants to keep for another project. I did not know about the 400" engine. What was it found in? Thanks for the links. I am a regular visitor on the 4btswaps site and about 6-7 other forums. Somewhere I should be able to find a bellhousing that will fit my trans, or get a different one.

 

[50ChevyFrank]

The more I learn about this motor the more difficult this swap seems to be. The 331 is several inches longer than my 216. I will probably have to cut into my firewall and re-do the rear mount/ crossmember, etc..... I'm a good mechanic but not a welder or bodyman. Better look elsewhere. THANKS everyone.