225 rebuild with a 231 block?

The Buick V6 in my 64 CJ6, obviously not the original motor, has odd fire valve covers and distributer and a single barrel intake mani with a single barrel Rochester, but the block is a 1981-79 even fire 3.8 casting # 25506397. I haven't had a chance to drop the oil pan to check the crank yet. Im just wondering if this motor is really an even fire with odd fire parts or if someone rebuilt the odd fire with the 3.8 block.

 

Thanks Warloch. I guess thats what they did. I dropped the oil pan and it has an odd fire crank. I wonder if the heads would be odd fire or even fire or how to tell them apart.

 

The heads don't have freeze plugs and I heard the 231's do. I weighed the fly wheel and it came in at 45lbs. Here are some pics.

 

Thanks again Warloch, but I may look into getting that book myself. I thought I read somewhere that 231s had plugs in the heads but who knows. This motor ran good when I pulled it so now that I know exactly what I have I'll start scrounging the junkyards for upgrades, that is if compression and everything else tests good. I don't understand why they didn't use the intake, carb and distributer from the 231. So i guess thats what I'll be looking for... 2 or 4 brl intake and carb, HEI, and maybe some late model heads. I wonder if any 225 or 231 intake will work? Also I wonder if there are any pros or cons to an even fire 231 converted to an odd fire? Is it just as good as a 225?

 

Those look to be 231 rods. They don't have nuts on them or balancing tabs on the beams.

225 heads use cast aluminum rocker arms instead of stamped steel ones like the 231's have.

 

But that is an odd fire crank right?

 

Ok I'm confused... doesn't take much to do. I thought that the even fire crank had offset journals. I think I'll remove two of the rod ends and see if the journal is offset. Maybe the only thing on it thats odd fire are the valve covers. Can anyone tell by the distributer cap if its odd or even? Thanks for the help guys.

 

Oddfire cranks share connecting rod journals. Evenfire cranks have separate journals for each con rod.


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x2 oddfire will look like a v8
even looks like someone messed up the mold

here is a link to a comparison, it is about 4.3s but the same concept
http://www.nwstp.com/tech/odd.htm

 

To me the crank looks like an oddfire crank because the rods share the same journal and are not offset from each other. I found the same link that jwjeep60 posted and thats what I based my hypothesis on. Do you guys not agree? Today I started to take two rod ends off that are on the same journal so I could see if the journal was split, but it was obvious upon inspection that the rods that share the same journal are on the same plane. Is there something I'm missing or not grasping? Is there another way to tell if its odd or even?

 

The pics posted show an oddfire crank. The evenfire is obvious as the split journals of the evenfire are pronounced. The valve covers indicate 225 heads also. A pic showing the front of the head where the valve cover and head meet may clear up what heads you have. The outside of the 225 heads extend farther up vertically which makes the valve covers more level like the old nailhead Buick V-8's. 231's have the valve covers more angled. More perpendicular to the 90 degree angle of the cylinder block which puts them at roughly a 45 degree angle from horizontal.


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Thanks Nickmil. I thought everyone was telling me I had an even fire crank and it didn't make sense to me. So I guess I have an oddfire 231 built from an evenfire 231 block & O.F. 225 parts?

 

I saw your edit Warloch... everything makes sense now. Congrats on the grandson, I have a year and a half old daughter and those cute little boogers can be distracting.

I removed one of the valve covers and it has cast aluminum rockers and I think I'll take your, Warloch's, advice and pull a head and check the passages out. I also have Pat's book on the was so that should help clarify things and possibly answer some of my questions. Now that I know what I have I think I'll replace the oil pump, timing chain and gears,and maybe the water pump. Can you guys think of anything else I should replace while the engine is out? Im also going to try to find an HEI distributer for it and I was thinking about replacing the heads with later model 231 heads that flow better along with matching intake and 2G carb. Do you guys see any problems with my plan? Thanks again for all the help and advise.