Buick 231 Performance Mods

I have two CJ5s with the Buick Odd fire, original install.
I bought a 1970 CJ5 for parts and discovered it has a viable 231 odd-fire conversion in it.
From what i have read the 231 was de-tuned to address the fuel efficiency situation in the 70's.
I do not know the HP and would appreciate if someone could give me that info.
However, the big question is, how can I improve the performance on this engine.
It has the original GM HEI distributor and an Edelbrock carburetor.
Can anyone assist?

 

I put an odd fire 231 in place of my original 225 long ago before I knew anything. Had I known about the difference in compression ratios between the 2, I would have had other pistons put in the 231 to bump the compression ratio back up to 225 specs. This 231 has alwsys seemed sort of anemic compared to how the 225 ran.

Aside from that I have nothing else to offer. The HEI is a plus.

 

A dismal 110hp. Mostly due to compression. It's a fine engine that wakes up nicely with headers / dual exhaust. There are some off the shelf aftermarket cams. It is generally less supported than the later even fire 231 and the 225 dauntless.
I assure you that an OF 231 with 350 pistons ( late 60's higher compression) Offy intake, Holley carb, headers and moderate Crane cam would scatter just about any drive line part you wanted to.

 

Here is the performance book - https://www.amazon.com/V-6-Performa...+v6+performance&qid=1583446126&s=books&sr=1-1

I am surprised that the 350 pistons work with a 231. There's no reason that the deck height would match.

 

9.560 for the 231, 9.543 for the Buick small blocks. So deck the block and it's down to nuances. There's alot of head gasket fussiness with Buicks too that needs watched.

 

The Buick 350 has a taller deck height than the older 300-340. It's 10.187.

It's really obvious between my two Jeeps, the 231 V6 Jeep has lots of room between the valve cover and the heater housing. The 350 in the other Jeep is almost touching it.

 

110HP gross or net?

 

Post-1970 it should be net. 110 seems on par for the displacement and the era. The '72-78 AMC 232 was rated 100 hp.

 

I agree. That being said, 160HP gross will not be significantly more than 110HP Net, so the likelihood of a significant variance between the 225 and 231 might well not exist.

 

Thanks y'all.
I ordered that book last year but it was never shipped. Ordered again tonight.
The 231 has headers and I will start it in a few weeks to check it out. if I did put in a cam what do you suggest?

 

This is what I put in my latest build
Dual Pattern Supercams™ [117125] - $230.00 : ISKY Racing Cams, Do It Right
These engines are limited by the small valves. In general Buicks don't like to rev much over 5k. More duration will push the power band up in the rpms. Schneider also grinds some 231 odd fire cams.

 

look up T A Performance. They specialize in Buicks.

 

the cheapest mod you can do is gasket match the intake and exhaust ports then do a bit of die grinder work on the ports inside to smooth it out. I think I got the 252h cam too..it was an rv cam. can also put a spacer between the carb and intake to get a bit more fall for the fuel and air and of course headers

 

Allegedly, my 231 OF was built similar to what Rich M. mentioned above. It supposedly makes 180 HP now. It was built for a sandrail, and destroyed the VW rearend on the rail...again, allegedly. It does sound like all those mods were done though, so I 90% believe it.