Rebuilding 231oddfire, How To Id Year Of Block

Have a '68 Commando Convertible, have purchased a '69 commando rolling chassis for spare parts, it had a running engine. Starting to rebuild engine from rolling chassis, found it to have a 231 in it. Stamped in block 3.8. Still in oddfire configuration. Keeping as oddfire! Boring .30 over. A few questions, (1) How to determine year of block and heads, appears both have been reworked. (2) Where to get new crank or rebuild current one. (3) 231 manifold appears different than 225, continue to use current Rochester Carb? (4) Will electronic ignition/distributor I up graded 225 to tranfer to 231, any year? Any other info will be greatfully appreciated as usual.

 

Thanks for the info.

 

OF 231 was made "I think" for about 1 1/2 years. They are a good motor. Better oiling system. TA Performance should help you out in ID'ing and parts. Raise the compression and install a better cam and all should be good.

 

We have a document with block and head numbers in the Technical Section, IIRC.

 

231 OF should be HEI from the factory AFAIK.

231 intake has a wider bolt pattern for the carb than does the 225 though they both used a Rochester 2G carb. Just went through this myself.

The 231 intake will have an EGR port at the back left.

As mentioned, 231 compression ratio is lower than the 225 so, the factory dished pistons leave it rather anemic, IMO. Mine seems to be compared to the 225 it had in it. Bump up the compression with maybe a flat top piston and you'll be better maybe. I think the Buick 350 pistons are the same as the 231 OF pistons and could possibly be purchased cheaper.

Check with your machinist about the overbore. Or the folks at T/A. The 231 is, in many respects, just a 225 block punched out to 231 from the factory. I'm not sure how much room is left for further over boring. I had mine bored (I forget how far.....long time ago) and it has always run sort of hot and comes to operating temperature pretty quickly. I am not sure that this is a result of the machining I had done or if it is some other issue by, I am suspicious. Do a little more research than I did before having it done. Maybe just a clean up of the cylinder bores will be all you need, along with flatter pistons.

There's a really good book by Pat Ganahl on the V6 engine. It covers several varieties, including the Buick engines, in detail. Worth the inv

 

Thanks for the info, since my last post I have got new info. The teck #s show my block turns out to be a "turbo block" early 80s, to get compression up, using flat top pistons I can only find .60 over. My very able mechanic was questioning boring more than .30 over until we discovered the turbo aspect. My question's are; anyone know where i can get .30 over flat tops, or what's the feeling about boring the block to .60 over? Whats the difference in the turbo block than the standard 231 block? Should I stick with my 225 fly wheel? The jeepster is mostly used for running around the island I live on, not over 55' or creeping around the Glades at slower speeds.