1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Rebuilding 231oddfire, How To Id Year Of Block

Discussion in 'Jeepster Commando and Commando Tech' started by Henry Nachtsheim, Oct 12, 2019 at 3:40 PM.

  1. Oct 12, 2019 at 3:40 PM
    Henry Nachtsheim

    Henry Nachtsheim New Member

    Sanibel
    Joined:
    Mar 1, 2019
    Messages:
    10
    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.
     
  2. Oct 12, 2019 at 6:00 PM
    Warloch

    Warloch Did you say Flattie??? Staff Member Sponsor

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    4,467
    (1) Post up the block number from the back side of the block. You can use those to narrow the year down, but don't remember the 231 having the same stamp on the exhaust to fix it.
    (2) TA Performance would be who I would look to if I needed a 'new' crank. Pretty sure the 225 crank would work for the 231 OF as well and might be an option for used as the bore was the change for 231 if memory serves.
    (3) Yes - depending on year it will be. Not sure if the 231 will take the same carb as it depends on what it was in.
    (4) The 231OF and 225OF use the same ignition - I use 231 OF parts in my 225s with HEI
     
  3. Oct 12, 2019 at 8:13 PM
    Henry Nachtsheim

    Henry Nachtsheim New Member

    Sanibel
    Joined:
    Mar 1, 2019
    Messages:
    10
    Thanks for the info.
     
  4. Oct 12, 2019 at 10:57 PM
    Jeepsterjim

    Jeepsterjim New Member

    Lincoln, CA
    Joined:
    Apr 25, 2019
    Messages:
    12
    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.
     
  5. Oct 13, 2019 at 2:43 PM
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    20,102
    We have a document with block and head numbers in the Technical Section, IIRC.
     
  6. Oct 13, 2019 at 5:12 PM
    wheelie

    wheelie beeg dummy Sponsor 2019 Sponsor

    York, PA
    Joined:
    Mar 6, 2004
    Messages:
    3,535
    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
     

Share This Page

New Posts