231 to 350 swap (Help!)

Discussion in 'The "X" bodies' started by noraarm, Sep 29, 2010.

  1. noraarm

    noraarm Well-Known Member

    im seriously inquiring in swapping my baby 231 for a buick 350 but i have some questions i need help on. my car is a 1978 skylark stock 231 w/ auto trans

    1) does it matter what rear end i have? not 100% what that means exactly

    2) will my transmission need to be changed as well from what it is now? (not 100% about what trans it has)

    3) i remember someone telling me that only a radiator hose needs to be changed from a 231 to 350 but is that correct?

    4) on a difficulty scale from 1-10 how hard would this be? i dont have a time limit and i can follow instructions well.

    Added

    5) if i get a 350 with a 2 barrel intake can i use the carb off my 231 on it?

    thanks in advance guys!
     
    Last edited: Sep 30, 2010
  2. bob k. mando

    bob k. mando Guest

    1) does it matter what rear end i have? not 100% what that means exactly

    in this case, i think you would be referring to the ring/pinion gear set your housing uses, both size and ratio.

    larger ring gear sets are stronger ( 8.5" better than 8.25" ) . higher numerical ( shorter ) ratio gear sets get you off the line faster but will cost fuel mileage for cruising and may make your highway rpm uncomfortably high.

    a 200r4 trans would be a good choice for this car, especially if you want to move to a shorter ( 3.73? ) rear gear.


    2) will my transmission need to be changed as well from what it is now? (not 100% about what trans it has)

    the Buick 350 will bolt up in place of your 231. be sure not to use a Chevy 350, that will have a different bell housing.



    4) on a difficulty scale from 1-10 how hard would this be? i dont have a time limit and i can follow instructions well.

    the 231 is a SBB 300ci v8 with two cylinders knocked off and the 350 bore ( the second variation of the Buick v6 was 225ci or 6/8*300 ). the 350 is also a SBB but it has a taller deck and is also necessarily longer than the v6. so there may be some minor fitment issues around the steering shaft or with headers or the fan shroud but all of the fuel lines/electrical/starter/etc should route to the same places.
     
  3. noraarm

    noraarm Well-Known Member

    will the one i have be strong enough for the power of a 350? not 100% what i have, is there a way i can tell? i have a manual for my car will it tell me in there?
     
  4. David G

    David G de-modded....

    I believe the Buick 350 was an available optional engine for your car, which may simplify the installation.
     
  5. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    I'm the one that likely said you'd only have to change out the radiator hoses, and I stand by that. My 455 was practically a drop in, only I had to change the metal frame pads, which you would not have to for the 350. I had to use longer v-belts and I'm 90% sure you would not have to. The wiring was more than adequately long for the 455, the 350 should fit easily, same plugs, same connections to the HEI and sensors. You'll have to either get a new HEI or change out the reluctor and pickup coil in your 231's (that's what I did for the 455).

    What ever trans you have it will bolt up to the Buick 350 with zero issues. If you have a TH200 (how certain are you that it's a TH350?), a 2004r trans bolts right into place of TH200 (because it should have a long tail shaft). It was the first mod I did to my Skyark, TH200 to 2004r, I didn't even modify the drive shaft.

    The rear axle should be a 7.5". My '77's was with 3.23 gears, but your's could easily be 3.08's. In any case, the 7.5", if currently healthy, should be plenty strong for anything but the most radical 350 build or turbo application. I abused mine for ~10 months with a 455, with no issues, though I was concerned about it. Stepping up to an 8.5" wouldn't hurt.

    As for the 2bbl carb, it will bolt on, but the jetting/etc might not be right. And in my experience a properly tuned Q-jet will do better than those rochester dual jet's. Get a 4bbl intake if you can, you'll be happy with the power and mpg's.

    On a scale of 1 to 10, with ten being the easiest, it's an 11, plug and play.
     
  6. noraarm

    noraarm Well-Known Member

    I have no idea about anything about my transmission..

    also about timing? i have no idea what it is or if i need to do it when i ut a 350 in...
     
  7. speedtigger

    speedtigger 9 Second Club

    I would think that transmission and rear end would be fine for a stock 350. Dont use the carb off of your v-6. Use the correct carb for the 350. I would be very surprised if you do not have to change the fan shroud. I would also make sure the radiator is up to the task. Other than that, I would research the motor mounts.
     
  8. noraarm

    noraarm Well-Known Member

    i know the fan shroud will have to be changed i could probably just hack saw it if i cant find one locally.
     
  9. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Ha! The fan shroud does not in fact need to be changed! There are two staples that hold the extension on the shroud. Remove the staples and the extension comes right off and the 350 will put the fan neatly in the middle of the shroud.

    Buick 350 motor mounts are identical to Buick 231 motor mounts.

    Your picture from your thread.
    [​IMG]
     
  10. speedtigger

    speedtigger 9 Second Club

    Sounds like the 231 is just a temporary place holder until the 350 is installed. :TU:
     
  11. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    This is my car with a completely stock Buick 455 in it. That is the stock 231 fan shroud.

    [​IMG]

    [​IMG]
     
  12. jeff0547

    jeff0547 Beaters are Better

    Maybe this will help. These are pics of the pans of GM automatics (bottom of the transmission).

    (1) Print this page.
    (2) Crawl under your car and locate the transmission.
    (3) Compare these pics to what you see.


    This is what I do to indentify GM auto's.:Do No:



    [​IMG]
     
  13. noraarm

    noraarm Well-Known Member

    thank you very much! i will check as soon as i can!
     
  14. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    I think you've seen this video, but this is me abusing the stock 7.5" diff. The gap in the the rubber is me hitting second gear. If you don't put slicks on the car it'll likely live a long long time.

    http://www.youtube.com/watch?v=R_CCLSwdLhU


    **Oh and that was with the engine in the earlier pictures.
     
  15. noraarm

    noraarm Well-Known Member

    so will everything else under my hood fit without any problem? can you tell from the pic?
     
  16. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Yes. The Buick 350 was an OEM option, so it'll definately fit like OE. Brake Booster, Steering Shaft, Firewall, Control Arms, the Accessories, all easily fit.
     
  17. noraarm

    noraarm Well-Known Member

    awesome! thank you guys so much! now its just the quest to find a (kinda) cheap 350, hopefully will be doing it by December, im moving in the first 2 weeks of October so no real extra cash. but i do get a 2 car garage at our new house :D haha what exhaust are you using with your 455? i really like the sound. Also is adding a tach easy? im looking up how to install them but im not 100% where my coil is?
     
  18. pphil

    pphil Well-Known Member

    you have an HIE dist so you have no coil..........
    the tack works with 3 wires 1 to the light switch 1 to a ground and 1 to your dist thats it its simple

    scott
     
  19. noraarm

    noraarm Well-Known Member

    haha alright thank you very much, like i said i dont really know a lot but im learning. so i should look for a 3 wire tach?
     
  20. noraarm

    noraarm Well-Known Member

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