231 to 350 swap (Help!)

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

  1. noraarm

    noraarm Well-Known Member

    Okay guys, i've been shopping around looking for an engine and i have a few more questions.

    Is some rust okay on the engine block and or intake manifold? as long as it isn't deep? and is that fixable?

    Also, if i find one with a automatic tranny will it fit no matter what or does it matter?

    Oh, and will a 350 with stock headers fit my current stock exhaust?

    and how old of motor should i get? is like a 68' or 69' to old?
    would i be able to use unleaded gas with an engine that old?
  2. V8WagonDreamin

    V8WagonDreamin New Member

    I'm getting ready to do this swap and from what I've read i should save myself a few dollars and just buy the motor. I've got a 78' Skylark with the 231 and found a 71' Skylark with a running 350 at a local salvage yard. If it's not necessary, the money not spent on the transmission would do great things for my suspension. I'm fairly confident my transmission is in good working order.
  3. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    The Buick 350 should swap right in with minimal modifications (like to the fan shroud, fuel line length, etc). If you have the TH200, I would upgrade to a TH350 or TH200-4r. The TH200 is probably okay at stock power levels though. Likewise the rear 7.5" differential.

    For some reason my space bar doesn't do anything in the PM's so I answered here.
  4. partsrparts

    partsrparts Silver Level contributor

    i did this swap last year, 1968 350 into a 76 skylark, like Silver Buick says, it's a pretty easy swap, i went with the th400 with the short tail shaft trans and only had to move the cross member back to the next set of holes. and then had to shorten drive shaft. if your'e going to change trans and rear end do it at the same time because when i went to a 8.5 rear i had to have the drive shaft shortened again. the v6 motor mounts will work on the 350 but the 350 mounts are much beefier. (i broke the new v6 mounts in no time at all then went with the 350 mounts).

  5. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    For clarification, you mean the rubber mounts and not the metal frame mounts right? Even my old 231 used to eat the rubber mounts regularly.
  6. partsrparts

    partsrparts Silver Level contributor

    yes, the rubber mounts, v6 rubber mounts compared to 350 rubber mounts is like apples to oranges
  7. V8WagonDreamin

    V8WagonDreamin New Member

    From the research I've done I'm about 95% certain the car already has a TH350 in it. I'm going to decode the VIN to be certain, but if this is the case it should be a matter of pulling the old motor, moving the cross member and dropping in the Buick 350, right? I just want to be sure because I know how often GM liked to make small changes to their parts.
  8. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    Just take a pic of the pan of the transmission and we can ID it for you.... For a simple swap just leave the trans in place and bolt the Buick 350 in place and no messing with the cross-member or driveshaft.
  9. V8WagonDreamin

    V8WagonDreamin New Member

    I'll get a picture of the pan up in a day or so, I work night shift so it can be difficult to get to the car sometimes but I've got a couple days off. I won't be beating on the car as it'll be a daily driver so there shouldn't be too much stain on the transmission in there
  10. MrSony

    MrSony Well-Known Member

    The TH200 should say METRIC on the pan, for any of those who stumble across this in the future. And the Th250 yes, 250 will have a band adjustment screw above the cooler lines on the transmission. TH350 will not. I know the last reply on this thread is almost a year old, but when you have a 231, if you aren't throwing boost at it or nitrous, there's really no reason to not upgrade to a 350 buick. Everything bolts up, brackets, water pump, timing cover (might have to tap new hole sin the bottom depending on the year), pulleys, wires, starter. My old 231 starter is more than enough to turn over my 9.5:1 350. If you want to use the oil light in the dash (regardless of make/model), grab a brass tee and the oil pressure sender of your choice and install like so.

    Attached Files:

  11. newmexguy

    newmexguy Well-Known Member

    The 200 is also a one piece trans, without a removable tail shaft. Would not put any money into one. A light duty "disposable" trans for the late seventies/early eighties smogged cars.
    MrSony likes this.
  12. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    For now just get it up and running with your existing trans and you can do a trans swap later if you have to. Take a pic of the trans pan??

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