67 Skylark 340 - 350 Swap?

Discussion in 'Wet behind the ears??' started by Grim Jeeper, Apr 4, 2019.

  1. Grim Jeeper

    Grim Jeeper Member

    Hey guys, I picked up an all original 67 skylark a few weeks ago, 89k factory miles on a 340-2. I bought it with a blown engine with a hole in the block and I'm itching to get it running again. I'm searching for a complete 340 engine to drop in, but haven't been successful. I read online somewhere that a buick 350 with a th350 transmission would drop right in... can anyone confirm or have a 340 for sale in florida?
     
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  2. Grim Jeeper

    Grim Jeeper Member

    I also found a GS 350 engine on craigslist locally, would that bolt up to the existing tranny?
     
  3. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Welcome to v8buick!

    The 350 will bolt right in with the '67 mounts and bolt to the trans as well as the wiring should connect the same as the 340.

    The sbb 340 and 350 are close to the same engine with the difference being the 350 has a .050" larger bore size(3.75" to 3.80") and the heads and intake were changed to flow more air. The crank and rods are the same as the earlier sbb 350 engines with the 340 pistons .050" smaller in diameter as the 350. The block is almost the same except for the cam tunnel and lifter locations.

    If you can though try to swap in a 200R4/700R4 or at least a TH350 trans while you're in there so you have a good 1st gear. The st300 in the car will make the engine seem weaker than it is. A simple trans swap while changing the engine anyway will be a great seat of the pants upgrade. You can always do the trans upgrade later as well so you can feel how sluggish the st300 feels off the line, just realize its the trans not the engine that is if the engine runs good.

    If you can't hear the engine run, then it should be priced as a core, no more than $500. Or should at least be able to do a compression test there to make sure it has good compression within 10% of each other cylinder with around 150 PSI or higher.
     
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  4. Grandpas67

    Grandpas67 Well-Known Member

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  5. Gulfgears

    Gulfgears Gulfgears

    Look at your driveshaft. If it has the rubber inner liner, you may want to replace the shaft with a one piece. Bigger engine might eat it up.
     
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  6. Grim Jeeper

    Grim Jeeper Member

    Awesome, thank you!! I'm going to contact the guy with the 350 GS engine and see if I can pick that up. The th350 trans will bolt right up to the GS 350?
     
  7. Grim Jeeper

    Grim Jeeper Member

    Great thanks!! Ill check that out!
     
  8. 12lives

    12lives Engage! - Jean-Luc Picard

    Where are you? I have a nice running 340 you might want.
     
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  9. Grim Jeeper

    Grim Jeeper Member

    I’m in west palm beach, FL
     
  10. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    That depends because there are 2 different bolt patterns on TH350 transmissions, one that will bolt to the Chevy engines and the other bolt pattern that will bolt to Buick, Olds, Pontiac and Cadillac engines.

    Also you can reuse your cross member and driveshaft. Don't worry about the driveshaft having the rubber insulator, the same design was used all the way to the '71 GS350 Skylark. Not sure if the 455 cars had the same design though but should be just fine for a GS350 engine.

    The 200R4 has a dual pattern that fits both Chevy and BOPC bolt patterns while the 700R4 has the Chevy pattern that will require an adapter plate. And as a side note, the same adapter will work to make a Chevy trans bolt to a BOPC engine that costs around $50.(the 700R4 has the Chevy bolt pattern)
     
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  11. Grim Jeeper

    Grim Jeeper Member

    *UPDATE* 4/13/19
    I was able to pick up a 350/th350 from a '70 skylark. The car was totally restored show car and was receiving a LS swap, and ran and drove into the shop I got the engine from. Seeing the rest of the car, I believe the motor has been gone through before. I just plan to clean it up, replace the valve cover gaskets and oil pan gasket and hopefully she'll be running and driving real soon!
     
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  12. 12lives

    12lives Engage! - Jean-Luc Picard

    Great news - sounds like you got a nice set up!
     

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