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1969 pontiac 400 into a 78 Grand Prix

Discussion in 'Pontiac Grand Prix / Grand Am / LeMans / Bonnevill' started by buzz77, May 10, 2017.

  1. tdvick

    tdvick Master Mechanic

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    I believe those would bolt to either block, '69 and older or the '70 and up. They appear to have bolt holes for either. If your car had a 301, the frame side should already be correct. I think you could bolt these mounts to your block and be good to go. I'm sure the guy selling them could confirm more than I car. I didn't know that they made these adapter mounts. Well, at least they used to...
     
  2. buzz77

    buzz77 Greasemonkey

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    Thanks tdvick,
    Just my luck registered on the forum yet I was never sent the confirmation email to click on and complete the process. I remember that screen name I believe he has posted on here long time ago not sure if he is still registered.
     
  3. tdvick

    tdvick Master Mechanic

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    I'll try to contact him on that site and get him to look here.
     
  4. 84GP455

    84GP455 G-Body Guru

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  5. Mikes455Wagon

    Mikes455Wagon Not-quite-so-new-guy

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    The adapter plates Butler sells will allow the use of the later motor mount on an early block. However, all other body style block mounts don't work right. Once you set both mounts side by side, the difference is easily visible. I tried and ran the f body mounts for awhile, the motor sat too high and wasn't a "bolt in." By the motor being too high, this created other issues with header fitment and header to firewall clearance.
     
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  6. Bonnewagon

    Bonnewagon Comic Book Super Hero

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    Buzz77- that "mechanic" should be keel hauled. He tossed the single most important part for your swap. Idiot. Anyway the Indian Adventures parts tdvick posted looked like winners to me. I also had no idea they were being sold. Probably worth a serious search. Sometimes Ebay has the stock GM units. Anything for F, B, or older A bodies won't work right. They will bolt up- but the motor will sit high and besides the other issues posted, the fan will hit the shroud. I've tried them all.
     
  7. buzz77

    buzz77 Greasemonkey

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    Thanks guys ! I picked up the part from Mikes455. Lets hope i get this thing on the road this summer to enjoy
     
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  8. Bonnewagon

    Bonnewagon Comic Book Super Hero

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    Buzz77- what heads are on that motor? Most stock '69 heads are high compression and may not like today's cat piss gas.
     
  9. buzz77

    buzz77 Greasemonkey

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    They are the stock heads 48?? They would have been too high compression as the rebuild got .030 bored out and decked the heads by like .10. But the pistons will bring it down to about 9.2:1 perhaps a tad less
     
  10. Bonnewagon

    Bonnewagon Comic Book Super Hero

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    1969 #48's?!? According to the Wallace Racing chart [http://www.wallaceracing.com/head1.htm ] that motor was a high compression big horsepower manual transmission beast. [1969 400: 330,335,350/366HP 62/48(MT) 2.11/1.77 72cc] It may even be an HO/RA motor- does it have 4-bolt mains?-what is the block code #? Did you use dished pistons or custom low-deck ones to get the compression down? Pontiac used the same standard pistons for all the motors and adjusted the compression with large and small chambered heads. Look for the 2 letter block code that is stamped just below the passenger's side head. Check it against this chart- [http://www.wallaceracing.com/engine1.htm] You may have a rare motor there.
     
    #20 Bonnewagon, May 27, 2017 at 9:30 AM
    Last edited: May 27, 2017 at 9:36 AM
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