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Technical Powerglide to 350 swap

Discussion in 'Traditional Hot Rods' started by PeggySue, Nov 4, 2020.

  1. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Getting ready to pull my older cast iron power glide in my 55 to install 350 turbo. Will the powerglide cast iron bell housing with the starter mount come off to, What I'm looking at is about a 3" piece between powerglide and motor where starter also mounts in If it does it will change my drive shaft length, is why I ask.
     
  2. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 34,075

    Jalopy Joker
    Member

    what motor do you have?
     
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  3. Mr48chev
    Joined: Dec 28, 2007
    Posts: 35,977

    Mr48chev
    ALLIANCE MEMBER

    Yes it unbolts and comes off. If you still have the original block it isn't drilled for a starter you have to jump though that flaming hoop. If has a later block that is drilled for a starter that isn't an issue.

    If the block isn't drilled for a starter you will need and adapter like this that is available from several vendors. https://www.cl***icchevy.com/chevy-...08b374701ecf14b1bf062bd30eeeaf1a&gclsrc=3p.ds
     
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  4. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    327
     
  5. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Its a 327 out of a 68 Impala, appears to be drilled for starter, to stagger holes
     
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 35,977

    Mr48chev
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    That solves the issue I mentioned above, you just need the correct starter to match the tooth count on the flex plate you use with the 327.

    I
     
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  7. Budget36
    Joined: Nov 29, 2014
    Posts: 15,303

    Budget36
    Member

    Not 100% sure, but I’d guess the TH350 would be longer than you PG is. I have one of those PG plates, I recall it’s about 3 inches think? You might be in good shape.
    Check the length of both of them and see what you are up against
     
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  8. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
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    So the same flexplate will work?
     
  9. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Yep 3". I got the 350 with the 6" tail suppose to be same length as power glide. When I put a tape on the glide it was 27+ inches
     
  10. jimmy six
    Joined: Mar 21, 2006
    Posts: 17,062

    jimmy six
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    You loose the 55 bell housing/trans side mounts and gain a rear mount. . there are mount brackets for dirt track engine that use the trans to engine bolting. I’ve used them for years with Ford donuts. A new cross under will need to be fabricated or you can get one for the rear of the trans. Some don’t like the front mounts on a 55-57 with a rear trans mount but I’ve never had a problem with that set up.
     
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  11. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    So when I remove the 3" piece won't that change my driveshaft length and transmission mounts
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 59,931

    squirrel
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    the later powerglides are longer, you might need to get the drive shaft shortened...it will have the wrong spline yoke, also. Make sure you have a kickdown cable, add the vacuum line, and reroute the cooler lines, and get a decent shifter linkage on it.

    Should have the big flexplate, and take the normal 327/350 stagger bolt starter.
     
  13. Budget36
    Joined: Nov 29, 2014
    Posts: 15,303

    Budget36
    Member

    Measure your end of tail shaft to engine mount(not to adapter) but to the block. Then measure the front of the TH350 to the end of the tail shaft. The TH350 bolts to the block without an adapter.
    Your next thing would be to verify the spline count/ect on the output shafts. They may be different, so you may need to change it on the driveline anyway
     
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  14. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Have a 27 spline yoke for transmission end of driveshaft, suppose to be right for 350
     
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  15. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    My power glide is 27 1/2" approximant. suppose to be same as 350 with 6" tail. I wondering if when I remove the 3" piece between the power glide and engine if I won't have to lengthen the drive shaft. I have the 27 spline yoke now to change from power glide yoke. .
     
  16. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Was planning on using these mounts as long as I have the front motor mounts, but maybe won't work when I take the 3" piece out
     

    Attached Files:

  17. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
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    OK Re- read the 350 length compensates for the 3" filler
     
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  18. Budget36
    Joined: Nov 29, 2014
    Posts: 15,303

    Budget36
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    good deal
     
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  19. Blues4U
    Joined: Oct 1, 2015
    Posts: 8,068

    Blues4U
    Member
    from So Cal

    Is the engine mounted with front mounts or side mounts? Those bell housing mounts are meant to be used with front engine mounts, not side mounts. If the engine has side mounts, I think you should use a tailhousing transmission mount at the crossmember.
     
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  20. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Engine has the front mounts
     
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  21. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    New transmission arrived. The 350 is 27 9/16". The power glide best I can measure is 27 1/2", so its a wash basically the same. That being said The starter plate between the power glide and engine is 1 1/2 " so once I remove it and mount the 350 directly to the engine I will at least have to lengthen the drive shaft 1 1/2"
     
  22. Mr48chev
    Joined: Dec 28, 2007
    Posts: 35,977

    Mr48chev
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    NO you have to use the correct flexplate for that engine with a turbo 350 and the starter that fits the engine.. The flex plate for the cast iron glide won't work at all.

    You have to use the correct flex plate for the 327 and starter that bolts to it. a lot of small blocks are drilled for either a 153 tooth starter or a 168 tooth starter 153 being side by side and 168 being staggered. Some of the earlier ones weren't. Guys ran into that during engine swaps back in the 60's and 70's a lot.
     
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  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 24,516

    gimpyshotrods
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    You will need a transmission cross member under the tail housing.

    I have now had three people bring me cars to fix where the transmission case broke.
     
  24. Mr48chev
    Joined: Dec 28, 2007
    Posts: 35,977

    Mr48chev
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    Gimpyshotrods is right on that one, those side mounts do take the flex out at the bellhousing that happens when guys use the stock 55 mounts on the engine and a crossmember at the tail shaft and nothing in between. Either way you go hung in the air off those supports and not supported at the rear or hung of the stock engine mounts and the tail shaft mount you risk breaking the bellhousing and guys knock front pump seals out all too often with it only supported at the rear.
     
  25. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Why would this be different then the stock mounts now with front motor mounts, the conversion brackets from Danchuk mount to the same mount as stock
     
  26. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    Yes have the stagger starter holes in 327 block, so 168tooth
     
  27. PeggySue
    Joined: Sep 5, 2016
    Posts: 423

    PeggySue
    Member

    So are you saying both stock bell housing mount and tail mount??
     
  28. oldtom69
    Joined: Dec 6, 2009
    Posts: 583

    oldtom69
    Member
    from grandin nd

    typed a long step by step post to explain all the steps and deleted it-where in northern MN are you??would be easier to drive there and show you! you will no longer have a place to bolt side mounts to-driveshaft length should be OK,but no one has mentioned you will need a different spline front yolk motor mounts aren't a problem,safe,reliable mounts are!
     
  29. gimpyshotrods
    Joined: May 20, 2009
    Posts: 24,516

    gimpyshotrods
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    What is the case of your current Powerglide made of.

    What is the case of a TH350 made of?

    Which is stronger?
     
  30. gimpyshotrods
    Joined: May 20, 2009
    Posts: 24,516

    gimpyshotrods
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    If front mounts are used, I would use the side mounts, and a proper transmission crossmember, if you have anything more powerful than a 265.
     
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