Flexplate/pto question
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Flexplate/pto question

  1. #1
    Senior Member H20MOFO's Avatar
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    Default Flexplate/pto question

    Long story short my driveline pto bottoms out on the crank before it clamps onto the plexplate, I could throw it onto by bench/belt sander and make it fit. I'd have to shave off prox 1/16". My old motor was internally balanced and this one isn't, is there a difference between a pto hub that's for a internally balanced motor and external? Right by my index finger there is a bolt hole between 2 others, on my old crank there were no threads into the crank on that hole , but on this crank there are threads there. I think I'm having one of those " there's your sign" moments. lol
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    Senior Member moneysucker's Avatar
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    Looks like that pto is made for flywheel not a flex plate. My guess is that you could either make a spacer or hit that thing with a grinder followed by a belt sander.
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    Senior Member Oldsquirt's Avatar
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    There are different PTOs for flexplate and flywheel, doesn't matter about internal or external balance. Show a pic of the crank side of PTO as well as a shot of the end of crank. Doesn't happen to be a pilot bushing in the end of the crank, by chance? You do have the dowel pin holes lined up properly, right?
    Last edited by Oldsquirt; 11-15-2008 at 01:30 PM.

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    Senior Member H20MOFO's Avatar
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    Thanks Cy and Oldsquirt, I can definatley make it fit. I guess my biggest Q at this point is should I put a bolt in the hole that is at 12:00 on the pto photo, and at 9:00 on the crank photo. It wouldnt be doing much good other than 4 balance because the bolt will fall right through the pto piece. My old crank didn't have threads under this hole but my new one does. There is no dowel on this crank??
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    Cantard 71hallett's Avatar
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    That extra hole just stays empty. Fire up the grinder.
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    Senior Member H20MOFO's Avatar
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    Thanks all, she fits now.
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    Senior Member ol guy's Avatar
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    Quote Originally Posted by moneysucker View Post
    Looks like that pto is made for flywheel not a flex plate. My guess is that you could either make a spacer or hit that thing with a grinder followed by a belt sander.
    Moneysucker nailed that one! that D/S adapter is for a THICKER flywheel and with a flex plate that will bottom in the crankshaft before it seats properly. For what its worth make sure you have end play when the d/s bolts up. If its to tight your'e motor will have rear main bearing for breakfast. M

  10. #8
    Senior Member H20MOFO's Avatar
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    FWIW I had the same dl adapter on a flexplate with a different motor, no problem. As far as the pto/adapter style how does it differ?? If mine is for a flywheel not a flexplate?
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  11. #9
    Senior Member ol guy's Avatar
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    Quote Originally Posted by H20MOFO View Post
    FWIW I had the same dl adapter on a flexplate with a different motor, no problem. As far as the pto/adapter style how does it differ?? If mine is for a flywheel not a flexplate?
    thickness of a flywheel or flexplate. I'm sure you already know that! M

  12. #10
    No Sandbar To Far sanger rat's Avatar
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    Put a washer on that socket head back there. Looks like it would slip right through that chain.
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    The only blab's I will even be a part of is just when it is me they are talking about. Aaaah yes I can see a few good looking shiny tall deck motors on the beach, with barely enough fuel to get back to the launch saying, "Holy crap how fast you think that Daytona was going man? That's like the 20th time he's gone by today?"

  13. #11
    Senior Member Oldsquirt's Avatar
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    Quote Originally Posted by H20MOFO View Post
    As far as the pto/adapter style how does it differ?? If mine is for a flywheel not a flexplate?
    A flexplate PTO will "register" inside the end of the crank and have a slight recess where the raised edge around the flexplate center hole will be. Some of the later flexplate PTO may not have a stub that registers inside the crank.The flexplate PTO that I have used for a Chevy had a stub that registered in the inner part of crank (where a pilot bushing would go if it were for a manual trans).
    A flywheel PTO will "register" to the inside of the flywheel center hole with a lip.
    Your PTO does appear to be for a flexplate. It also looks pretty old.

    Those "extra" holes you are asking about are for a dowel that is used to properly align the flexplate to the crank. This is important for an externally balanced engine as the extra balance weight on the flywheel/flexplate needs to be correctly oriented to the crank.The only reason I can think of for that hole in the crank being threaded is that it is an aftermarket crank(this is your big inch stroker motor, right?) and may have been intended to have a dowel that threads into the flange(just an educated guess ). Stock GM dowel was just a split roll pin. If this is, indeed, an externally balanced engine, you MUST install the flexplate with its "extra" hole lined up with the matching hole in the crank.

  14. #12
    Senior Member H20MOFO's Avatar
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    Thanks Oldsquirt, again. As far as the motor, it's a stroker. And as far as the adapter being old , it's probably the only orig part I have left off my tahiti, so maybe 1977 ish? Thanks again all, I went through so much fun with the whole internal/external deal, I just thought I'd check.
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