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Thread: dumb question about flex plates

  1. #1
    I never thought about this much but is there a front and back to a flex plate? Looking at the stock one I have in the garage, the ring gear appears to be centered.
    The reason this question has come up is, my engine apparently originally came with a top mounted starter. When I bought the boat, there was a starter mounted on the bottom. I went ahead and changed out the starter with a mini high torque and also installed a new SFI flex plate the same way the other one came off.
    At the end of last year, I had an issue with starting the seemed the flex plate was warped. Last night, I was able to get the flex plate pretty straight but the starter was still disengaging so I swapped it out with another.
    To back step a little, with the flex plate being a bit warped, the starter would disengage after about a 1/2 turn of the flex plate. With the new starter and straightened plate, all seems good.....for now.

  2. #2
    oh yea, the reason I ask is I want to go back to the top mounted starter and was wondering if I need to turn the flex plate around?

  3. #3
    Mighty Thor
    I can't speak for all flex plates, but on every chevy I can recall and Most fords I have seen there is a front and a back on the chevy the easy way to tell is the center hole has a slight lip that faces away from the engine. If you put it on backwards the plate won't sit flat on the crankshaft. Seems to me there is also a slight difference in the bolt holes that Is designed to keep them tight but I could be wrong on this. If my memory serves me, on the last ford I did it would only go on one way because the bolt holes would only line up in a certain orientation. Again, I could be wrong.

  4. #4
    Senior Member
    Join Date
    Apr 2010
    Like Thor said, the BBFs definitely only go on one way. I can't remember the bolt pattern being off (although he's probably right) however, I seem to remember that it'll rub the block if installed backwards.

  5. #5
    I guess I could have clarified that a bit more. The new SFI I put on didn't have the lip on the big center punch out like the stock plates. I put the new one on in the same direction which I assume is correct for the stock starter location.
    Would a different flex plate be needed for the top mount starter? or maybe a little different location for the ring gear? Or is this all a mute point and the top mount starter will bolt right up without any issues?

  6. #6
    Senior Member
    Join Date
    Feb 2009
    Steve, if the flexplate you have has a chamfer on one face of the ring gear teeth, that side should face the engine. If the torque converter holes are on a raised boss, the raised side should be away from the engine. Of course an aftermarket flexplate may not have either of these. Mine was flat, But all the SFI markings were on the side that faced away from the engine.
    The topmount starter should work with a standard diameter flywheel/flexplate, which for most BBC is 14". I think flywheel ring gears with the appropriate tooth chamfer were available at one time.........

  7. #7
    the flexplate will work with either top mount/reverse drive, or a standard location starter, ...Vic

  8. #8
    Wicked Performance Boats
    The reason original equipment flex plates wobble is, that they are thin and must be bolted to a torque converter to straighten them out. Once you go to an sfi flex plate, they are about .060 thicker and run truer. Top starter should work also. Budlight

  9. #9
    Mighty Thor
    Yep, if you have the right # of teeth on the flex plate (ie same diameter) then starter will work right. That is the nice thing about starter gearing they don't change tooth size so same # of teeth = same diameter.

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