500 flexplate differences

5one9

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What vehicle(s) do you drive?
2007 Magnum SRT8, 1957 F100
My engine came with a stock 'solid' 500 flexplate (from here on referred to as 'blue stocker').
I have another stock 'solid' 500 flexplate (from here on referred to as 'rusty stocker').

I drove the 'blue stocker' for a few months prior to pulling the engine to repair the leaky copper head gaskets. 'Blue stocker' worked ok with my mini high torque starter and had about 0.070"-0.080" of clearance between the teeth and the Bendix.
While the engine was out I decided to install an SFI flexplate. As I searched on Ebay I noticed two distinctly different looking SFI flexplate. One was very 'professional' looking, one was kind of 'cheesy' looking. Don't ask why I thought that, it was just my impression looking at the pics. One auction even had pics of both flexplates in their auction. So I ordered from the company that had only the 'professional' looking flexplate in their pics. That is exactly what I got. When it arrived it looked good and I threw the engine back in the car. Everything was bolted up and I hit the key and it sounded like S**t and I had to snap the throttle to get the Bendix to disengage. Under the car I went and added about 0.045" of shims to get it to work right. I also noticed that now I had more like 0.250" of clearance between the teeth and the Bendix. WTF? I started looking at the differences in the pics between the 'professional' looking and 'cheesy' looking flexplates and it looked like the 'cheesy' one was offset more like the stockers. When the rear seal started pouring on the engine I went ahead and bought a new 'cheesy' flexplate. When it arrived I measured it against the stockers and the offset was much closer. WTF#2?

Today I pulled the engine and here is what I found. Measurements were all taken from where the flexplate mates to the flywheel, to the edge of the ring gear on the Bendix side (the only relevant measurement since the thicknesses are different between stock and SFI. Also notice that the 'profession' looking flywheel is 1/16" bigger on the OD than any of the other 3.

I have included pics of the 'professional' and 'cheesy' flexplates for your ordering pleasure. I would steer clear of the 'professional' one although it may not matter with a stock starter. Oh, and the welds were much better on the 'cheesy' flexplate. All flexplates had 166 teeth.

FlywheelThicknnessODOffset
blue stocker0.090"13.88"0.412" (about 0.070"-0.080" from flywheel)
rusty stocker0.090"13.88"0.477" (I never installed this one)
1st sfi (# FLX50001)0.160"13.94"0.260" (way further away from flywheel)
2nd sfi (#FPHD500)0.160"13.88"0.395" (haven't installed yet)
 

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richie49

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5one9
Sometime back I had to replace my flexplate and if you look at most part houses They sell Pioneer flexplates. I found the pioneer flex from 3 different stores with different diameters. ( didn't measure them just went by the listing) The flexplate said made in mexico . Had to shave my starter mounting block down to get good clearance on the starter. I was too used to just throwing them on and being done on it,which works with the stock flywheel. I dont know about the sfi labeled flexplates but they are supposed to FIT. I would like to find a stock one to replace the pioneer one I have ,but havn't located one yet.I dont need it at the moment ,just want one for a spare if I need it.(the one I have on the engine should last pretty long time as the dang thing isnt running yet :rofl: :() It seems like people disigning parts for the caddy say thats good enough instead of checking it over before making them.
Richar richie49
 
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