info on starter mating problems 74 vette, 383 emgine, 400 xmsn

Here's more food for thought:

You said the flex plate is new, seems like that could be a likely suspect... also, it's not clear to me whether the orig "Each starter lasts 3 or 4 starts, makes terrible grinding noises, and now there is a few metal slivers on the ring gear. When a freind starts car and I observe starter it seems that drive comes out OK, but when extended, it does not make contact with ring gear, barely touches it, etc."

- Exactly what happens... does the starter gear stop when it contacts the ring gear, or does it overlap the ring gear teeth (fore & aft) but is just a bit too far outside the ring gear circle diameter, or does it engage fine but slip when it tries to turn the flex plate, ...or what?

The chart I referenced in a prior post mentions 12.75 and 14 inch OD flex plates. Is it possible you have a 12.75 inch plate and should have the 14 inch for your engine? Looks like either size might bolt up, even if not the proper outside diameter. In my old circa '76 parts book, all

66-76 Corvettes with automatic take the same heat/cold-shrink-fitted ring gear #3991408 (which is still in the parts system), so they were all pretty common... unfortunately I am not certain which OD size that is; the only flex plate I have sitting around is from an 84 Vette (which had a 700R4 tranny) and the OD measures 12.75 inches tooth-end to tooth-end... I do not know the size for a TH350 or TH400, but my guess is that it's 14 inches. Years ago when I swapped out the engine in a 71 car (not a Vette) for the 84 engine, I had to use the old flex plate for the TH400 tranny in that car... I can't remember why but it could have been the diameter.

- has this engine ever actually started, or not? "Terrible grinding noises" aren't necessarily the fault of the starter, but could be an incorrect (head too tall) or a loose flex plate bolt, for example, or even an engine too tight to be turned by the starter... can you see the damage on anything? (ie, exactly which parts are those metal slivers being removed from?)

- Is there any possibility that there are chamfers on ends of the ring gear teeth only on one end/side of the flex plate, or is the ring gear offset slightly from the flex plate mounting surface, thereby placing the ring gear teeth too far away from the starter... ie, was the flex plate somehow installed backwards? (wild speculation on my part, I don't even know if that's possible)

As flyboyf102 so eloquently stated:

Did you install the starter to engine bracket? I had a 350 that ate starters until one day I was told to actually USE the bracket. I did and that was the end of eating starters.