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 original 74 engine was
rebuilt to be a 383, or if this is a new block.
You also said:
"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)
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