I can actually answer this, as the same thing happened to me, I was
informed by Ken Gillanders (siq) ... once he quit laughing and go up
off the floor ... that those 4 ring pistons with one ring below the
wrist pin were ... TRACTOR pistons ... and were never designed to
exceed 2500 RPM for any length of time.
I replaced all of mine with Ken's piston/sleeve kit and have had
no further problems.
>I just pulled one of the old pistons out of my ailing motor. I was surprised
>to see below the three ring grooves (with rings in them) a fourth groove
>with no ring in it. This groove had holes drilled through the piston wall. I
>haven't seen anything like that in my manual or in the catalogs selling new
>replacement pistons. Whats up with that fourth groove?
1957 TR3 TS16765L
1970 TR6 CC59179L
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