The grooves are a good idea, but it looks like the top groove was too high. Maybe a design error, maybe a machining error. I don't really know without seeing them. Sometimes pictures don't show everything.
I believe the pistons I have are just an older version of this one from 440source. This discussion now has me a bit curious....I am certainly not a professional engine builder, and have never had an engine assembled in my garage on a dyno. Due to covid parts shortages I have a not very good combination in my car: 440 +0.032 (yes...32 over) with very old style L2295F30 TRW pistons, LY rods, 75 cc Performer RPM heads, a Hughes "real 6 pack" cam, performer 440 intake (fits under a flat e body hood) and iron hp manifolds. It has sky high cranking compression, but I think it would probably be safe on an engine dyno up to 6000 rpm with 112 octane fuel and conservative timing.
If I can find a dyno around West Palm that would put up with my nonsense it would be amusing to make 3 pulls with this not so great ~12.1:1 440, then go home and put the same heads, intake, carb, exhaust manifolds, and cam onto this ~9.8:1 CR 493 with the 'hate' pistons and run it again on the same dyno to compare the results... does ~10% increase in displacement overcome ~20% lower static static compression ratio?
