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I recieved a spare "rebuilt" top end with my TR6R that was also "rebuilt"(thats the one with the junk guides,that i had to replace ) so i decided to take a look, the rings were upside down on one piston but i miked the barrel and the piston, good clearances. any way the casting # inside the pistons read, 6980 413 ALCAN then 7622-1A. who makes these? they are indeed new. the rings stated STD. and according to my measurements they are(although upside down and gapped wrong!).just curious if these are NOS or some Asian replacements? one last question. I didnt see any forward noting marks, are these pistons reversible? usually there is an arrow or dot indicating PTO side or forward for placement. just curious.
 

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Check the size of the valve relief cutouts in the tops of the pistons. Mine had one cut out slightly larger than the other so I installed that on the intake side.
 
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