I was given two engine rotor from a friend. He said they are S5 TII rotors. After i started looking at them they seemed like S4 rotors. They are cast in the chamfers not a machined look like the S5 rotors. How can i tell if they are S4 TII? I have a S4 N/A rotor here and starting looking for anything different bettween them. Only thing i notice is the chamfer on the rotors three faces and the rotors in question are alot narrower than the S4 N/A one. So I'm leaning that they are S4 TII rotors. How can i confirm this.. I weight it at 10.2 lbs also.. Thanks for any info..

If they are narrower, they are 12a rotors. And by the weight/description, they are 76-82 12a rotors.

theres a thread in the faq. but basically if its got a cast combustion recess its pre 89. if its 3mm seal its pre 86, and if the rotor is narrower its a 12a

The chamfer in the picture is narrower not the rotor..

https://www.nopistons.com/forums/index.php?...hl=rotors&st=25



scroll down a bit https://www.nopistons.com/forums/pub...#>/biggrin.png