DriveFast7

iTrader: (1)

Santa Claus came early this year.

New 89-91 high comp rotors arrived at my doorstep today. On the side of each rotor, the letter S is stamped on each side. Six S's per rotor. What does that mean?

And...how do I determine if this is a matched and balanced pair of rotors? I'm used to pre-86 engines which have the letters A, B, C, D stamped on them signifying their weight. Does 89 rotors do something similar?

farberio

iTrader: (7)

The S5 rotors use the same A,B,C...etc stamping as S4. As far as I know at least.

K-Tune

iTrader: (26)

the ABCD is still used. just confirming :]

RotaryEvolution

iTrader: (30)

they should still have an A-F stamp on them, ignore the S stamps along with all the japanese symbols, they are insignificant.

DriveFast7

iTrader: (1)

Thanks Karack. Last night I inspected a 74 13b, 81 12a, and 89 13b rotor and they all had the weight stamping on the same spot. The gear side, to the right of the bearing alignment tab.

RotaryEvolution

iTrader: (30)

wierd that they aren't stamped, does it show any signs that someone removed the stamps? i have yet to see any rotors that do not have a weight designation stamp.

only thing i can suggest is send them off to be balanced with the whole rotating assembly. you can use them without any balance stamps but if they are far enough apart then excessive stat gear bear wear will result.