A friend of mine, Joe, mentioned to me that when using a rear counterweight on the S5s, the counterweight designation doesn't matter, as long as it's S5 and up (less RX8). S5 N/A, S5 TII, FD3S, all work and balance on the same motor.





Is this true? I thought the different compression numbers affected the weight of the rotors slightly, requiring a different CW? Are they all balanced to the exact same weight or what?



Is there any other series of 13B engines that you can do the same thing to?

74-85 13B are the same



86-88 13B are the same



74-82 12A



83-85 12A



89-2003 13B



and the rx8 stuff



the 3 and 4 rotors are different

Yeah Colin, so when are ya going to come pick one up? lol

Um soon!

Haha whenever man, I just saw this thread and had to reply.

what's the difference between manual and automatic counterweights?

There are no manual counterweights, per se. The counterweight is part of the stock flywheel. When you upgrade to an aftermarket flywheel, you need to use an auto counterweight since those flywheels dont have built in counterweights. Also, aftermarket flywheels are designed to bolt to the auto counterweight.

so if i wanted to get an auto cw for my '85 13b, would i just try and find one from the same generation or would i have to have the whole rotating assembly rebalanced?

either one. much simpler to find the 1757 part number, from a 74-85 13B