I have never managed to completely figure these damn things out!!

i did my due diligence and searched, so I understand that the correct counterweight depends on the rotating assembly, but what if I use rotors from one series and an eccentric shaft from another?

For example I plan to use the 89 NA rotors and either a GSL-SE or Rx-8 eccentric shaft, with a light steel flywheel.

I have read the Rx-8 eccentric is lighter so that would be my first choice.

I dont know which counter weight to use and I figure that I will have to have it balanced, but is that really necessary?

Would I be better off just to use the 89 eccentric?

 

Robert, I am going to say yes, you would need to have the entire rotating assembly balanced if using an Rx8 shaft. I would suggest speaking with Paul @ Mazmart. He can speak with Rick regarding the balancing and also quote you a price.


-billy

 

The counterweights must match the rotors. I have 89-91 NA rotors and bought 89-91 NA counterweights. I also use a Rx-8 shaft.

I do recommend getting it balanced, the balance shop added some weight the rear counterweight, and took a little off the front. It revs like a champ.

The 8 shaft is lighter but more importantly the rear half of the rear journal and the front half of the front journal are tapered smaller, about .0005". Keeps engine alive longer at higher rpms. And it is relatively cheap compared to all other shafts.

Be sure to check the rotor bearing clearances, especially if the rotors are used. I had NEW rotors and NEW Rx8 shaft and the rotor bearing clearances were .0032" to .0039".