I have a GSL-SE rotating assembly with a bad rotor but a good flywheel. I want to use the flywheel on an older freshly rebuilt 4 port 13B with rotors from the '70s.

I noticed the front counterweights look different, yet the rotors are the same weight (according to Mazdatrix http://www.mazdatrix.com/faq/rotorwgt.htm ) and the same rear counterweight can be used. I just don't want to go through the hassle of having to pull the front cover back off in order to change front counterweights.

I just fired it up today with the heavy stock flywheel from an REPU and it ran nicely. I don't want to have to tear into it again just to swap flywheels...

The questions are:

1) Can I bolt the GSL-SE flywheel to an older 13B rotating assembly with 1757 stamped on the front counterweight?

2) Has anyone here ever done this? It's the flywheel with 304 on the back.

3) Or do I have to go through the trouble of pulling the front cover off to swap the counterweight over to the GSL-SE style?

Note: there were no automatic GSL-SEs, so no GSL-SE-specific rear counterwights are available. Everyone just uses the counterweights from automatic Cosmos etc.

 

You should do fine. Slight vibration on low-end maybe but thats all. Im using GSL-SE internals. I have tried aluminum flywheels, lightened steel, 215mm 21lbs stock flywheel then switched back to GSL-SE since heavier is better for weekend drag. honestly, I didnt even notice any vibration at all.

 

Cool. Yeah, my stockers have a slight vibration in the low end too, so if that's all there is, I'll be fine. It's probably more to do with oil sloshing at low RPM than a flywheel imbalance. Actually, the GSL-SE engine had an '86-'88 flywheel on it which caused no vibration but did wear out the stationary bearings.

Logically, if the '76-'85 rear counterweight can replace the GSL-SE or any other early 13B flywheel, I don't see why the GSL-SE flywheel couldn't be used with any early 13B front counterweight. I'll go ahead and try it. Thanks.

 

Here's a picture of the front counterweight. It sure is weird lookin'.