..link to a thread a started in race car tech forum. apparently no one knew the answer.

https://www.rx7club.com/forum/showth...41#post2068341

 

SA housings have larger exhaust ports than FB' engines.

 

Excellent!

Now if I only had the lighter '84-'85 rotors!

 

If rules allow this is the setup:

79-80 Fed. Rotor housings - biggest exhaust
81-82 flywheel and front counter weight - lightest flyw.
83-85 rotors. - lightest rotors

Of course the motor will have to be un-assembled and rebalanced prior to being rebuilt.

John

 

How much hp would this 12A setup make over any other 12A setup assuming everything else (carb, exhaust) are the same? Noticeable?

 

From the dyno work I saw it was 4-6 hp at the rear wheels, what you really gain is the ability to rev the engine faster and run at higher RPM.


John

 

Be careful, this would NOT be legal for SCCA CSP or ITA/IT7 cars. Remember, you can only update/backdate entire assemblies, no mixing and matching.

 

Yeah, any frankenstien cars land you in MOD class, where you compete against kit cars and the like.

 

haha I know Carl, I'm not plannin on doing this. But after the class tech at MARRS 1, one guy was found with SA housings and was said to be illegal. I was just wondering

 

Oh I didnt think you were, just givin a heads up to all. I asked about using 83-85 rotors and 81-82 FW/cw to see what had to be done to make it work (for my street car). That was on the IT forum. I got into a flame war cause someone mis interpreted what I said, and I mis understood their response LOL. It happens, Ive learned my lesson not to read too much into what people say.

 

When I ran Pro7 in NASA it was legal to do the swapping of parts, otherwise the were going to be breaking into a lot of motors. Hard to tell if somebody is running a light flywheel with light rotors, unless of course you are SuperMan.

John

 

That kills me. NASA doesnt police engine parts, but they police air bleeds? SCCA allows only assemblies to be swapped. And get this, it depends who you ask to say what an assembly is. Mazda says since the engines are sold w/o a FW, then its not part of the engine "assembly" to them. But ask an SCCA tech guy what he thinks. This info is what I think lit the fire of the flame war.

Also, isint it hard to tell if someone massaged their ports a little? Ive heard for years about that happening, true or not? I dunno.

 

I'd use the '81-82 flywheel with the rest of the '83-85 rotating assembly. Saves rebalancing since only the flywheel needs to be re-balanced. If you use a '79-82 front counterweight with '83-85 rotors it will need rebalanced as well.

 

Well, I was under the impression that light flywheels are legal in CSP...

14.10.L: Any metal clutch assembly, metal flywheel, or metal torque converter that uses the standard attachment to the crankshaft may be used...

but then, I read this...

14.10.P: Rotating and reciprocating parts may be balanced but not lightened.

That sucks.