Old Style Rotor Housings
 

To all,
I saw a picture of some old style (73-78) rotor housings and on two of them instead of a normal exhaust port it had a plug in it with three small holes. Does anyone know when these were used and why? It would seem to really interfere with the flow.

Also, I know that the 79/80 12A rotor housings are different from the 81-85 rotor housings. Does anyone here know what the differences are and why you can't use a 79/80 style thermal reactor exhaust system with an 81-85 rotor housing?

Just curious,
Peacedog

Here is what they look like...

i think they were from the european market.

the 81-85 housings dont have the xtra little port for the thermal reactor.

They were used in 12a twin distributor engines in rx2's. The '3 hole' exhaust ports flow pretty terribly however they make for a very quiet engine