Can anyone clarify for me what the timing marks are on the 12A pulley? I saw some info indicating that the first mark( supposedly yellow a few decades ago ) is at tdc and some info ndicating that the first mark is 5 degrees after tdc. Are there differences between years? Different market models? Mine is 84, us model, if that makes a difference. As I am in a process of converting to run megasquirt and turbocharging, it is somewhat crucial to have the timing right, those 5 degrees could mean trashed engine.
Thanks for the help!

 

The timing marks on all 12A's are the same.

 

From reading some old threads and manuals I am not sure. May haynes says it is a TDC on older models, then in the revision for newer models section it lists 5deg atdc for uk only models, no mention what it is on US models, which is extremely useful...
I read some thread from some ausie forum discussing that pre 83 it was at 0 degree, after that 5 degree atdc.
I just looked in the FSM online here --> Foxed.ca - Mazda RX-7 Manuals
The FSM says says that the mark is at 0 degree. Yet some other older threads on this forum I read it is at 5atdc
So I still don't know what it actually is, this is frustrating, it is a critical piece of information for an engine, should not be so obscure..

 

I've done some reading on this based on what you have posted and it does sound like depending on year of pulley, the degrees can be different.

 

so, I have been looking some more at the FSMs, I see this:
1980 model:
leading 0degATDC
trailing 20degATDC

1985 model
leading 12A 0degATDC
13B 5degATDC
trailing both 20deg ATDC
I have no Idea why are so many folks adamant about the 12A having leading timing mark at 5ATDC. Seems like that's a spec related to 13B. I wonder where this info came from? should the factory manual not be trusted for some reason?