Quick (possibly dumb) question:

My car is an '85 but the 12a is not original (don't know what it's from, but it doesn't have the tee on the rear iron water outlet). I've found different part numbers listed for earlier and later clutches, particularly a 8 7/16" and a 8 7/8" option. Measuring the clutch disk I took out, it's the smaller/earlier 8 7/16" - do I need to use the same (ala exedy 07020 or luk 07021, per rockauto) or can I use the 8 7/8" "normal" one (exedy 10008)? Flywheel appears to have room for the larger disk (measures 9" across inside the step), and I'll be getting it resurfaced so it'll be flat.

If I can use either, is there any reason to do one over the other? Any way to tell what year car my engine is out of (and what other differences that may make)?

 

There are 2 clutch disk and cover diameters used on our cars; 215mm and 225mm diameter. The 12a series use the 215mm diameter for each. The 13b variants (GSL-SE) use the 225mm clutch. Unless your engine has had the flywheel replaced - which would also alter the dynamic balance of the rotating assembly - if it's a 12a engine, it will use the 215mm parts.

 

If this is the case, then why does everywhere (include specialists like Atkins) list exedy 10008 (a 225mm clutch) for an '85 12a? There are tons of threads on here, even, where people discus exedy 10008 as being correct/OEM for their 12a.

 

79-82 12A = 215mm clutch disk
83-85 12A = 225mm clutch disk
Measure what you have.

NA 13Bs also use a 225mm clutch disk

here is a link to an old Mazdatrix page that has flywheel images. This should also help you ID what you need to buy http://web.archive.org/web/201607092...q/flywheel.htm

 

Cool, thanks (mine's 215mm, I measured again). From the pictures at that link, looks to be 81-82 which is good to know (and the lightest one there!). Finished the tear-down this evening (pulling the whole thing apart to change a dowel o-ring... clutch is a "while I'm at it" since the old one was getting thin) so once I finish inspections, I'll just order the 215mm (Exedy 07020) from rockauto (bummed that Atkins doesn't carry anything for the earlier ones, would rather support them!). Edit: I found the smaller one on Atkins' site, not sure why I couldn't earlier, but I'll get it from there.

Here's the picture I grabbed to send to my guy to make sure he could surface such a small, stepped flywheel (he's more of a big block sort of guy )

 

if you look at the rotors, the 78-82 rotors will just have a F or R stamp in the combustion recess, the 83-85 rotors will be NF or NR (the 12A turbo would be TF and TR).