Tonight i was looking at all of my 12a parts just to see the difference in castings, and i noticed that all my housings and center plates have 17 bolt holes around the rotor chamber, but the end plates aren't tapped for the "extra" hole (right above the intake ports). I then noticed that my R5 ends have obvious casting spot that appear to just have never been tapped


has anyone ever drilled and tapped this and added and extra bolt?, or is it even worth it?

 

Yes i belive some 12A's had 19 tension bolts some had 17.not really sure never really looked at mine.

 

It depends on the year. 17, 18 or all 19. Mine pictured here only has 17.

 

I see your plate is also missing one of the top bolts. Which years came with the holes tapped all the way around? do the extra bolts offer any more protection from high rpm twisting or boost?