I'm building a FD engine for my SA. I purchased a set of 3mm FD rotors from different people. One rotor has a new bearing installed with 1200 miles and the other rotor don't have a bearing installed. Should i just order the pair? (I have all the bearing tools). Also the stationary gear bearings are good.. Should i just change all 4? Thanks..

If it were mine I would start off with all new bearing. You have the tools so you don't need them. DO you have the money for the bearing? If so I would say go for it - It is easy to replace them now as opposed to if the god bad after the engine is all assembled. Not that 1200 miles is a lot, but it is just easy at the moment!

Yea I'm gonna order all four bearings today. Don't want any issues later..

I would measure them first before doing anything.

I second that, why buy/install new bearings if they are in spec?

I pulled this off the CLUB: new vs used bearing CMM scan



Now obviously this is just one used bearing, but you get the idea...



http://www.mazdatruckin.com/images/RotorBearing.jpg



p.s. Don't mind where the seam is on the used bearing, this was done with the bearing still in the rotor too...

Measure it one way then perpendicular, measure your oil clearances as per fsm to see where its at. A lot of times, new bearings end up fitting worse than used ones, since people buy the wrong ones. With the fd/8 motors , you have to measure first, calculate then buy the correct bearing, going by colour alone is not correct, its just a starting point since Mazda uses the same colour for sometimes multiple sizes as well.

One rotor does not have a bearng installed. The other rotor bearing has 2000 miles.. Can i just install one rotor bearing and call it good after i measue the needed size?