I am in the middle of a DRM brake bias spring install which has so far been a piece of cake. I didn't even have to remove the master cylinder from the car!

Anyways, I used a snap ring puller to remove the old spring retainer, took out the old spring, and reinstalled the new spring in to the proportioning piston / combination piston which comes out of the end of the master cylinder.

On the proportioning piston/combination piston I noticed 2 small 1/16" (approximately) holes. These 2 are in a line with each other, one towards the back of the piston (closer to firewall), the other towards the front (towards the front of the car). There is also a 3rd 1/16" (approximately) hole on the combination piston. This would be in the 9 o'clock position if the other two holes were in the 6 o'clock position.

I am pretty sure the 2 holes in a line with each other need to be installed on either the 12 o'clock, or 6 o'clock position. Basically, I don't want to install this piston upside down.

Does anybody know whether these 2 holes need to be up (towards master cylinder reservoir ), or down (towards bottom of car) when reinstalling this piston?

Any help would be appreciated...BTW my Chilton's manual talks about reinstalling the proportioning piston/ combination piston back into the master cylinder, but does not show/ explain these 2 holes.

Thanks!
Dave