I purchased a 93 Si a few months back and noticed it has a Wilwood proportioning valve by the master cyl. I had a problem woth my rear brakes wearing very fast and had alot of brake dust with ceramic pads. I haven't driven the car since I found this but I did turn it all the way down.( It was turned all the way up). What exactly does this thing do? And could this be the problem for my rear pads wearing fast?

 

Proportioning valve controls how much fluid and pressure bias there is between the front and the rear brake sets. The size of the valve is dependent on the size of the pistons, and the travel the piston has in each wheel. Most civics use disc front and drum rear, so most of the stopping power is in the front, therefor it has forward biased brakes. Im guessing yours is adjustable. By itself it is worthless, but with bigger brakes you will need a different prop valve. (the reason with with rear disc brake swaps you need a different proportioning valve, different bias front to rear)