Brake Master Cylinder
The above modifications made to my Z car, stop the car very well. Even though the new set-up stops very well, I had noticed a very slight increase in softness of the pedal, which after all, was expected due to the increase in piston area at each brake caliper from the OEM calipers. To remedy this situation, I began looking for a larger diameter master brake cylinder to firm up the brake pedal (but again, it still worked very well!). I found such a piece on the 280ZX's.
The OEM master brake cylinders used on all the Z's used the same 7/8" bore, duel reservoir cylinders, all with the same bolt pattern. In '79 the 280ZX went to a 15/16" bore, duel reservoir, which later changed to a single reservoir, maintaining the same bore.
On the early 280ZX cylinders, the cylinders look very much like the older versions, and the casting on the side is the only way to make certain they are of the 15/16" bore. The mounting method and bolt pattern used to attach this cylinder onto the brake booster is also the same as the older Z's, making this swap a pure "bolt-on" modification, with the exception of some slight re-alignment of the brake lines. Consequently, I used this set-up on my street Z, with wonderful results. Being very enthusiastic about now doing this on the racing Z, I looked for the exact same type of master cylinder for it, but found no "good" ones in the salvage yard (old, aluminum bore brake cylinders don't last long when moisture accumulates in them).
I then turned to the later 280ZX type of cylinders (remember; the single reservoir type). Unfortunately, these later ones have a slightly different bolt pattern, than do the earlier versions, but not enough to keep you from being able to use one. To mount one of these cylinders onto your Z, you must first remove the aluminum spacer used between the brake booster and the OEM Z master cylinder. This is because the latter style 280ZX cylinder bolt pattern does not use a vertically oriented bolt pattern like the older ones did, but instead, a horizontally oriented pattern. With this aluminum spacer removed, the studs on the brake booster that originally held the spacer on, will now hold the master cylinder on, without using the spacer anymore. Now, these horizontally aligned studs on the booster are just a tad bit too wide for the holes on the mounting flange of the master cylinder, so you must slightly elongate these holes slightly to allow the cylinder to fit onto the brake booster. To complete your modification, you must remove a small portion of the top stud of the vertically aligned studs on the booster (the ones that went through the aluminum spacer and that the original master cylinder used). This is because this stud will cause interference with the plastic fluid reservoir of the new cylinder when the cylinder is tightened down. Lastly, two small half circle notches must be filed into the mounting flange (at the top and bottom of the flange) of the new cylinder, to accommodate these vertically oriented studs. With the new master cylinder in place (without the previous aluminum spacer, and with the appropriate length adjustment of the brake push rod) you can put nuts on all four studs and tighten down. The two side nuts can be tightened normally, but the top and bottom nuts will not have a full seat to tighten down on (this is where you previously notched for stud clearance), so be careful here. I suppose no nuts are needed here anyway, but I feel "better safe than sorry". Again, as with the other type of 280ZX cylinder update, the brake lines will have to be moved slightly for realignment to the ports on the new cylinder.