What Master cyl and booster to run with Cobra calipers?

[cdk4219]

I am in the process of installing brakes from an '03 Cobra (front and rear) on the 260z, and wondered what the best solution for the master cylinder and brake booster were. I searched and the 280zx 15/16" with booster have come up for a bolt in. Are there some other options that I am overlooking so that i can have a good pedal feel. Thanks Chris.

[MrFancypants]

The early 280ZX MC is the only one that is drop in for you. Unfortunately the early Datsuns have a vertical mount rather than a horizontal mount like all later Nissans do. If you want to try any other MC, you'll also have to get the matching booster and make the necessary modifications to make it work.

 

I would have gone with the 280ZX MC myself but the booster in my 260Z was cheesed. It looked like there was a major brake fluid leak that ruined it. Rather than bother with getting a rebuilt booster, I am retrofitting a booster/MC from a 99 Infiniti G20. The mounting bolts for the booster are different.

 

From what Ive seen, any modern passenger car that weighs close to 3000 lb is going to have a 15/16" MC.

 

 

 

- Greg -

[blueovalz]

I don't have a set of Cobra calipers in front of me, but I believe that when I measured the diameter of the pistons, I found that they were comparable to the piston area of the OEM Z. With that said you may want to:

 

1) Use the OEM master cylinder (avoid going to a larger ZX master cylinder) to maintain the OEM feel. Or...

2) Measure the OEM caliper piston bore (one side only and don't depend on the exposed portion of the piston being the correct diameter at the bore) and compare that value with the combined area of the pistons (bores) on the Cobra.

 

Doing this will let you know what changes are needed to maintain a factory feel at the pedal.

[cdk4219]

Do you think that it will make a difference that I have changed the rear to disc brakes as well? I plan on installing an adjustable proportioning valve, and possibly hydraulic parking brake in the system.

[blueovalz]

This may have some effect on the feel. I believe that the mechanical advantage is greater with the drum brakes verses the comparable disc brakes based upon cylinder size and the fact that pressure is being applied to only one end of the brake shoe. This then would indicate to me that a larger MC is not needed with this conversion. Weigh that with the fact that the rear brakes contribute a smaller fraction of the stopping force when compared to the front brakes, which may also need the smaller MC advantage. I don't think you could go wrong either way (Z or ZX MC), but I don't see the need for the larger MC with the components you've described. Just some considerations to muck up your thought process.

[cdk4219]

No mucking up whatsoever. I did a 90 BMW 318is 302 (5.0 T60 turbo FI) swap a couple of years ago, and had to get a different (smaller) booster and different size MC from a Geo Metro. It works, but the pedal pressure is much greater than I like. Just dont want to make the same mistake on the Z.

[DavyZ]

I did a 90 BMW 318is 302 (5.0 T60 turbo FI) swap a couple of years ago,..

 

You are free to post pictures of that or provide a link--it's something a number of us would like to see

 

Davy