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Brake master cylinder upgrade....


Guest Twofortez

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Guest Twofortez

Looking to do the brake master cylinder upgrade since mine is leaking......the parts stores are closed so i grab an old Vic-Brit catalog for a little reference and they show two different brake masters for the 280zx....one for 79-81 and another for 82-83...which one should be used for my '73 240.......is just one of those 15/16's or what??

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I've done two of these swaps both on 71 series I cars. Both times I came away with way too much pedal travel. I noticed that the pushrod in the brake booster is a little shorter than a ZX pushrod. Has anyone else experienced this? What did you do to fix it? Thanks.

 

Joe

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I had to lengthen the pushrod on my 73's booster. It's a threaded end on a threaded rod. But very difficult to turn to adjust. I made it so there was a very little bit of clearance between the MC piston and the rod end.

My pedal throw is not long at all.

 

Thanks for bringing that up, Joe!

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Guest Twofortez

Thanks Pete......needed that info..........also found a braided line for the clutch slave cylinder somewhere......can't remember where i saw it......grrrrrrrrr....35 years old goin' on 75..hehe

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The tip of the booster rod is adjustable. It will have a hex shape on the tip so that it can be turned (you may have to grip the rod with a vise grip). I inserted a small screwdriver blade (that was roughly the size of the pushrod tip) into the MC and measured the amount of depth of the tapered hole (that the pushrod inserts into) to the mounting surface of the MC. Then I adjusted the booster pushrod that extends out past the MC mounting surface to this same number. You don't want to preload the MC when re-assembling the MC to the booster. I'm a perfectionist and did the assemble/disassemble routine a couple of times to ensure the rod was correctly spaced.

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Yeah I saw the rod was adjustable, but even when adjusted I could not get it as long as the 83 booster rod. Could the Series I cars have a shorter rod in the booster? I know the M/C is unique to those cars but I'm not sure about the booster.

 

Joe

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Guest Anonymous

I was having the problem of long pedal travel before brake operation with the 82 booster/mc and I have read to adjust the pushrod coming out of the booster to correct the problem. I have done that but the car isn't driveable for another week and then I'll test my adjustment. I did remember the brakes being overly sensitive like an 81zx that I used to own.

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Guest Anonymous

I've got an 82 booster and mc on my 76 and was wondering what the diff between the single and dual resevoir means? Also is the 82 mc 15/16's? Should I change back to a 76 booster and then the 79-81 mc? Thanks.

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I don't think I can address that problem. On all of my conversions I always used a Z booster with the ZX MC (because the 240 does not offer much room between the clutch MC and the side of the booster). If you are wanting to put a ZX MC on a ZX booster, I would then think that this would be a "bolt-on" operation with no need to change the pushrod length. All of the 280ZX MCs had a 15/16" bore. I've also used the single and dual reservoir MCs and found that other than the different bolt pattern (horizontal vs vertical) the bore size and operation is the same.

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Guest Twofortez

Swapped the new brake master cylinder (ZX) Sunday...believe it or not,I actually had to adjust the rod on the booster IN !!!!......sounded crazy to me too from the info everyone has shared with me.......works like a charm with about 4 inches total travel and no sloppiness whatsoever!!!! rockon.gif

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