Re: Master cylinder BM-57. I have one of these factory fitted on the Z. It is marked BM-57 NISSAN NABCO JAPAN. The vehicle is ABS equipped & the pipe work connects to the front two connections on the engine side of the cylinder. The rear connection port is plugged. There is also a plug in the centre of the cylinder on the opposite side. Nissan FAST lists this cylinder as a Twin Turbo part number 46010-40P02 from 09/1993 up to 01/1997. There is also an alternate part number available, it is 46010-40P22 it is suitable for Twin Turbo's from 07/1989 through to 10/1998. The bore size is listed as 17/16", which should be listed a 1-1/16". There is no reference to the Non Turbo under the above part numbers.
Looking to discuss this some more. I'm coming across more and more evidence to suggest that once you match the bore sizes, ABS and non ABS masters function the same - the former simply having one port blocked. Numerous reports from the Skyline boys state that they delete their ABS and either simply T off the front line to the two calipers, get the unused port working and the bias stayed the same. One bloke said he spoke to multiple brake shops and they all said the ABS only modulated wheels locking up - not bias. I've also heard that there is different bias between chassis', and also that one can pop open their BMC and change the proportioning valve to adjust this. Which port is blocked on the three port ABS cars seems to depend on the chassis - I think R32s use the middle port. There's a Jap mob who make after market BMC's for people with massive stompers (like me) on their GTRs but the only ones I seem to be able to come across second hand (new is dear as ****) state that the unit was fitted to a non-ABS car. The company also requests ABS or non upon ordering - though I have no idea if that simply determines whether they wind in a tidy stopper to the unused port.
How many of them actually have a clue how to set up a race car though? (Note: I definitely don't but I'm at least aware it's a skill I lack so treat relevant mods with caution) and just because they don't notice it day-to-day doesn't mean the difference wont be there when it counts. That said, the early Z has the most rear-biased brakes I'm aware of in a nissan and front biased is safer and more controlled in most situations so you're unlikely to be going the wrong way by swapping out a standard Z BM57. I point it out more as a due-disclosure thing than something that will absolutely ruin the car, people should be aware of the potential changes and make sure they get to know the feel of the car after the change. You're right the ABS in our cars doesn't control bias (I think I corrected myself on that in another thread) but it does compensate for it; without ABS a super rear biased car will quickly lock the rears and put the tail around, with ABS you can apply strong braking to the rear up until they begin locking when the ABS should step in and prevent you losing control. Without ABS or a talented driver emergency stopping in a rear biased car is going to be messy. Brake pads can make a big difference in bias too though so in our rusty old nissans maybe I'm being too pedantic. As for swapping bias valves between MCs czp list different kits for the Tokico and Nabco so parts may not be interchangeable, same for any aftermarket unit, they do the same job but internal components may not fit in other castings so finding the valve you need/want may not be easy.
You're right, I'm sure most guys don't know their head from their ass when it comes to this stuff. There are however a few very talented people over that way, and with so many separate discussions I came across nobody was ever shot down (some of them even wrote in full sentences). I'm keeping ABS, and will have a massive rear bias overload. I want to fit the after market master cylinder to make up some fluid volume, and an adjustable proportioning valve to control bias - then go out to a skid pan day and set it up right. If it were up to me the master itself wouldn't have proportioning in it (if viable).
