Guest firebern Posted March 22, 2001 Share Posted March 22, 2001 I took off my datsun master cylinder and measured how deep it goes. It gave me an inch. Does the stroke depend on the cylinder diameter too? Cause a lot of you guys say that the master as to be replace. I ordered both the pulling and master, but if I could I would keep the the master I have, and exchange the new one for a new holley fuel pump(I couldn't get an MSD fast enough). Thanks, Fire. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 22, 2001 Share Posted March 22, 2001 Stroke is independent of the bore size. Stroke is more related to a volume issue and bore is related to the "mechanical leverage" issue of hydraulics. The ratio of the two (master/slave) should be about the same as OEM ratio, if you want the same "feel" at the pedal. If your slave bore is 20% larger area than the OEM piece, then you will want a master with about the same size larger too. If you were to leave the master the same (OEM) size, then your pedal will feel easier to push because of more leverage, but the stroke may not be long enough (not enough volume) to push the new slave piston the proper travel length to perform the work it was intended for. So the two must be considered together in the determination of a master, slave, or brake cylinder. Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 22, 2001 Share Posted March 22, 2001 As a starting point/to know what you want you first must know what you have. Especially if attempting to diagnose a faulty clutcvh master or slave cyl. I always check w/a flashlight the actual pedal travel (in inches) then jack up the car & slide under to measure the travel of the slave cyl. while someone else pushes in on the pedal. Once you have these two figures you then will have a better idea of what your ratio is between the two. Just because your pedal moves one inch doesnt mean you slave will move one inch. I once had to "Fabricate" w/help of friends a Clutch Master Cyl for an older car (An AMC) where there were no NEW units being sold. I was able to purchase a new unit close to the old unit but the ratio was incorrect; the unit bolted up but the length of the clutch master cyl's arm was too short/so I had to know what length to add to the slave cyl.arm by using the above mentioned process. After all/said/done...it worked out nicely. Just my .02c's worth & hope that helped. Kevin, (Yes,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 22, 2001 Share Posted March 22, 2001 Absolutely correct on that matter of the pedal length, because this ratio X bore ratios will give the ultimate advantage or leverage available. Another thing that is some times neglected is the pressure plate ratio when it comes to clutch system. A diaphram plate vs a finger type (not sure about the correct term hear) may require differing amounts of movement and/or pressure to release. If this is not taken into consideration, the bore ratios may be a moot point. So this muddies the water even more. This is why being lucky in picking the parts (my case) is better than skillful any day. This is why I like brakes. Bore to Bore, and in my case, ashes to ashes. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 23, 2001 Share Posted March 23, 2001 Good point on the pressure plate throw issue. The best thing to do of course, is to find a total combo that worked for someone else with the motor/trans you're doing that is happy with the pedal throw and force. Even with a bunch of calculations using some guidelines from McLeod in their instructions for their hydraulic TO bearing, I started with a M/C that was way to large in diameter, 1". (I still have that puppie - a short AP racing piece, if anyone is interested in it.) Then I went to a 7/8" and it was too large also (too much pedal force, not enough modulation) - at least I resold that one. Now I have a 3/4" and it seems about right. But this is for a GM diaphram pressure plate and the McLeod hyd TO bearing for a T5, so it's no germane to the Ford setup, necessarily. Experimentation is expensive! ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 23, 2001 Share Posted March 23, 2001 Terry, unfortuately, since we are typically going from American to Japanese cars with the drivetrain of the American car and the clutch pedal geometry of the Japanese, the master/slave cylinder bore ratio isn't enough information to really know what is going to happen as far as clutch engagement/disengagement capability (volume related) and pedal force. Many GM cars have a typcial 4:1 pedal ratio = (length from the pedal pivot to the pedal) --------------------------------------------- (length from the pedal pivot to the M/C rod attachment) On the 240Z, this ratio is about 6:1. So you must do a fluid volume and pedal force calc on the American car hydraulics in light of the pedal ratio for the car it's intended for and then use that same force and volume as a calculation starting point for the M/C stroke and bore needed. Unfortunately, the pedal ratio difference between the American cars and the Z drives the bore diameter up as far as required fluid volume moved while increasing the pedal force. It's been a while since I looked at this so I may be all wet. Regards, ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 23, 2001 Share Posted March 23, 2001 Pete I had to laugh when you described your experience in this situation. I too, felt a 1" was too large for the T/O bearing. So I tried a 7/8" brake master cylinder, and about pushed it through the firewall, so that's when I tried the 3/4", and the rest is history. Quote Link to comment Share on other sites More sharing options...
Trevor Posted March 23, 2001 Share Posted March 23, 2001 Thanks for the pedal ratio info, Pete. I was thinking of increasing the stroke by moving the cylinder down the firewall (use the bottom stock bolt hole for the top, drill new hole for the rod, etc.) and re-locating the rod on the pedal arm. Farther from the pivot = longer swing. But I guess the greater effort due to less leverage would defeat the advantage of a smaller diameter MC. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 24, 2001 Share Posted March 24, 2001 Actually, if you do that, you could try to duplicate the pedal ratio of the Mustang and you'd be in better shape with using any hydraulic parts that the Mustang might have used (I know nothing about Fords). Playing with the pedal ratio can help alleviate some of the problems with getting the right balance between fluid volume moved (getting enough to disengage the clutch) and pedal effort. Quote Link to comment Share on other sites More sharing options...
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