Clutch master cylinder sizes...?

[distributorguy]

For those "in the know" were there different sized clutch master cylinders used in the cars/trucks that could be interchanged?  Planning ahead as I may need a larger displacement master cylinder due to less pedal travel in the race truck.  I know I can always change over to a Wilwood and get what I want, but a "stock replacement" could just bolt in and not turn into a 4-8 hour project.  Currently installed is a 5/8', but a 3/4 or 7/8 would make life easier.  

[Stoffregen Motorsports]

I think they were all the same size. Luckily, it's a pretty generic shape and mounting, so Wilwood should have something close.

 

How about moving the pedal pivot up?

[Stoffregen Motorsports]

This would probably work fine - http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Integral%20Reservoir%20Compact%20Master%20Cylinder

 

...or this - http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?group=Combination%20Remote%20Master%20Cylinder

[datzenmike]

I also think the master and all slaves are 3/4". I'll check.

Going to larger diameter master will only make the pedal harder to push and will over stroke the slave.

 

 

 

Roadster, 521, 510, 1200, B-210, 240/260 280Z, 610, 710, 810, 620 were the same, S10 and A10 had some same internal parts that match the previous 3/4"

 

After '80 and all 280zx, 720, 210, S110 had a diagonal mounting bolt pattern. And likely others. Probably the same 3/4" as they used the same flywheels and clutches, not much changed.

 

300zx, FWD Maxima, D21 Hardbody and S12 are 5/8"... maybe others.

[Stoffregen Motorsports]

He said his pedal travel has been limited, probably from floor mods or something. He can always limit the travel with a stop.

[distributorguy]

Exactly.  The wheel arch had to move inward toward the driver, and due to the extensive roll cage, the clutch pedal needed to move left a bit to allow enough foot room for safety.  We lost near an inch of pedal travel, so we need more fluid moving through the line via a larger master.  Who cares about pedal effort?  The driver is going to be so chock full of adrenaline that it could be a 600 lb pedal effort and it just won't matter.   :thumbup:   Realistically, we're talking about changing pedal effort from 90 lbs to 110-115.  

 

There isn't a lot of room to move pedal pivot points.  I've played with that many times in other vehicles.  This master may be fine.  We'll find out Thursday evening.  If not, I break out the Summit catalog.  Its only a 5/8" master.  Tiny.  This is all temporary anyway.  Until the other transmission goes in.  It just needs to be safe.  

[Stoffregen Motorsports]

What other transmission? You gonna run a Lenco!?

[distributorguy]

No, I found an alternative to the rare close ratio BRE 5 speed with a 1:1 5th gear.  Internal drag is nearly non-existent, with factory REM finished gears, and they are dirt cheap.  The main problem is that its a horrible fit, so I won't talk about it more until I'm bolting it to the motor.  If you look back through my land speed record post, its detailed there. Many obstacles to overcome before its a reality.  

[datzenmike]

There were three DD FS5C71B 5th gear transmissions from Nismo with various ratios 1, 2, 3 and 4th. Not that it matters as all 5ths were straight through.

 

 

Fit??? They should be the same length as any 71B so get the front drive shaft from any '74 and up 620. These are about 5.5" shorter for the longer transmission. Maybe you have a single length driveshaft?

[Stoffregen Motorsports]

Come on...don't leave me hanging like that!

[distributorguy]

Mike, you're still thinking inside the box.  

 

Most Nismo gear boxes had an overdrive 5th, but not all.  The Z-car setting records at Bonneville and all over the US has one of those special boxes from Bob Sharp.  The one I have in mind has less internal drag - by half.  Less parasitic loss + less weight + 1:1 5th gear = faster top speed.   Plus it was free, and I can get as many as I want at $300 each.  Some things are better left not talked about.   :ninja:

[Stoffregen Motorsports]

Bastard.

[distributorguy]

Ok just so you all know, the stock master works with limited clutch pedal travel.  It already has more stroke than necessary.  

[datzenmike]

Mike, you're still thinking inside the box.  

 

Most Nismo gear boxes had an overdrive 5th, but not all.  The Z-car setting records at Bonneville and all over the US has one of those special boxes from Bob Sharp.  The one I have in mind has less internal drag - by half.  Less parasitic loss + less weight + 1:1 5th gear = faster top speed.   Plus it was free, and I can get as many as I want at $300 each.  Some things are better left not talked about.   :ninja:

 

 

There were three DD FS5C71B 5th gear transmissions from Nismo with various ratios 1, 2, 3 and 4th. Not that it matters as all 5ths were straight through.

 

Straight through is 1:1 no?

 

 

Rally option....... 3.321 / 2.27 / 1.601 / 1.124 / 1:1

 

Option one....... 2.218 / 1.973 / 1.147 / 1.192 / 1:1

 

Option two........ 2.348 / 1.601 / 1.296 / 1.138 / 1:1

 

Option three..... 2.192 / 1.601 / 1.147 / 1.138 / 1:1

 

 

 All have the same top speed. 

 

Top one has the largest RPM drop shifting through the gears down through to the bottom one which has the least.

 

 

 

 

 

 

 

[Stoffregen Motorsports]

The direct drive 5 speeds are as rare as hen's teeth. I'd go for a $300 option any day of the week. Even if it were a bitch to fit.

[distributorguy]

 

 

 

Straight through is 1:1 no?

 

 

Rally option....... 3.321 / 2.27 / 1.601 / 1.124 / 1:1

 

Option one....... 2.218 / 1.973 / 1.147 / 1.192 / 1:1

 

Option two........ 2.348 / 1.601 / 1.296 / 1.138 / 1:1

 

Option three..... 2.192 / 1.601 / 1.147 / 1.138 / 1:1

 

 

 All have the same top speed. 

 

Top one has the largest RPM drop shifting through the gears down through to the bottom one which has the least.

 

 

 

 

 

 

 

Not only do I not want any of those gear selections, good like finding one of them.  Then good luck being able to buy it.  Then good luck to find one under $6k.  I know they exist.  I even know where there at least 2 sitting on the shelf.  Or I could rip apart a bunch of transmissions and assemble one, but Nismo never had drag racing in mind, so they're just not set up for what I need.  

[datzenmike]

Mike, you're still thinking inside the box.  

 

Most Nismo gear boxes had an overdrive 5th, but not all.  The Z-car setting records at Bonneville and all over the US has one of those special boxes from Bob Sharp.  The one I have in mind has less internal drag - by half.  Less parasitic loss + less weight + 1:1 5th gear = faster top speed.   Plus it was free, and I can get as many as I want at $300 each.  Some things are better left not talked about.   :ninja:

 

Well what do you want??? OD or no OD????? 1:1 will have lower top speed than an OD transmission all things equal. 1:1 will be stronger and probably less internal friction.

 

So how am I thinking inside the box? I listed 3 Nismo direct drive 1:1 5 speeds. Hell a 4 speed is DD top gear and will go the same speed.

 

If you are allowed some non Nissan transmission then yes.

[distributorguy]

The rule book simply states "Any transmission."

I want 1:1 5th gear, and 4 gears to get me to redline as fast as possible, with minimal internal drag.  The more time I spend at peak horsepower or close to it, the better chance of a record.  So I want a push start (allowed) to get up to 4000+ rpm for starters, then a close ratio 5 speed with no overdrive as that will essentially cause a lack of leverage.  4.30 rear gears, a short tire, and a redline speed in 1:1 that puts me over the old record of 129.6 at 2 different mile markers on the same slippery 3 mile course.  Its a hell of a lot more complicated than it sounds.  A Z-5 speed is the backup plan, but not any better than providing a basic function.  Yes, anyone can point out unicorns wearing hen's teeth necklaces on the internet. I ask why?  None exist.  Most Nismo boxes made were NOT 1:1 in 5th, and an overdrive would be useless when you are fighting a 130 mph wind in a 2L truck with 20 square feet of frontal area.  I'll be struggling to break 225 hp.  This is on the brink of being impossible.  

[Stoffregen Motorsports]

I guess I don't understand much about salt racing. Do you need close ratios to get up to speed?

 

You could always use the Z 4-speed.

[datzenmike]

3, 4 or 1:1 5 speeds still have the same top speeds.

 

Close ratio boxes just have less RPM drop between shifts but same top speed.

 

You could use an over drive 5 speed and just change the rear diff ratio. (A 1:1 box would put less stress on '5th though)

[Stoffregen Motorsports]

I think the parasitic loss of the overdrive is a real HP killer. Especially when speaking in terms of top speed.

[datzenmike]

A DD 5 speed may save a small amount of bearing friction as power is transmitted through the counter shaft. As far as moving transmission oil they would be the same. All things equal a 3 peed would have less losses.

 

Because of transmission design, the counter gears are immersed in gear oil and are constantly engaged to and spinning all forward gears on the upper mainshaft except 4th in an OD, which is a straight through, or 5th in a DD transmission. The counter shaft is always pumping and throwing oil all over, at all times the transmission is turning, and has nothing to do with what gear you are in.

 

An OD transmission lowers engine RPMs so you could adjust your final top speed/RPMs by changing the differential gearing to suit. OD 5 speeds are not intended for full top speed RPMs though and a poor choise because of this. Only advantage to a DD 5 speed over a OD is there is no stress on the counter shaft as it drives straight through the transmission from clutch to driveshaft. It would better support full throttle, full RPM power.

[distributorguy]

This has gotten WAY off topic.  

Problem solved.  

Solution posted.  

[Stoffregen Motorsports]

Off topic is fun.

 

I got my 18# of Nueske's bacon I ordered last week.