G50 box: size of master+ slave cylinders?

[911hillclimber]

By chance, does anyone on here please have the diameters of the master/slave cylinders of a G 50 gearox used on the original Porsche?

I think the sizes in mm are cast into the bodies.

Thanks, Graham.

[robm3]

911hillclimber said:

By chance, does anyone on here please have the diameters of the master/slave cylinders of a G 50 gearox used on the original Porsche?

I think the sizes in mm are cast into the bodies.

Thanks, Graham.

Try the Factory, they supplied me a new slave cylinder.

[911hillclimber]

Thanks Rob, will do.
Graham.

[ricola]

Graham,
I measured the 911 master at 20mm diameter, haven't had the slave off to measure as I plan on using it still. I've got a 3/4" master to use (19.05mm) and a slightly longer stroke which I'm hoping will do the job.
Rich

[911hillclimber]

Thanks for that.

My problem is none Ultima, but you lot are very helpful, so I have asked on here!

I have a Lola mid engined race car with a 911 3.2L flat 6 in there with the dreaded 915 gearbox which is cable operated.
I have converted the box to hydraulic by simply putting an AP Racing 0.75'' slave and a Girling 0/75 master to do the work. The clutch is a simple Sach sports clutch as the engine is only 240 bhp and the car weighs 600Kg with me in it.

The pedal weight is huge, and although only a hillclimb car it is hard to control quickly. This is down to pedal/leverage ratio as much as anythin but i need a full 20/25mm stroke on the slave to clear the clutch.

I wondered if the G50 system used something different to the current set-up.

[Steve_D]

I have a couple of AP master cylinders which I will be ebaying in the next few days.
One is 19.1mm (3/4") with a 25.4mm (1") stroke.
Other is 20.6mm (13/16") same stroke.
If either of those are any help let me know.

The standard Ultima clutch setup is very heavy but some have gotten away with changing the master cylinder and still had enough throw on the clutch. However I can't remember the slave and master sizes.

Steve

[911hillclimber]

Thanks Steve.

The issue is indeed getting the stroke for the 911 clutch with a reasonable pedal weight. Porsche would not sell the cars if the pedal was too much, so there must be a combination in the stock system that works.

If you decrease the master smaller than the slave the pedal effort reduces but so does the stroke.