The Stovebolt Site Forums The Shop Area Driveline Dual Master Cylinder/line size questions

I order the following dual master cylinder....

Dual Master Cylinder

I was reading through cletus's tech tip but still have a few questions.

1) The ports are different sizes. The middle one is 9/16 and the rear is 1/2. Why is that?

2) Does it matter which one runs to front/back? The chambers appear to be the same size.

3) Can I run fittings to reduce the port sizes down to standard 1/4" line size? (I am considering buying precut lines that are already flared)


4) My front lines currently appear to be 3/16's. Cletus indicating running 1/4 to the front and to the rear flex hose. Why 3/16 just in the rear?

5) If I get creative with how I run my lines, does it matter if my lengths are different that what cletus indicated?

I know these are some pretty simple questions to most of you and I hope you don't mind my inexperience.

Thanks in advance.

Ron

Hy The Hill Boys, which master cylinder port is used for which system is dependent on whether you are running a disc/drum, drum/drum, or disc/disc system. If you are running a disc/drum system you will need to run the master cylinder outputs through a combination valve, this is to insure that the correct pressures and flows go to the correct systems. In general most master cylinders are plumbed with the primary (closest to the pushrod) operating the front system, but I have seen vehicles plumbed the opposite way. As to the different size ports this was done to make the installation of a replacement master cylinder "idiot proof", so the installer could not plumb the systems opposite to the design. You can purchase adapters to bring the ports to a standard line size, or you could use the nuts which fit the master cylinder ports and are appropriate to the line size you intend to use, hope that helps.

Thank you. I'm doing drum/drum. I was not aware that you could find different size nuts for the same sized line. The local NAPA seemed to have different size line and each had a bigger sized nut as the size of the line increased. That is why I thought I would need an adapter.

It appeared to me that cletus's tech tip had the rear port going to the front and the front to the rear. That why I was asking.

I've always used 1/4' on drum and 3/16 on disc.
Line size is doesn't make a difference when applying or to create line pressure. Using larger size for wheel cylinder is because you need the fluid to leave the cylinder faster than on a disc which doesn't retrace as far. Wheel cylinders eject more fluid when the springs retrace the pistons so larger lines, 1/4", make that easier and less likely to hang momentarily. Disc piston doesn't retract that much and the disc run out will force the fluid out as far as needed. If you look on a old C50 C60 it will have 5/16 line and huge cylinder. if you have 3/16 on their now go with that it may have small cylinders and larger in the back