When i converted to 4 wheel disk from 4 wheel drum i consulted the local brake shop about my inteneded setup, master cylinder, etc... they basically said "if it works it doesn't matter." I actually drove my car down there afterwards and got them to check it all out and nothing like this was mentioned.

Both front and rear lines had/still have those rubber valves in my car. Does this mean that i would havel fairly substantial brake drag that i haven't noticed? ugh.

Habib's Brake and clutch?

There are 2 types of valves
Disc and drum
Drum ones look like the pic
Disc ones look almost the same but have 2 thin grooves down their lenght. This allows them to pass pressure on pedal release. They hold between 2 and 4 lb pressure which is ok for discs.

I know that this is an old thread, but i think that this is relevant.

When i was an apprentice, that rubber valve was called a "residual pressure check valve" & its purpose was to maintain a small amount of hydraulic pressure in the line at ALL times. This was to ensure that the lip of the rubber cups remained in contact with the bore of the wheel cylinder to prevent any possibiliy of air entering into the cylinder.
The pressure was nowhere near high enough to offer any real opposition to the function of the brake shoe return springs & so had no effect on brake release performance.
Thats the way it was taught to me & i have never had cause to doubt the truth of this.

Disk brake calipers have no real method of returning the piston into its bore, save the small amount of springiness in the piston seal. This will draw the piston back into the bore by a very small amount, which is exactly what we want. If the residual pressure check valve is not removed when switching to discs, this small amount of residual pressure in the line will prevent the piston in the caliper from drawing back enough to allow the pad to clear the spinning rotor, creating the drag that you are experiencing.

If you are messing with something as important as brakes, it's probably a good idea to learn all of this stuff BEFORE doing anything that can seriously endanger other road users.

The Datsun 1200 master cylinder for disc-brake models also use a check-valve. Perhaps it is for lower pressure than what the drum-brake requires.

So remove this if you know your cylinder is for drum brakes (7/8 bore), and you are fitting disc brakes. Otherwise leave it in.

Thankyou,.... and very much taking in

will this give greater pressure to the back cylinders if so this is my answer i drave my car around the yard the other day and i had a had problem with braking where the fronts took all the breaking i have 11/16 rear wheel cylinders and sunny front struts

If you have a booster, then your reaction disc is missing. If you've had the master cylinder apart, are you sure that the seals were put in the right way. Otherwise it could be a biasing problem with the splitter valve, that apparently also does biasing. I tried to use an old corolla one once, and the bias was screwed. I used the LB Lancer one, and it was all good. I wanted to use the corolla one, because it had a warning switch installed to tell you that one of the brake circuits has failed.

Chris