i recently purchased a 70 ss with a 454 and front disk brakes and the pedal is rock hard and you have to push really hard to get it to stop and the rear tires lock up and the fronts don't seem to be grabbing much. i checked to make sure it had good vacuum to the booster, it checked out ok so i replaced the booster and master cylinder, still have the same problem. I did some research online and found out that in 70 they used 3 piece valve system, a hold off valve at the master (missing) a junction valve and a hold off valve in the rear. I guess my question is does the valve at the master aka golfball valve hook into the rear line or the front and is that missing valve causing my problem? i hope someone can help me , thanks, Dennis

Welcome to ECC Den. I'm not sure if this is the valve in question.
http://img154.imageshack.us/img154/1533/011an9.jpg (http://imageshack.us)
If the brake hoses are old they may be restricting pressure to the calipers.

Jim

Yes that is the valve I am talking about, thank you for the pic, for some reason i was thinking it went on the rear line. what does that valve do? Good point about the rubber lines, they are old and have cracks starting on them, I am going to replace those and see if that helps, thank you so much for your reply, I really want to drive this thing, If anyone else has anything to add, please do.

Your welcome. I'm not sure of it's purpose though. Perhaps someone will chime in that knows.

The valve at the master cylinder is a metering valve. It goes to the front brakes, it job is to "hold off" the front brake pressure till the rear brake shoes have a chance to expand to the drums.
A valve to the rears is a proportioning valve. This valve maintains a lower rear brake pressure to prevent rear lock up. There is likely a third valve with a wire. This is a pressure differential valve that indicates a lack of pressure on the front or rear side. When triggered the brake light on the dash will come on.
Your symptoms of low or no front brake pressure and hard pedal would point to the metering valve. I like to replace all these valve with the more modern combination valves that cover all three. But this takes a major change of brake lines. I do think the metering valves are now available in reproductions. Stay away from used ones or rebuilds.
Mike

Problem solved, I replaced the brake hoses and both calipers and everything seems to be fine now.

Thanks guys for your help