Interesting brake problem, what is a good pedal?

[andymarkv]

Hey guys!!
The 71 C20 I'm working on has had a very hard brake pedal since the first time I've driven it. Is this normal?

I replaced the calipers and front brake hoses, the pedal was till hard and didn't stop well. (even though the calipers were close to stuck)
I replaced the booster and master cylinder (19" of vac to the booster) and checked for binding in the brake pedal movement, still hard pedal doesn't stop well.
Changed the proportioning valve with a stock style one, I believe it is bled correctly, there isn't a brake light on, tested for continuity at the switch post (its open), the rear brakes don't lock and the pedal is sill hard and doesn't stop well.

My father in-law says that it takes a little more effort than he is used to to push the pedal to bleed the front brakes, but if he pushes with medium effort I get great fluid return out the bleeder.
What the heck is going on?!?!?!?!?
I've never heard of blockage in the steel line or Y block that separates the left and right front brakes?

Or do 67-72 Chevy truck brakes just stink, like the 99-04 Silverado's have a mushy soft pedal even when working correctly?

[LockDoc]

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Was the replacement booster new or used? For some reason it sounds to me like a booster or vacuum problem.

Does the engine have a cam in it? (other than stock)

LockDoc

[andymarkv]

New booster from advance auto.
I did put a very small cam in it. But it was like this before with the stock cam.

Anyone ever heard of the steel line getting rusty/plugged?
It has the original hard lines still on it.

I just can't think of what else it could be?

[Alex Hayley]

Do you have a way of testing the new booster to ensure it is holding vacuum? Also, do you have a vacuum reservoir/canister?

[andymarkv]

I don't have a good way of testing if the booster is holding vacuum. It does idle very poorly with the vac line open and calms right down with it connected. The truck is almost impossible to stop with the booster vac line disconnected.

No vac canister. There is 19" of vac at idle, plenty to run the booster.

[68gmsee]

Have you done anything on the rear brakes? The rubber hose on top of the axle can also be internally swollen so be sure and replace that one also.

The rear brakes don't do the majority of the braking but they do assist the front ones. A brake shop guy once told me it was about 60% front and 40% rear braking action. Make sure they're adjusted correctly and working correctly.

Lastly, make sure you have bought the best brake shoes and pads you can afford. There are some that just don't have good stopping friction power.

[andymarkv]

Yep, decent semi metallic front pads.

But you're right, I haven really done any thing in the rear. I did crack the bleeders and got good fluid return when the pedal is pushed.

I'm going to pull the rear all apart tonight and see if there are problems.