Well, since I didn't get any responses to my prior question...

I've got a project '72 EC that's always had a hard pedal pressure problem. The car has been through several owners. The last owner said he put a "new" manual master cylinder on. I've tried about everything to no avail.

Is there any way to tell if this thing originally had power brakes?

I have to ask: what does it matter if it "had" power brakes?

I would think what really matters is what it has now and if the parts are all compatible and all working nominally. I would also think, although I could be wrong, that by '72 they all had power front disk brakes?

A hard pedal could suggest that A) the vacuum brake booster is not working or B) the master cylinder is the wrong model. I might carefully try disconnecting the booster line to note if there is a difference (be sure to plug the line while it is disconnected). Do not do this in traffic or at high speed though of course...

If there is no change in pedal feel then you have isolated the problem to the brake booster. I have heard that, since it is cheap, replacement of the check valve is a good start. I would also verify you really have vacuum at the booster. If this all checks out and still no joy then it may be time for a new booster.

I believe decoding the cowl tag will tell you if the car had power brakes or not. 72 was still pretty early for power disc brakes to be standard, my 71 (same gen) was 4 wheel manual drums.
Are the brakes truely hard, or do they just seem that way as you're used to driving cars with power disc for so long. I know that's how I felt when I first bought my 71, then I realized that yes this is how brakes were when I was younger. 4 wheel manual drum is substantially harder than power drum or power disc.
I guess the first question to ask is: are the brakes truly hard, or is this just your perception?
Look on the frame below the master cylinder where the lines from the master cylinder run to. If they go to a simple distribution block it is set up (probably from the factory) for 4 wheel drum, if they go to a proportioning valve then it was power disc.

Thanks MaMa,

The pedal is just hard. I've got a '67 Chevy with manual brakes and this EC is just hard and low.

In a prior question I tried to find out if there was something on the cowl tag to denote power brakes, but I didn't get any response RPO-wise.

To be honest, I haven't checked the proportioning valve to see what type it is.

My nagging feeling is that the previous owner may have put a manual master on an original power brake car. I guess it boils down to whether or not the brake system after the master is the same, power or not.

Doing a little research in my assembly manual this morning, this might help you. This is on a 71 but should apply to your 72. Power brakes appear to be RPO J50. The rod on a manual master cylinder attaches to the brake pedal at the upper hole, power disc at the lower hole. Manual brake distribution block is attached to a bracket then the bracket is attached to the frame, power disc proportioning valve is bolted directly to the frame. Manual brake pipes come off the master cylinder coil around then drop directly to the distribution block, power disc pipes come off the master cylinder wrap around the back of the booster (no coils) then go down to the proportioning valve.
Free play at pedal is .06 to .25 on both.
Note from assembly manual: Brake pedal must support a 50lb. load at "B" (brake applied) after traveling a maximum of 3.00 inches (1.75 inches disc brakes) after brakes are applied three times in quick succession & free play is .06 to .25 inches. If 3.00 inches or 1.75 inches is exceeded, brakes should be rechecked for proper bleed.
Both systems are the same after the distribution or proportioning valve.
I would seriously doubt if someone would go through the trouble to convert from power to manual brakes as it would require changing more then just the master cylinder.
My bet on your problem is this: you stated that the previous owner had put on a new master cylinder which leads me to believe that it was not bench bled correctly if indeed the pedal is low. If your pedal travel exceeds 3.00 inches as stated in the assembly manual note, remove the master cylinder and properly bench bleed it then immediately reinstall it followed by properly bleeding the entire system.

A freind of mine told me that if you jack the front of your car up a bit, and then brake the bleed screws loose and let the brake system gravity feed/bleed, that this will take all of the air out of the system, Its a slow process and can be a mess, but supposedly a more efficient way of bleeding ALL of the air out. Has anyone ever done this? In theory, sounds like it would work.

I don't think this would work as it relies on gravity and not pressure to force any air out. Air has a natural tendency to rise to a high point and stay there unless forced out by pressure. In that method the air would either block the fluid or allow it to seep past the bubble.

Thanks for all the input guys. There's a lot of things I can check. I have wondered about the master cylinder

I think the previous owner started with a basic shell and "band-aided" it back together. You wouldn't believe some of the stuff I've found. It's got an early '67 rear end and an entire dash that's not for this model. I started to work on it but got sidetracked when I bought my '86 EC.

Wish me luck.