Brake pedal is really stiff

Thanks for the replies guys. Yeah I made a mistake calling it a prop valve but you know what I mean. I did measure the bore size when I put the MC in a few months ago and it was 1". It bleeds fine. Only problem is once the system gets most of the air out, the pedal becomes hard as a rock.

I'm obviously no expert but I've managed to keep my Duster's 9" brake system running fine for 10 years now as my daily driver. The only real difference in that system and the Valiant's system is a 1/16" difference on the MC bore size. I wonder if that could just be the only problem?

I'll research that 7/8" MC, thanks!