85 IROC 4w disc - all OEM stuff

Car has new calipers, new rotors, new carbon, metallic pads, new rubber lines, a new master, the prop valve was rebuilt and I still feel like the pedal is spongy -

i get a slow stream out of the rear calipers when bleeding but it doesnt shoot out!

more pressure in the front for sure when bleeding but Im still not happy.

for reference, i have 6 other old cars - from the 60s and they all have a firm pedal and you can easily lock em up if you tried where as with this one, You absolutely cannot lock this car up on dry pavement

I did the Granger spring swap in the prop valve as well

what else could it be?
Or are these cars just that bad braking wise?

 

I have an 88’ GTA with Delco moraine 4 wheel discs as well and what I did to improve braking performance was add a Wilwood adjustable proportioning valve and braided stainless brake hoses by Goodridge (improved pedal feel).

I noticed the most improvement with those mods, I also run Stillen pads in the front. I pretty much followed a thread about ultimate stock brake set up by a few other members.

I tried the prop valve spring mod too and not long after developed a leak from there…

The brake hoses I replaced looked rough, especially the rears which were date coded originals and I replaced the hard lines on the axle as they were looking rusty.

 

Those rear iron calipers.... suck to put it mildly.