power 4 wl disc lacks power.

[68gmcJames]

New here , but hopefully folks can take pity on me and checkout my set up and see if they know how I should proceed. I've written the big brake manufacturers. Baer wrote back so far and is trying to help me out (which is awesome considering I'm using factory parts) but thought with a bigger group someone might know just what I need.

Truck is a 68 gmc



Brothers truck parts 8" dual booster with 1.125 bore old vette style master

Front is 11.85 x 1.25 rotor. D52 oem calipers

Rear is a cobra irs with stock brakes. 11.65 disc , 40mm caliper (internet said so)

I don't have a way to measure pedal pressure. Thought about analog bath scale...but I gotta find one. Max psi on master ports is 1400 , engine idling with 13-14 in of vac. ( I've read more vacuum would be better, but that's at idle vacuum , not built up from driving. Also I have a vacuum can.) Haven't checked at calipers yet.
That psi is pushing on pedal extremely hard. Same force without running on empty booster gives me 700psi. Brake lever was redrilled per instructions with brothers kit.

I have a jegs adjustable prop valve that completely open limited psi to 500. So I pulled the oring and reinstalled it to test. Rear pressure then matched front and improved stopping.

Front brakes have about 500 miles on them but about 15 years old and I don't even remember what kind of pads they are. No rust, stored inside. Rears all new stuff. Just stock replacement parts.

The truck stops decent . Probably better than it ever had really. But it doesn't have the power to lock up the brakes so I feel I'm missing out on some stopping power.

Tires are nitto 420s. 255/40/20 on 9" wheel and 285/40/20 on 10" wheel.

Lowered in front 4" with belltech spindles and springs. 1 3/8 swaybar. Adjustable rancho shocks.

Irs has qa1 single adjustable coilovers with 350lb springs. Stock cobra swaybar.

I have read through the stickied brake combo thread here and learned a good deal. It seems strange that the d52 calipers are supposed to create so much brake torque but I have this issue , unless the difference is in the pads.

I ordered some hawks hp plus pads for front and rear to try, but waiting on those and wanted to run this by everyone to get some thoughts.

Big bias to the front too it seems, but its a very front heavy truck I imagine.

Thanks for any help
James