vacuum question

I built my '70 340 motor 040. over, 915 2.02. heads with three angle valve work, KB 10.2 hypereutectic pistons, Comp Cams XE268 cam, super comp roller rockers, Edelbrock performer RPM intake and Edelbrock 800cfm performer series carburator. The car pulls very hard and I am happy with it's performance.
Why do my power brakes feel like I'm pushing on a brick until the motor is warmed up?
Author: admin