Brakes low on vacuum
I have a big cam 240/244 .605/.598 112+4 and I can push the brakes only twice before I run out of vacuum. Car is making 10inhg at idle, 18inhg at 2000rpm (my cruising rpm), and more than 25inhg after 2500rpm. I do have a vacuum reservoir and both my booster and reservoir's check valves work. I don't think the booster leaks because I can hear the vacuum escaping when I remove the check valve.
When driving on twisty roads where I keep the rpms high the brakes are ok. It recharges the vacuum fast enough before the next turn. On highway though driving between 1800 and 2000rpm I have no vacuum. Even after driving for lets say 10min , when I push the brakes there is no assistance.Its like I am loosing the vacuum on the highway (I know it sounds crazy). I already checked for vacuum leaks and there is none.
What can cause this?
How many times should I be able to push the brakes before I run out of vacuum. I would assume 4 or 5 times with the reservoir, but I can do only 2.
Can I install manual brakes with SS lines? I am using the stock brake calipers so only 6 pistons to move. My first car had manual brakes and it was perfectly fine but was only 2300lbs and had single piston front disc and drums on the rear.