Bleeding the breaks
 

We inherited a 1977 Vette that's had a lot of work done but do to circumstances I only know what I can see. That said the break pads have been replaced but the calipers a full of air. I've done countess break jobs through the years but this is the first time dealing with multi piston calipers. I'm using a break fluid pump and have pumped nearly a half gallon of fluid through them but so far can only get one of them clean. Is there a trick to this?

Are you bleeding in the following order: RR, LR, RF. and LF? You are pressure bleeding? IIRC, there are two bleeder screws on each caliber.

Yes. I'm working RR, LR, RF, LF. I using a pneumatic pump. Yes, there two valves, but only on the rear and I'm bleeding them inside to out. From what I've researched it looks like its correct.

What's the indication that's telling you that the calipers are still full of air?

ive never had a problem with gravity bleed. When releasing the brake pedal , do it SLOWLY,. also check to see the master cylinder level does not go too low.
remove bleed valves and blow compressed air thru them.: a hand pump will work well.

Only rear calipers have 2 bleeder screws--not sure why