67 Camaro brake question

I just tried to power bleed the brakes (front discs) on my son's 67 Camaro. I started with the closest to the master cylinder , in this case the left front and then the right front. After I finished I put the front tires back
on and found out both front brakes are locked. This is first time I used the Mytivac for this purpose and ran into this problem. I don't have a Camaro manual but I do have a 73 Nova manual. In that manual it states one must hold down the metering, proportioning and failure warning switch. Unfortunately the car is 15 miles away and I can't look at the system. Is there a similar valve in the Camaro system?
Thanks
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Michael,
Are these factory disc brakes? The factory four piston calipers were notorious for leaking and sucking air.
Yes, you should have a proportioning valve and a metering valve. On newer vehicles these two would be combined to make a combination valve.
The proportioning valve makes sure more pressure is directed to the front disc brakes as disc brakes require more pressure than drums.
The metering valve delays the pressure to the front brakes so the drum brakes can "catch up". Most power bleeders use about 15-20lbs of pressure in the bladder. This is not enough pressure to open the metering valve and fluid would not flow to the caliper.
Holding the metering valve open should only be needed if you are using a power bleeder. Bleeding brakes normally with foot pressure on the brake pedal should not require holding the valve open.
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