Hey folks I have an 82 camaro with a small block I've swapped into it. I replaced the rear drum wheel cylinders, rubber hose and hard line. Replaced the rubber hoses up front also. Brakes have been bled with both a vacuum hand pump and the old school way with a helper. 0 air, all fluid. No visible leaks or loss of fluid in the master cylinder.

When I push the brakes (car off) they feel good, and the pedal pops back up.

When the car is running and I push the brakes or push the gas it slowly sucks the pedal to the floor I have to pull it back up with my foot to get them to unlock.

Today I unhooked the brake booster, and I have good firm brakes (kinda junky with no booster power). Plugged it back in and the same issue where the pedal would stick to the floor.

I believe my booster is bad, or my master cylinder is toast (but doesnt explain why it works without the booster).

Any ideas? Anyone experience issues like these?
Any tips, hints or ways to test the booster or the master cylinder would be awesome

 

Try the diaphragm in the booster. It’s very common with those brake boosters or just the booster in general as a whole assembly, but more often than not the diaphragm alone go bad and have leaks internally and from age and/or degenerate not holding the correct vacuum which in turn can/will cause the brake pedal issues.