Just put a 1987 911 carrera front end on my car, rebuilt the brakes, new rubber lines, and some new hard lines as well. I set the venting clearance on the rear calipers, bled the system, and the brake pedal is still spongy...any ideas?

tap the MC with a hammer. There is some air in there somewhere!

Agreed, rebleed it twice. Drive it and let it sit for 2 days, then rebleed it again 2 times.

It is amazing how difficult it can be to get all that air out.

Good luck!

bleed the prop valve too

these cars are kinda hard to get bled perfect in one shot...