Odd pedal feel?

[Malicious]

Hi all,

Bleeding my brakes after rebuilding the calipers etc. having some trouble getting the last of the air out of the lines in the front. But I have noticed an odd pedal feel when pumping the brakes on the front.

I get the pedal to the floor, hold it for a few seconds then the pedal drops another maybe quarter to half inch. With a bit of a light noise.

Anyone come across this before?

74, disc front drum rear, vac power booster.

Thanks in advance.