Need expert advice with my 5 Lug Convo.

Brake Expert Advice please.

I did a 5 lug convo on my 86 using SN95 parts. I used a 85 Lincoln Towcar MC and gutted the Pro. Por Valve like Matt's website says. I also installed a knob style Adj. Pro. Por. valve. The problem is, I have a mushy brake pedal. I blead the lines and they are free of air. When I step onto the brakes it feels mushy then they kick in when I push about halfway, then they stop like no ones biz. If I immediately push the pedal again, it seems like I have normal brakes. So I have to pump the pedal to get a nice firm pedal when I am driving. So I would like to know how I can get the pedal to be normal all of the time. I twisted the knob a few times and that seemed to help, but did not rememdy the situation. I thought about maybe adjusting the brake booster out a bit if that might be the problem. Thanks!

ttt

I am using the rear disc brakes form a 94-04 stang. Yes, you guys were right, I blead them tonight for the third time, an assload of air came out of the front passenger side. And all I can say is holy crap. Nice firm pedal and man do they stop. I was going to buy the 13 inch cobra fronts, but now with 99 dual pot pbr's, this should be better than 10 inch rotors and drums.

Kinda scarry though. I was on the freeway, and I stepped on the brakes and they went to the floor and nothing happened unless I pumped it 4-5 times. Thank goodness this is fixed. I was starting to get pissed and started to regret my decision of dumping in a boatload of dough for the brakes and wheels and tires.