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Mr HEMIFRED, have you found your problem yet? Mine is doing the same thing as yours. We even pressure bleed them,no air in system no pedal. When we get all the air out it feels like it has a pedal,but when you push it down to the floor it goes. New master cylinder,new hard line to the rear,new calipers(all Wilwood). I just replaced the 2 braided steel brake lines to the calipers,will bleed the system again this afternoon. I have been told the braided lines never go bad,but that is the only things I had not replaced yet. I have never run a residual valve on my dragster before,Wilwood says to have brakes I must have one. My understanding of a residual is if you do not have one the fluid can run back to the master cylinder and let the piston retract back into the calipers and you will have to pump the pedal a time or 2 to get the pedal back up. That's not my problem you can pump the pedal all day and they never hold. They are like yours block off any line and they hold.

Hope you have fixed your problem and can tell me the fix.

P.S. I am sure you check this also,with one of the lines unhooked to the caliper when you push the pedal to the floor how much brake fluid come out? Mine looks like about a teaspoon full comes out.

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Mine has had the wil-260-6765 7/8" bore master cylinder(these are called high-volume) & the wil-120-6818 .380 thick rotors & 1.75 pistons since the dragster was new and worked fine. When the brakes quit I replaced 1st master cylinder then calipers (both with the same exact parts). I replaced the 3/16th hard line back(that runs through the bottom tube on dragster) to the T that runs a 3/16th hard line(which I checked for for damage) to the other side of the dragster. The steel braided brake lines going to the calipers were the only parts left I could not verify(they did not leak or swell,hoping maybe they were swelled a little on the inside).So I have just replaced them & will bleed the brakes again tonight. The tech. at wilwood said they had never seen a braided brake line fail,that was not my problem. They said before I could have brakes I would have to have a 2lb residual valve. Which I have never had,after it sets for a couple of weeks I have to sometimes pump the pedal once or twice to get it back up but then it stays up. I understand that but my pedal will pump up & feel hard but will still go to the floor. When you have your foot on the pedal that should put more than 2 lbs of pressure and keep the fluid for running back. Unless my master cylinder got weak & I got another new wilwood master cylinder that was weak I am lost.

Anyone have any suggestion feel free to chime in. Wilwood said the steel braided lines I just replaced were not the problem. If after bleeding the brakes this afternoon if that is not the problem,I am back at square one.

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I would put the residual valve in... reason is that
the old caliper most likely didnt have the roll back
boots to pull the piston back all the way and the
new ones do... the residual valve would correct that