This is a bit of a continuation from my last thread ( http://www.c3vr.com/vrforums/master-cylinder-question_message421197.html ) but this question is more specific to brake bleeding so I started a new thread.  Anyway, I can't seem to get the fronts bled properly - they just spit a little fluid, no solid flow at all, no matter how many times I do the pump and bleed.  (I asked my wife to do some pedal pushing tonight)   I've also supplied the bleeder with a generous vacuum source and same thing - it will pull some fluid through but not much.  It almost seems like there is a blockage somewhere.  Could this have anything to do with the proportioning valve?  I didn't touch it, but did disconnect, remove, and re-install the line that goes from the valve to the right front wheel.  

Sometimes the threads around the bleeders will allow air back into the system. I had to put some thread sealer on mine and the bubbles stopped - solid stream of fluid. Also make sure not to open them too far. 1/4 turn should do it. 

Disconnect the line from the M/C to the pro valve if the break fluid flows pretty good it's probably the valve, which I would & do replace on theses old C-3's. 

Dave, remember the service manual mentioned about forcing open the proportioning valve. knotacare might have a point about the valve being bad or even plugged/restricted. 

Thanks, guys.  I'll focus my attention on the pro valve next.  Any suggested vendors for a replacement?  I've even had a hard time finding one on some of the online catalogs - I guess some call it a "distribution block" others "proportioning valve" and still others "proportion valve".  Would love to know where others have purchased theirs.  

Dave here is a link to what I used.....................

http://www.ecklerscorvette.com/corvette-brake-proportioning-valve-1974-1977.html

This is where I get mine

I bought the brass one, but I like your price better.

Dave, I just got done bleeding my brake and my blood.......actually my sweat. I would rather pull the engine/transmission and body than do the brakes again. I did them myself.....tough to do. I had previuosly bench bled my new master cylinder in the vise. I have completely new stainless steel brake lines and new brass diverting blocks. Also all new stainless steel flex hoses. I had flow to the front brakes. There are actually two bleeders on all 4 calipers. The rear brakes I couldn't get any flow. I even opened the connection off of the proportioning valve. I then connected up a pressure power bleeder to the MC. I pumped up the pressure to 15 psig. I left the bleeders completely out of the rear calipers. I finially got flow to the rear by pumping the pedal. I'm using dot 5 silicone fluid (purple). I put the Russell check valve bleeders back in and opened individually each one less than a quarter turn. I pumped slowly in on the brake petal and held it down for at least 10 seconds. I did this for all 4 bleeders in the rear about twelve time apiece. I then went back to the fronts and repeated the same procedure. I almost filled a Mason jar with the purged brake fluid. When I came into the house my wife had to dry off my sweat when she saw me (she's a keeper). Well anyhow that's about the worst job of my project so far. I sure hope everything works out for you. Oh and by the way the pedal is as hard as a rock