Hot Rods No Brakes

58 GMC 1/2t truck; front disc drum rear, Wilwood residual valves,mc mounted under the cab
Can't get a firm pedal with the master cylinder.Bench bled& installed several times. I want to try a different mc.How to tell what I have OR recommend a master cylinder.
Thanks

 

When you say bench bled, which doesn't necessarily have to be performed on the bench but that's another matter, did you have the master orientated such that no air could be trapped in the cylinder? Typically this means having the input to the cylinder slightly elevated ( air can escape into the resevoir). This can possibly be achieved on the vehicle by raising or lowering either end to suit. I've had to remove rear wheels and set the rear down almost on the brake drums as well as raising the front slightly. Seems like a lot of effort but was much easier than removing the master. Taught me a lesson to keep a stricter eye on the fluid level when bleeding!!

Chris

 

Ran into the same thing recently. Pulled the master out to re-bench bleed. During this I noticed one of the circuits was not flowing like the other. Replicated the bench bleed on another m/c and both circuits flowed the same. Put that m/c back in the 39 and got pedal again. As far as I can tell the original m/c was byp***ing one circuit. Damn thing was only a year old...
Try watching the flow during bench bleed and see if the m/c is junk.

 

I just finished up my disc/drum brakes on my 41 PU. used this MC after of course knowing the Pedal radio, caliper area calculations. MC is mounted on firewall. Brakes are as good as on my new F150.

 

I had the same issue on my A roadster, turned out that one of the Wilwood residual pressure valves was bad. And I think some others have had problems with those valves...