Brake problems ( HELP )

I built a 1930 street rod with a 4 inch drop axle in front with 9 1/4 rotors and a chevy s-10 drum rearend . I installed a pedal ***embly under the floor . It was a complete kit with booster , master cylinder and pedal . The front end came from speedway (new ) and the rear end brakes were completly rebuilt . I installes pressure valves because the master cylinder was lower than the calipers . I never could get the brakes to stop the pedal would go down and get rock hard but would not stop the car . I changed the master cylinder and got the same thing . Then i ordered two willwood master cylinders 7/8 fore the front and 1 inch for the rear and mounted them on the firewall , brakes are a little better but still will not lock up the brakes . car weight is about 3500 lbs . the pedal ratio is 7 to 1 .anyone get any suggestions.

 

when you say "pressure valves" i ***ume you mean residual pressure valves...right?

do you also have an proportioning valve?

 

no it is set up on the pedals , just like on the willwood pedal

 

no proportioning valve

 

brian , i have no idea what that means...so i will ask: do you have a proportioning valve?

if you built the car and don't know what one is i can ***ume you do not have one?

 

I ***ume the front has the Mustang II caliper and rotor then?

Bleeders pointed up?

No loops in the lines and no lines above the masters?

 

Master cyclinder and pedal ***mbly like this?

 

Sounds like a booster problem to me. Since it's an engineered kit - I would start there. Is the push rod gap adjusted correctly? Enough engine vacuum?

 

the pedal is setup with a himejoint that alows pressure to even out between the two master cylinders . that is considered the proportioning valve

 

yes that is correct but i made the pedal longer , witch should help the ratio but?????

 

I'm wondering if the shoes on your drums are adjusted improperly or if they are hung up on the backing plates. Could be down to the shoes installed incorrectly also, shorter or lighter colored friction shoe in the front.

 

Ah, when you made the pedal longer did you allow for the extra travel? The cylinders should be able to compress 1-1/4" to 1-1/2" from rest to fully depressed.

 

no booster just 2 master cylinders .I put a guage on the front brake lines and the most pressure that i get is 550 lbs . What should it be

 

the pedal comes all the way up and it does depress aboyt 3 inches untill it is rock hard

 

800 ish is normal operating pressure but at maximum force it can be over 2000 psi

 

Are your rubber lines good?

 

what about the front calipers , could something be wrong with them , they open and close finr when i take them off , hold in my hand and someone pumps the brakes.

 

You have residual valves in the system? Are they pointed in the direction of flow TO the wheels?

 

i have all braded lines from speedway

 

took the valves out when i mounted the mastercylinders on the firewall

 

how do i achive 800 lbs

 

Also on your master cylinders, the piston needs to retract all the way. Remove the cover and use a flash light to peer down into the resevoir and look at the two small holes. Have someone depress the pedal slowly and watch the fluid transfer holes to watch the piston move. When your ***istant releases the pedal (slowly so you don't get squirted in the face) you should see the piston clear both holes in the bottom of the resevoir. If not you need to adjust your balance bar and heims to let them do so.

Also your balance bar should be in the neutral position before starting any adjustments.

 

check for flex in your caliper brackets, shoes and drums.

 

the master cylinder should put out 800 lbs directly ?

 

If everything is in good working order it may be necessary to reduce the size of your master cylinder bore to acheive higher line pressure with the same ammount of pedal force.

 

Are you using the right size brake line for the calipers and master?

 

does the tubin size mater

 

at a minimum, yes.

If you remove the line from the master cylinder and put your gauge directly to it you should be able to generate much more than 1500 PSI

 

Tubing size does not matter when concerning pressure.

Fluid volume transfer is annother thing. 3/16" or 1/4" brake line is standard and either will be just fine.

 

i ***ume you are using 3/16 hard line and 3AN flexline? that will be fine , and no it really doesn't make any difference