65 GT350 Proportioning Valve

[mygt350]

On the outside of a 65 K/H Proportioning Valve, there is a machined groove which has a rubber grommet in it. What function does the rubber have?
Martin

[J_Speegle]

Covers a hole in the machined surface that works as a bleeder/vent from the spring chamber on the bottom of the housing. The rubber band/gasket works as sort of a cheap one way valve design

[mygt350]

Jeff
If the rubber band/gasket is really old and clearly cracked, assuming brake fluid would come out?
Thanks!

[6s1640]

Hi Martin, looking at the drawing Jeff posted,  no on brake fluid leaking out. The brake fluid will only leak if other seals have failed.

Take care

Cory

[mygt350]

Will send it up to Jim C to waive his magic wand over.

Thanks

[mygt350]

Am I correct that the proportioning valve only affects pressure to the rear drum brakes and has no effect on front calipers?

[J_Speegle]

Am I correct that the proportioning valve only affects pressure to the rear drum brakes and has no effect on front calipers?

Correct just like other years

[acman63]

Ive pulled apart many 65/66 GT350s that the rear metallic shoes had virtually no wear  so most bias on the from t brakes

[s2ms]

Ive pulled apart many 65/66 GT350s that the rear metallic shoes had virtually no wear  so most bias on the from t brakes

Maybe that explains why 6S1757 still has the original drums, even with all the racing in the 70's. Had them turned when I did the brakes in the early 90's and there was still plenty left to turn again.

[Helmantel]

Ive pulled apart many 65/66 GT350s that the rear metallic shoes had virtually no wear  so most bias on the from t brakes

And yet they needed cooling in 1966

[Bob Gaines]

Ive pulled apart many 65/66 GT350s that the rear metallic shoes had virtually no wear  so most bias on the from t brakes

And yet they needed cooling in 1966

Not really . If you think that the 66 scoops cooled anything I think you need to take a closer look . The air blows on the tires not the brakes . It was cosmetic

[Helmantel]

I know. I had to laugh the first time I looked at a 66 Shelby and noticed the "tire coolers"

[gt350hr]

  The valves were set to work with "hot" brakes. If you set the valve to make the brakes effective when cold , they will lock up FOR SURE if run at a competitive event where they see heat. "Street driving " is not enough.
   In drag racing , I ride the brakes when smoking the tires before the starting line. The holding power on the starting line is far better with the rear brakes heated and stopping at the end in great too.

[shelbydoug]

  The valves were set to work with "hot" brakes. If you set the valve to make the brakes effective when cold , they will lock up FOR SURE if run at a competitive event where they see heat. "Street driving " is not enough.
   In drag racing , I ride the brakes when smoking the tires before the starting line. The holding power on the starting line is far better with the rear brakes heated and stopping at the end in great too.

Aren't the valves overkill on the street then? They should be R model only then?

[Royce Peterson]

No, they were used on every Mustang. Not Shelby installed or specific. Totally needed on any disc brake equipped car of any make or model if you have a disc / drum combination.

  The valves were set to work with "hot" brakes. If you set the valve to make the brakes effective when cold , they will lock up FOR SURE if run at a competitive event where they see heat. "Street driving " is not enough.
   In drag racing , I ride the brakes when smoking the tires before the starting line. The holding power on the starting line is far better with the rear brakes heated and stopping at the end in great too.

Aren't the valves overkill on the street then? They should be R model only then?