Topic: '65-'66 Proportioning Valve Rebuild Help

[GlennG]

I decided to rebuild my proportioning valve in my '66 Shelby.  It was very cruddy-looking when I pulled off the attaching brake lines.  I'm not surprised about this, since my car has probably not been running since the late 1970's. Anyway, I found a website (http://www.stangerssite.com/brakevalve.html) that talks about rebuilding the Kelsey Hayes '65-'66 proportioning valve.  But what it fails to mention is this.  Once you take it apart and hone it and replace the seals (seal kits are available for around $25), you can put it back together, and reset the adjusting nut and sleeve.  Of course, I am assuming that the inside bore of my proportioning valve is not badly pitted, and that I can successfully hone it.  You are supposed to set this adjusting nut and sleeve back to a measurement that was taken before you take the proportioning valve apart.

But then I was wondering, there must be specs. for the brake line pressure for the front calipers and the rear drum brakes.  I have a Snap-On ABS brake pressure testing kit.  When I hook up a brake line pressure gauge to the front disk brake line, and then hook up another pressure gauge to the rear drum brake line, I can read the specific pressure of both disk brake and drums.  I would like to fine-tune my proportioning valve to the ideal line pressure from front to rear.  My rear drum brakes have been rebuilt with stock brake linings...nothing special.  I have rebuilt my front KH disc brakes myself using basic brake pads and stainless steel piston replacements.  So, my question is this: 

WHAT IS THE IDEAL BRAKE LINE FRONT AND REAR PRESSURES- FOR A '65-'66 MUSTANG OR SHELBY WITH FACTORY FRONT DISC BRAKES AND REAR DRUM BRAKES?  Any ideas on this would be much appreciated.

[s2ms]

Hi Glenn,

I tried to rebuild the original prop valve in 6S1757 myself but it didn't work so had to have it professionally resleeved/rebuilt.  I did not hone it, because it didn't appear to needed it (bad move), but you may have more success if you do.  Everything looked good until the rear brakes locked up on a test drive, after getting the car home I never could get them to return properly.  I think the problem was some micro-scoring from when I removed the piston.  They were too small to notice but affected the operation when it was reassembled.  I'm not discouraging you from trying it yourself, just passing on my experience as a heads-up.  Even if it doesn't work you can have it resleeved later...

Sorry I can't help on the pressure question, something I've always wanted to know myself.  What complicates things is the add/delete sheets for 65-66 GT350's show they actually had a different Ford part# prop valve than non-Shelby disc brake cars.  Since the valves all appear the same I assume the Shelby valve was different in the pressure bias setting to account for the metallic rear shoes and larger drums.  I'd sure like to know if anyone has more info on this...

Dave   

[MWM]

Glen and Dave,
 I too would like to know the ratio of front to back to get optimum performance. I did not rebuild my proportion valve, but sent it to White Post Restoration. http://www.whitepost.com/
Perhaps calling and asking for WR can help you in your research. I know that I supplied a lot of information prior to the rebuild such as front disc size and rear drum size to help them set it up. I simply bolted it in, bled and it has been performing great for seven plus years including track time.
Good Luck!

[s2ms]

Glen and Dave,
 I too would like to know the ratio of front to back to get optimum performance. I did not rebuild my proportion valve, but sent it to White Post Restoration. http://www.whitepost.com/
Perhaps calling and asking for WR can help you in your research. I know that I supplied a lot of information prior to the rebuild such as front disc size and rear drum size to help them set it up. I simply bolted it in, bled and it has been performing great for seven plus years including track time.
Good Luck!

White Post was who I also had resleeve/rebuild my prop valve after the self rebuild attempt failed. That was about 7-8 years ago as well, it has also perfomed great. I think I only told them it was for a 66 GT350 but have no idea if they used that info for the adjustment.

Good idea about asking them how they adjust these!

Dave

[J_Speegle]

Below are a couple of resources that might help. Remember we share the valve with the early Corvette so you can follow that lead

Hope this helps a bit


http://www.stangerssite.com/brakevalve.html

http://forums.corvetteforum.com/c1-and-c2-corvettes/2615892-1966-j56-proportioning-valve-question.html

[Texas Swede]

If I don't recall wrong, there should be 11 treads visable when the nut has been tightened
to give the correct pressure. That's what mine had before rebuild and now after rebuild.
Texas Swede

[sgl66]

Had my valve rebuilt and would like to replace jam nut. I can only find 1/2 inch thick. Do the correct 1/8 thick exist anywhere?