ddsjoseph

I have a 1965, with manual brakes and dont know if I can convert it to power brakes by adding a power booster. The car had a body off restoration in the early 90's but I am not sure if they changed the brake lines. The front brake lines appear to be in good clean condition. Would I need a proportioning valve as well, since they are all 4 disc brakes? I am not even sure if I should replace all for brakes with Stainless Steel brakes since the calipers on my original are a bit sticky and at high spees the car pulls to the right when braking. Cost is not an issue since this is a safty matter. Please help.
Thanx

CaveCreekChump

I made this improvement on my '65 Roadster last December and the resultant brake function has been impressive. Bought everything from Corvette America, but I am sure all of the major players have good stuff. I basically added a booster and changed the master cylinder to a dual chamber - turned the whole thing into a '67, brake-wise.

Yes, a proportioning valve mounted at the master cylinder is a must. If you go with a dual master cylinder, you must run a separate line to the front brakes as well as the existing line to the rear brakes. The p-valve will ensure that the controlibility of the car in a panic stop is not compromised.

Good luck!

CaveCreekChump

The sticky caliper problem should be addressed at the same time, to ensure reliability of operation. After examination, you may find it desireable to replace them with new calipers that have been sleeved with stainless steel.

Moisture absorbed into brake fluid may have damaged the walls of the piston cylinders, causing several problems.

I have done the replacement and now use Dot-5 fluid which will not absorb moisture.

JohnZ

Disc-brake Corvettes don't use proportioning valves - that function is handled by the design of the hydraulic system, via smaller pistons in the rear calipers. The only time you need a proportioning valve is when you add front disc brakes to a '63 or '64 and leave the drum brakes on the rear.

CaveCreekChump

I sort of thought the same thing myself, but then I talked to a guy I thought was pretty knowledgable who convinced me otherwise.

Want to buy a slightly used proportioning valve?

70vert

I changed my 65 master to a dual mc. No "proportioning" valve needed. I used a combination of 65 and 67 brake lines and blocks. The mc was a new one from Napa I got for about $30. I have manual brakes (no boster) and like the pedal feel.

Plan B

I think there were a lot power brake units sold for the 65 with a proportioning valve. Not knowing any better, I was one that bought the package. My car is in the middle of several projects and I have not really road tested the brakes completely. Is there a problem if I leave the P valve in? I've only really drove the car in the driveway and it doesn't seam like it wants to stop on a dime. Is the P valve a possible culprit?

Thanks,
b

CaveCreekChump

My power brake conversion works great, even with the apparently unnecessary prop valve.

JohnZ

A lot of folks confuse the terminology - if you're talking about the block in the photo below, that's NOT a proportioning valve - it has no valve function at all; it's the "distribution block", and its only function is to contain the differential pressure warning switch that lights the "Brake" warning light in the cluster.

Road machine

Extreme caution should be used when initialy setting a proportioning valve. If the valve is set for too much bias toward the back you could lock up the rear and loose control. Too much front proportion will only increase stopping distance but will not make you loose control. The valve over time could wear and cause more brake to the rear, so if you do have a proportioning valve check your bias often by making an emergency stop somewhere that is safe if the rear locks up.

deanoshiro

This type of proportional valves produced today are JUNK, made for one size fits all and they sell it a universal fit. Be it a Model A or a Lincoln they sell the same prop valves. Nice job explaining this JohnZ.

Plan B

Whoa... I guess I am confused. I don't have a P valve I have a distribution block? So now where's the wire that goes to the pressure warning switch?

Thanks
b

CaveCreekChump

Based on my results, I would recommend that he convert to a safer and more functional brake system by adding a vacuum booster and dual chamber master cylinder.

Plumb it appropiately and forget about adding a proportioning valve. If your experience is the same as mine, you will be impressed with the improvement in brake function.

(BTW, I am not talking about a junction block mounted on the frame. The prop valve I have hangs from the master cylinder)

deanoshiro

If your car came with a factory distribution block your are fine. It was "engineered" for your specific car. It may or may not have the rear brake system "metered". I am referring to the distribution/proportional blocks/valves sold today as "universal" and one application fits "all"

Sorry to confuse you.
dso

JohnZ

The distribution block (and the tan wire that connects to it) didn't start until 1967; the outlets on the dual-circuit master cylinders used on 65's and 66's with power brakes were plumbed directly to the front and rear systems. The only application that used a real "proportioning valve" for the rear system was the J56 Heavy Duty Brakes option in '66 and '67.

Plan B

John you are just too good!

Thanks,
b

johns_vette

I have been following this thread and there are a few open items that would be of great info to me and hopefully others.

One the boosters - I see those out there for a little under $200. Is that the booster people are using?

The master cylinder - what one do you use to convert to a dual line? Can a 67 dual master cylinder be used with one of those boosters?

Finally, Once we get the junction block in place we are good to go?

I was very happy to see this post because I called one of the vendors before JohnZ answered about the valve. They told me the exact same thing that I would need one and I just could not understand because I did not see one on other midyear cars with power brakes.

CaveCreekChump

I used #42092 booster with master cylinder (around $400) and #42470 boot for around $10.

The booster already has the grommet and checkvalve assembled to it.

keri45

Since my 66 Roadster Had no Tank Sticker and the Repo Window Sticker is not of that much insight and info that can be authenticated., would it influence the value on a (Off Body Restored 427/390 with Factory AC and Factory Power Steering #s Matching to VIN and Trim.) ??
2nd ? Too much for me to handle so any suggestions as to Who is Capable of not screwing this up. I dont mind going to a Classic Car Restoration Facility but its far away,, thus do you think if I were to supply the Correct Parts Booster Fittings and Dual MC and associated parts from a Vendor that uses GM Restoration Parts that like a Chain Service Facility i.e Firestone ,or Brakes Plus or a Garage Small Time Station Mechanic could do this or dont take a chance Theyll screw it up... I mean how hard can it be if you have Brake Bleeders and Correct Tools to service brakes? Perhaps beyong the cap[ability of those types of stations...Thoughts as to how many hours do do that job and the difficulty for an average Maechanic.?? thanks?