70vert

I feel uncomfortable with my '65 single master cylinder (manual). I have read where people are converting these to a dual setup.
Should I use a '67 setup? I will be replacing all components that ever see brake fluid. If I use a '67, I realize the brake line will run on the side of the frame rail, front to back; how big of a crime is this on an #'s matching FI car? Also, any problems changing from the 3/16" lines to 1/4" lines? Is there any fitment issues with the distribution blocks, mainly the rear one. Is the bracket that holds the rear distribution block in the same loacation on a '65 and '67; or will I have to weld a new on to make it work. Finally, are there any other concerns that I should have.

Thanks in advance

stingrayl76

#'s matching fuelie and you are thinking about using the 67 M/C?
Purists may have a problem with that, but it's your Vette and do it the way you want it.
To make it totally correct you would have to use the 65 power brake M/C, and 3/16 lines. To make it totally correct were talking a lot of $$$$. An original 65/66 M/C alone is upwards of $1K vs. the 67 which is under $200.00. If you are not going to have it judged and are just concerned about the safety aspect because you plan on driving it, I would use the 67 set up, although I would suggest adding the booster. Unless a person looking under the hood of your Vette knows Corvettes, they won't be able to tell whether or not it is correct anyhow.

As far as running the lines if you use 1/4 lines you have to change the front and rear distribution blocks which should not be a problem. Forum member Corbrastang just went through this drill a couple of months ago. Maybe he can instill a little wisdom here.
Here is his Thread on the subject:
http://forums.corvetteforum.com/show....php?t=1375928

You are going to get a lot of opinions on this subject, but it's your Vette and do what makes you happy.
Dave

70vert

Thanks for the reply. I have seen that post as I usually check the archives before posting.
While I will probably never have this car judged, I want to keep it original EXCEPT for bolt on stuff that can be changed back to original farily easy. I don't want to spend $1000 for a MC, and I like the feel of manual brakes.
So, I would have to fasten the '67 brake line somehow to the frame. I think this requires two holes (maybe three) for the brake line clip screw. Or, should I figure out a way to fix the brake line to the frame without drilling holes.
The big question for me is the rear distribution block bracket. Does anyone know if it would have to be modified or changed?

MikeM

Some '65's had a 3/16 line to the rear and some had 1/4. If you change the line, you'll have to change the rear block. Changing the line and doing it like factory on a '65 will require lifting the body on the left side. Other years vary.

A dual master cylinder is not insurance against losing your brakes due to a sudden, major leak. I've lost brakes twice on vehicles with the dual system and once with the single. In all three cases, the brake pedal went right straight to the floor when a main front/rear brake line let loose (corrosion) on two of them and I can't remember on the third.

On a mid year Corvette, the best insurance I've seen against sudden catastrophic brake loss is to make sure your main front/rear line is in good condition. If it's never been replaced, it probably should be even if your car has been stored inside and driven very little as mine was.

woodsdesign

I did this exact change on my 65. As mentioned, you will have to change the distrubition blocks. You will also have to drill holes in your frame for the line clamps. Also, I found that I had to enlarge the "v" space where the transmission cross member is welded to the frame.
(This may not be the case for all cars) I also added the 67 proportioning valve. You will not have the wire that goes to the light on the 67. I did it for two reasons. First: my lines were rusty and I didn't want to do a body off. Second: Safety. I feel it is a good way to improve your safety without having to do a body off.

Larry

Kensmith

Just a note about dual masters. My son has a 2001 S-10 extreme with anti-lock brakes. The truck was lowered by bubba and the r-front brake line had been wearing against the control arm as it was mounted 180 degrees backward. Well, he had a lady cut him off and hit the brakes and you can guess for sure the r-front brake line blew. Brake pedal to the floor, and very close to a bad accident but my son was able to swerve and avoid several cars. I went to see if I could limp it home as he was only a mile away and there was nothing left to the pedal no matter how many times I tried to pump it. So I am not a firm believer in dual master cylinders. As previously stated, if you check you lines and all in good order, you should not have any problems.

adrenaline-guy

I recently did the conversion on my 65 but found that I needed a power brake booster to deal with the rock-hard pedal from the dual MC. Could be because I used the 1965 power brake lines from Long Island Corvette that were 1/4"...? I think I also ended up with an interchangeable power brake and manual brake master cylinder from LICS. Who knows? It works now.

BamaZR1

Does a '67 Corvette with manual brakes (dual MC) use any form of proportioning valve, combination valve, metering valve, etc? OR are the front and rear brake line circuits plumbed directly to the MC itself?

rayL79

No proportioning valve. That block by the master cylinder is just a sensor for the dash "brake" light.

larrywalk

Years ago, I replaced my '65 single master cylinder (manual brakes) to the '67 dual master cylinder for manual brakes. It was a great change and gave me more assurance that a leak in the front or rear wouldn't cause a total loss of brakes - I had had this happen twice before!

Some considerations:
1. Ensure that bore of the master cylinder is the same as that of the '65 master cylinder to keep the same pedal feel. IRRC, mine was 1".
2. I did not use the so called "proportioning valve" because it isn't really a proportioning valve - it is only a differential pressure block to close a ground if the pressure on one side differs from the other, in other words, it can light a light to let the clueless driver know that half his brakes are going bad.
3. No need to change the size of the tubing going forward or rearward - just split the front circuit from the rear circuit and use adapter fittings to connect to the MC. FWIW, I connected the rear circuit to the front half of the MC; and the front circuit to the rear of the MC for ease of plumbing connections - others have done it the other way, but there was no difference to the feel of the brakes in either gentle or hard braking.