Single master cylinder episode

[Tom Kochtanek]

How odd is this?

Today I zip down to the local parts store to pick up some brake hoses, fittings, and line to fabricate up the newly installed dual master cylinder in the 1962 SS. You know, the thing you are supposed to do when you restore you car for daily driving, providing more safety in brake operations. So I drive the '63 Corvette down to pick them up. Pulling in to the parking area, I feel a softness in the pedal. So I pick up the parts and get a can of brake fluid as well. Checking the single master cylinder (I broke rule #1 when I restored her 5-6 years ago, not converting over to the dual master cylinder) I note she is down about a quarter inch, so I top it up, vowing to check closer when I get home (1 mile). I am in downtown Columbia, near the University, and it is lunchtime -- lots of cars in a hurry.

Well, you can guess that my brakes gave out two stop signs later and I had to use the emergency brake along with using engine decompression to stop me :(. I pulled safely into a parking lot and called for a tow. Went straight to the shop where I was headed to work on the '62 SS. Now I have them both together, neither one stops, but at least the Corvette starts. The lighting is pretty poor, but you get the picture. Now I have two sets of dual master cylinders that I need to convert over to :) :) :).

I'm just glad I didn't hit or hurt anyone!

I also included a shot of the posi mounted with the 4 link rear suspension. We have the engine and transmission installed, working on those brake lines, new gas tank, fuel line and sending unit installed. Need to cut a hole for the 4 speed, connect the drive shaft, send her off for an exhaust, then lose sleep for a while until I get to hear her fire up :). That will come later next week (assuming all goes well) when I return from being out of town!

Cheers,
TomK

[threeimpalas]

Good to hear you got it stopped without incident. I've had the front brake circuit on a dual system go out before, and that's enough of a disconserting feeling for me. Can't imagine how intense it'd be to lose all four wheels.

[walkerheaders]

Gosh Tom, those are the nicest cars....................:bow

[bobs409]

Don't always count on those dual masters to stop you either. My 72 Malibu blew out a line under the driver floor area and there was absolutely no pedal! I too had to use the emergency brake or I would have went right through a busy intersection! :eek:

[chevymusclecars]

Tom

In this conversion to a dual master cylinder are you using a metering block like would have come on an original system. It is my understanding that the metering block actually was used to apply more even pressure to all wheels during braking and in the event of failure a small ball acts as a check valve to block the end that has a failure. The block also makes for a simple jucntion block to connect the lines. If you do go with the block the ones for drum brake and front disc brake cars are different orfice sizes internally.

Bill

[Tom Kochtanek]

Bill:

No, I was not aware of such a device. I have the fronts mocked up (not yet operational) directly from one of the 5/16 outlets on the dual master, the rears on the other. Sounds like I might need to consider that. Any recommendations about which orifice works for my application, and where I might locate such a block?

Thanks!
TomK

[chevymusclecars]

Tom

You can make a run to the junk yard and pick it up off any model car that the attached mounting bracket looks like an easy fit for your car. If you see an early car with drum brakes that is the one I would use. All of the GM cars used the block so it should be easy to find.

Bill

[JimKwiatkowski]

Tom,if you have ft disk brakes you need a proportioning vavle.Go to search and type in dual master,alot of good info written on this subject.

[gearhead409]

all gm four wheel drum brake, dual master cyl. cars don't have a metering/proportioning valve.the extra block everyone is talking about is a switch only on these cars, it alerts you to a failure in the system. on the front disc./rear drum cars this extra block does have a metering valve to the front brakes and a proportioning valve to the back brakes. the proportioning valve is sometimes a separate block on the early cars.

[SteveD409]

Some early drum/disc GM systems used a golf ball size apperatus that just slightly delayed the pressure to the rear, didn't change the pressure.

[gearhead409]

that's correct Steve. the early disc brake cars were kind of crude by today's standards.

[chevymusclecars]

I have a 67 Chevelle SS and the disc brakes are four piston calipers similar to what was used on the Corvette. These brakes use a seperate proportioning valve that mounts between the metering block and master cylinder. This method was used between 67 & 70, in 71 the proportioning valve was incorporated into the metering block. The metering block on the drum and disc brake cars was different for even the earlier years that used a seperate proportioning valve which i believe was because on the size of the internal orfices.

Bill

[jester]

Bill:

No, I was not aware of such a device. I have the fronts mocked up (not yet operational) directly from one of the 5/16 outlets on the dual master, the rears on the other. Sounds like I might need to consider that. Any recommendations about which orifice works for my application, and where I might locate such a block?

Thanks!
TomK You should visit MP brake's web site . They have alot of pictures and drawings of brake systems in their tech section.

[gearhead409]

this company is one of the best aftermarket/streetrod brake companies out there. they can and will answer any brake question,supply any part or complete kits for your older car. i have installed a number of their complete kits on customer cars and you do not have to buy any extra parts. every nut, bolt, new brake lines are in the kit. nice people to work with.

[Tom Kochtanek]

Thanks for all the advise! I was able to finish the brake setup for the front pair of drums, but needed some more time to fab up the rear lines, as they were not part of the kit. No offense to these kit makers, but while the brake kit was a pretty good fit, the fuel line was not even close. I think the guy who bent them was either dyslexic or left handed (I am left handed as well) :).

Made some more progress today, cut the hole out for the 4 speed and installed the drive shaft. I went with that billet piece everyone was raving about. Here's a shot of the floor boards being prepped for that four speed :).

Cheers!
TomK

[gearhead409]

Tom,your going to love this car!