dual bowl master cylinder - Impala Tech
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post #1 of 12 (permalink) Old 10-08-2015, 07:59 AM Thread Starter
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dual bowl master cylinder

I want to r & r my drum brakes on my 66 ss. After 66, did GM go to a dual bowl master cylinder with drum brakes? I have power assist drums, but with a single bowl cylinder, and if I get a dual bowl with attached proportioning valve, I will need lines from where the existing valve is on the frame(at least I think it's a proportioning valve) to the new master cylinder. If, let's say, in 67 GM used dual bowls, then the lines I would need would be used. Thanks for any info and enlightenment!
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post #2 of 12 (permalink) Old 10-08-2015, 08:11 AM
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A '67 dual bowl is a direct fit. Only a car fitted with front discs needs a proportioning valve, the rest just use a frame mounted distribution block. The correct lines are widely available or you can make your own. But if you make them try to use lines already flared (obviously with fittings already on) as trying to get a good sealing double flare with an inexpensive flaring tool was always a challenge for me.

Mike

1965 Impala SS 396
1967 SS427
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post #3 of 12 (permalink) Old 10-11-2015, 04:03 PM Thread Starter
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Michael, appreciate the info. I'm confused about the distribution block. if I get a dual bowl for a 67, do I also look for a dist. block, as I will have more lines now? and to get the correct lines from the bowl to the block, I would look for 67 lines, as now I have a single line. Am I correct, or am I lost out there somewhere?? lol
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post #4 of 12 (permalink) Old 10-11-2015, 06:07 PM
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You mount the new 67 drum/drum master. You run the rear line to a T, that splits to the front wheels. The front line now goes to the line that runs to the rear wheels.

Two doors, four doors, wagons, and ragtops.
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post #5 of 12 (permalink) Old 10-11-2015, 08:44 PM
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Between the front and the now separate rear lines there is a brass distribution block that contains a spring mounted spool valve. So long as the line pressure in both lines remain the same nothing happens. If you loose pressure in the front system or the rear then that perfectly balanced spool valve moves tripping the brake warning light on the dash (same one used for e-brake being left on), and the spool valve moves toward the side with the lower pressure to allow fluid from the higher side system to safely stop the car; at least once.

That switch stays in the brake light on position until bleeding the brake pushes it back when you complete the repair.

Big Dave
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post #6 of 12 (permalink) Old 10-13-2015, 08:50 AM
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Look for an used '67-68 distribution block to replace your current one line block. There are no wear parts, so used will be fine, as long as none of the threads are messed up.

Buy a dual res master for Drum/Drum, but make certain it has the internal residual valves to hold pressure on the wheel cylinder cups. If it doesn't, you will need in-line valves. I usually go to NAPA for these as a first choice. The remans are very good. Then buy prebent or make the lines to connect it all up. As long as you are this far in, may as well replace the wheel cylinders with new too.

On the subject of making brake lines, there is a high copper alloy tubing that flares and bends much easier than the steel tube. It is easily formed by hand with little risk of kinking. Steel tubing is very difficult to get a leak free flare with the cheap hand held tool, and is prone to kinking when bent by hand. A forming tool helps.

This is the copper alloy tubing, hand formed. The tighter bends were made with a forming tool for appearance.



'62 Impala SS 409 TH350
'66 Chevelle SS 496 M20
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'67 Camaro ss/rs 350 PG
'38 Chev coupe street rod
'54 Chev 210 2 door
'69 Chev C10
'89 Chev R3500 roll back
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post #7 of 12 (permalink) Old 03-09-2016, 08:48 AM
 
 
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I have a similar question about my '64. It has 4-wheel drums and factory power brakes. I got a new power booster because the old one failed, only to find that the factory single-reservoir master cylinder is leaking. I want to convert to a dual reservoir. I see conversion kits online for 4-wheel drum cars that come with pre-bent lines and a distribution block. BUT, they say for manual brakes. Can this kit be used on a power brake car? Is there a difference in MCs between power and manual?
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post #8 of 12 (permalink) Old 03-09-2016, 09:04 AM
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Quote:
Originally Posted by turbojimmy View Post
I have a similar question about my '64. It has 4-wheel drums and factory power brakes. I got a new power booster because the old one failed, only to find that the factory single-reservoir master cylinder is leaking. I want to convert to a dual reservoir. I see conversion kits online for 4-wheel drum cars that come with pre-bent lines and a distribution block. BUT, they say for manual brakes. Can this kit be used on a power brake car? Is there a difference in MCs between power and manual?
Master is the same. The actuator rod between the booster and mc will be a different length. Some conversion kits come with both rods or the longer rod should available from the same source. The lines from the mc to distribution block will be short because the master is located forward of the firewall by the booster. You MAY be able to make them work, but you might have to get longer lines to connect the mc and block from a local source.

'62 Impala SS 409 TH350
'66 Chevelle SS 496 M20
'70 Chevelle SS 396 M20
'67 Camaro ss/rs 350 PG
'38 Chev coupe street rod
'54 Chev 210 2 door
'69 Chev C10
'89 Chev R3500 roll back
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post #9 of 12 (permalink) Old 03-09-2016, 09:18 AM
 
 
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Quote:
Originally Posted by Lost in the 60's View Post
Master is the same. The actuator rod between the booster and mc will be a different length. Some conversion kits come with both rods or the longer rod should available from the same source. The lines from the mc to distribution block will be short because the master is located forward of the firewall by the booster. You MAY be able to make them work, but you might have to get longer lines to connect the mc and block from a local source.
Thanks! The new booster appears to have come with some sort of extension rod. I didn't look at it closely. Good point on the lines - they will be the right length for an MC mounted directly to the firewall. I'll see what I can rig up. In the meantime I'm going to order the manual, 4-wheel drum MC kit.
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post #10 of 12 (permalink) Old 03-18-2016, 09:08 AM
 
 
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If anyone is interested, here is what I did....

I ordered Late Great Chevy (Eckler's) dual-reservoir conversion kit. They only listed one for manual, drum brakes. As described in the posts above, the lines that came in the kit will require some tweaking to work with my factory power brake '64. The kit is nice and contains all the lines, proportioning valve and a nice bracket for the valve that uses the MC's mounting studs.

The kit came with a manual brake MC, too. As pointed out above, the power-brake rod from the booster is going to be too short. I figured I would make that up somehow. BUT, I also learned that the bore on the MC cylinder is bigger on a manual MC to create more pressure. So I decided to exchange the manual MC for a dual-reservoir, power-brake MC. It was only $4 more, but I had to pay return shipping on the other one so I wish I had caught that up front.

In retrospect, I should have just gotten the whole shootin' match. It would have been cheaper to buy a manual-to-power conversion kit that came with the booster, MC and lines. BUT, at the time I bought my booster I didn't realize the MC was bad as well. So I bought a kit without the booster.

Now I have a pile of new parts to install!
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post #11 of 12 (permalink) Old 03-18-2016, 06:37 PM
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Do not use copper tube for brake lines. Its not D.O.T approved, and its unsafe. And its illegal. Dont risk your friends, family or your life using copper for brake lines. I just bought a parts car that had copper brake lines. Glad it off the road.
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post #12 of 12 (permalink) Old 03-18-2016, 07:52 PM
 
 
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Quote:
Originally Posted by dadstoy View Post
Do not use copper tube for brake lines. Its not D.O.T approved, and its unsafe. And its illegal. Dont risk your friends, family or your life using copper for brake lines. I just bought a parts car that had copper brake lines. Glad it off the road.
Mine are all steel - both old and new. With the price of copper these days I don't know why anyone would use copper over steel!
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