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The always helpful Joe P. turned me on to the mid 60's Cadillac MC upgrade. Should bolt right in, hopefully. A small amount of re-plumbing required. Check out this thread:
The always helpful Joe P. turned me on to the mid 60's Cadillac MC upgrade. Should bolt right in, hopefully. A small amount of re-plumbing required. Check out this thread:
that was my plan mc to use. Just not sure how to get the juice to the wheels
Seems pretty straightforward to me. Remove the rear brake line connection from the distribution block and plug it at the block. Bend the rear line over a bit and make up a new line that goes from the new master cylinder to where the rear brake line connection is. Use a coupler to connect the two flared connections. You'll have to make up a new line for the front brakes from the master cylinder to the distribution block as well. Bleed it out and you should be done.
I think the only tricky part would be getting the rear line bent just right to meet up with your new line. I did also notice that the new MC takes 1/2" fittings, so that will be a bit fiddly getting everything you need.
Last edited by ourkid2000; November 7th, 2023 at 02:40 PM.
Does the post-66 toro with dual master have a brake warning light wire connected to a distribution block? I am considering adding a block with this feature while doing the plumbing for the new master. Its purpose is to illuminate your brake warning light if one of the two circuits has a pressure drop relative to the other. I'm not paranoid about the brakes, just figured while I am poking around the plumbing I'd look into this.
Does the post-66 toro with dual master have a brake warning light wire connected to a distribution block? I am considering adding a block with this feature while doing the plumbing for the new master. Its purpose is to illuminate your brake warning light if one of the two circuits has a pressure drop relative to the other. I'm not paranoid about the brakes, just figured while I am poking around the plumbing I'd look into this.
Yes, the warning light was part of the federal requirement that mandated dual circuit brake systems for the 1967 model year.
Does the post-66 toro with dual master have a brake warning light wire connected to a distribution block? I am considering adding a block with this feature while doing the plumbing for the new master. Its purpose is to illuminate your brake warning light if one of the two circuits has a pressure drop relative to the other. I'm not paranoid about the brakes, just figured while I am poking around the plumbing I'd look into this.
Note that the 1967 cars are among the very few ever built that actually DO use a proportioning valve with a four wheel drum brake system. The device located in the line to the rear brakes (arrow B in the drawing) is the proportioning valve. 1966 cars did not use this. Again, the requirement is to prevent premature rear wheel lockup under panic braking. There are multiple ways to accomplish this; the prop valve (which reduces hydraulic pressure to the rear wheels) is only one of those ways. Master cylinder bore, wheel cylinder bore, and tire specs also all effect this. The prop valve is only correct for factory conditions (brakes, tires, etc). Any changes from stock and all bets are off on prop valve calibration.
Note that the 1967 cars are among the very few ever built that actually DO use a proportioning valve with a four wheel drum brake system. The device located in the line to the rear brakes (arrow B in the drawing) is the proportioning valve. 1966 cars did not use this. Again, the requirement is to prevent premature rear wheel lockup under panic braking. There are multiple ways to accomplish this; the prop valve (which reduces hydraulic pressure to the rear wheels) is only one of those ways. Master cylinder bore, wheel cylinder bore, and tire specs also all effect this. The prop valve is only correct for factory conditions (brakes, tires, etc). Any changes from stock and all bets are off on prop valve calibration.
So it sounds like I should probably be more interested in the proportioning valve than in a warning light, from a braking standpoint.
This raises questions:
Do the 66 brakes lock up the rears prematurely as delivered?
Would separating the front and rear circuits make them more likely to prematurely lock and now necessitate a prop valve?
Comparing the part numbers for replacement shoes, drums, and cylinders between 66 and 67...
Perhaps I am overthinking this. I'm trying to wrap my brain around a couple questions:
1) whether a drum+drum 67 using the prop valve is fixing a deficiency found in the 66.
2) whether going to dual MC on 66 would create a need for a prop valve.
I feel like this info should help draw some conclusions. Does it?
At this point I think I'm just looking to convince myself that putting the dual mc on my 66 and routing the lines (without any additional gadgets) is not creating a new problem, so I can move forward.
SHOES
DRUMS
CYLINDERS
Last edited by mike 66 toro; November 15th, 2023 at 06:59 PM.
Your first mistake is assuming that RockAuto listings have any basis in reality. These are the same folks who claim that 11x2" drum shoes are correct for the 1961-63 F85/Skylark cars.
The single vs dual M/C has nothing to do with the need for a prop valve if the piston diameters are the same. A very few GM cars used M/Cs with different diameter pistons for front and back circuits, but that was in the 1980s and later. Again, the use of a prop valve is simply to balance front and rear braking force, primarily under panic stop conditions where the front bumper dives, unloading the rear brakes. If the rear locks up, you can lose directional control. Of course, if drivers were capable of sensing impending wheel lockup and modulating pressure on the brake pedal as a result, this wouldn't be necessary, but that skill is beyond the capabilities of most drivers.
The single vs dual M/C has nothing to do with the need for a prop valve if the piston diameters are the same
Sounds good, I'll plumb it in nice and simply, and maybe some time in the future test a hard stop on some sand, to see if the balance is acceptable. If it was bad on sand, then I know I'd definitely have a huge problem on pavement. It's something at least.... I know that wont simulate a true panic stop on pavement, but my very defensive driving style with my classics does not necessitate locking up the brakes.
Edit:
I see Fusick shows the brake parts are same for 66-67. So Olds switched to dual MC in 67 for drum+drum, without other brake hardware changes that would affect balance?, but they decided to add the prop valve... Hmmm. Perhaps getting the 67 prop valve is possible?
Last edited by mike 66 toro; November 16th, 2023 at 07:07 AM.
November 7th, 2023, 06:37 AM
