brake proportioning valves questions

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moparmat2000

moparmat2000

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hi y'all

need an answer to a question. i got a 67 cuda, but the body is 67 cuda, everything underneath is going to be 74 dart. i am using the big disc brakes off the front of a cordoba, and the big drums off the rear of a cordoba. i have the large bore cordoba master cylinder, and just ordered my brakeline kit for a 74 duster from inline tube. i was told this car was a 108" wheelbase like my cuda is. anyway. i have the stock drum brake proportioning valve from the old cuda brakeline system, and i have the proportioning valve from the 74 dodge dart donor car

can i use the dart proportioning valve with the bigger cordoba brakes? should i try to find a cordoba proportioning valve? could i even use the old barracuda 4 wheel drum proportioning valve? id like to use the right one, and only have to bleed the system once.

thanks in advance
matt
 
A drum/drum car has no proportioning valve. Which makes me think you are talking about the junction box/safety switch. Which, in a 1974 disk brake car, includes the proportioning valve. But in a 1968 car, the PV was plumbed in separately on the rear line, so the junction box/safety switch would not have a PV either way.

In any case, the proportioning valve isn't really affected by the master cylinder size.
 
MoparMatt, I'm confused. Do I understand that you intend to use "Dart" lines on a '67 Cuda? It depends on how one defines "Dart". By the '74 model year, "Dart" and "Dart Custom" referred to the 4-door sedan.

Actually the Dart 4-door sedan and the Swinger 2-door hardtop were on the 111 inch wheelbase. The Dart Sport (Duster twin) were on the 108 inch wheelbase.
 
2 Darts said:
MoparMatt, I'm confused. Do I understand that you intend to use "Dart" lines on a '67 Cuda? It depends on how one defines "Dart". By the '74 model year, "Dart" and "Dart Custom" referred to the 4-door sedan.

Actually the Dart 4-door sedan and the Swinger 2-door hardtop were on the 111 inch wheelbase. The Dart Sport (Duster twin) were on the 108 inch wheelbase.
Click to expand...

Yes i am using all the mechanicals and suspension from a 74 dart donor in my 67 cuda body shell. I used the larger cordoba brakes on the front 74 dart spindles, and the rear cordoba brakes on a 8.75 rear axle. also using the larger bore cordoba master cylinder.I ordered a set of brakelines for a 74 duster, 108" wheelbase because my 67 cuda is 108" wheelbase, as well but my brakes from the 74 dart have more in common with the the 74 dart/duster than with a 67 cuda.if that makes sense.
 
Thanks for clearing that up. Plan sounds good. I've done several BBP disk brake conversions. You'll enjoy the extra stopping power and the security of having steady brakes on those rare days when it rains in west Texas (not West, Texas).

To answer your original question, the Cordoba valve ought to work. The balance may not be quite right, but it was a compromise at best anyway. There is a big weight difference between a Cordoba and a '67 Cuda. The weight balance F/R as a % ought be close. I think I'd be comfortable with it.

The design is to get the fronts to lock up first. When the rears lock first, the tail wags the dog. Don't believe it, watch NASCAR on a road course. When a guy dials up to much rear brake, the rear starts hopping and the car goes towards the weeds tail first.
 
2 Darts said:
Thanks for clearing that up. Plan sounds good. I've done several BBP disk brake conversions. You'll enjoy the extra stopping power and the security of having steady brakes on those rare days when it rains in west Texas (not West, Texas).
Click to expand...

Having one of those rare days today as a matter of fact. Playing Mr Mom today, while mom is sleeping. She works weekend nights at a rehab center. Not gonna end well today i can see it already, my 6 and 7 year old are already at it with each other, and we are stuck in this house. When mom wakes up, im going to my garage and unwinding.
 
I agree to using the 74 proportioning valve. As said, the fixed ratio the factory used is an estimate. Once you change brake parts (rotor diameter, pad type), tires, or weight distribution, the ideal ratio changes. An adjustable proportioning valve allows you to dial it in (in a wet parking lot), but that wasn't a factory option. You can get new ones <$30, but you probably want the whole sheebang, w/ distribution block, imbalance switch, and front hold-off valve. Those cost ~$100 aftermarket. However, the factory valve you have is probably close enough.
 
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