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1970 Cuda brake questions #3001166
01/02/22 03:47 PM
01/02/22 03:47 PM
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cdstl Offline OP
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Ok, here goes.

Disc brake car. I understand that there is a Distribution block and a rear hold off block. I also see that Inline tube sells a 3 port hold off block.

A disc brake car needs the Distribution block, obviously, and I would imagine the rear hold off block. Does the rear hold off block limit the brake pressure to the rear brakes? Do you combine the 3 port hold off block in there anywhere?

I have an FSM and I've looked at the pictures and text but I obviously still have questions.

Thanks

Disc Brake Distribution Block

Cuda Dis Block.jpgCuda rear hold off.jpgCuda 3 port hold off.jpg

1972 Cuda 340 4 speed, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto, 1965 Satellite 4 speed
Re: 1970 Cuda brake questions [Re: cdstl] #3001168
01/02/22 03:51 PM
01/02/22 03:51 PM
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cdstl Offline OP
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From the FSM...

Cuda Dis block 1.png

1972 Cuda 340 4 speed, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto, 1965 Satellite 4 speed
Re: 1970 Cuda brake questions [Re: cdstl] #3001186
01/02/22 04:21 PM
01/02/22 04:21 PM
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DoctorDiff Offline
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The metering (hold-off) valve delays FRONT braking in low traction situations.
The proportioning valve delays REAR braking.
I prefer a combination valve (one piece distribution block/proportioning valve) as it incorporates fewer fittings which may leak.
I don't see the need for a metering valve in most of our applications, as few muscle cars are driven on snow and ice.

Re: 1970 Cuda brake questions [Re: cdstl] #3001191
01/02/22 04:27 PM
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The hold off valve restricts pressure to the FRONT disc brakes until the rear drum brakes develop enough pressure. This allows the shoes and pads to apply simultaneously. This function is not needed in an all drum, or all disc, system. It is solely used in a disc/drum combo.

The proportioning valve decreases the rate of pressure rise to the rear brakes once the hinge point is reached. This is due to the nature of self energizing drums applying additional leveraged braking force as they "dig in". Without this function the rears would tend to lock up. The hinge point will vary according to rear drum size, essentially, and the FSM sometimes lists that number. If you happen to have non-self energizing rear drums, like on my 51, you do not want this. Nor do you want this for rear discs, if they lock the rears you miscalculated the rear caliper sizing.

Re: 1970 Cuda brake questions [Re: cdstl] #3001199
01/02/22 04:43 PM
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cdstl Offline OP
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Thanks for the input guys, that was in record time. It's Sunday I guess.

It's a disc/drum car.

So it sounds like I can delete the metering valve and just use the distribution block and proportioning valve. Cass, do you have a recommendation for a combination distribution/proportioning valve?

Thanks again.


1972 Cuda 340 4 speed, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto, 1965 Satellite 4 speed
Re: 1970 Cuda brake questions [Re: cdstl] #3001201
01/02/22 04:50 PM
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DoctorDiff Offline
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My 1 piece prop valve will be back in stock tomorrow.
It simply bolts in place of a drum brake distribution block. See below:
https://www.doctordiff.com/1-piece-proportioning-valve.html

Re: 1970 Cuda brake questions [Re: cdstl] #3001202
01/02/22 04:56 PM
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Originally Posted by cdstl


So it sounds like I can delete the metering valve


I would not do that. It is also designed to prevent front brake lock up under light braking and slippery conditions. Sand, gravel, rain, ice, snow, oil, etc. Though the book specifically says icy any of those conditions can apply.

Re: 1970 Cuda brake questions [Re: cdstl] #3001203
01/02/22 04:58 PM
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cdstl Offline OP
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I actually found this from a place called Carolina Classic trucks. They offer it as a replacement for the '73 Prop valve which is not reproduced.

https://www.carolinaclassictrucks.com/73-cuda-prop-valve.html

PV4_560x560.jpgproportion-valve-pv2-1.jpg

1972 Cuda 340 4 speed, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto, 1965 Satellite 4 speed
Re: 1970 Cuda brake questions [Re: cdstl] #3001245
01/02/22 06:20 PM
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Originally Posted by cdstl
I actually found this from a place called Carolina Classic trucks. They offer it as a replacement for the '73 Prop valve which is not reproduced.

https://www.carolinaclassictrucks.com/73-cuda-prop-valve.html



Side note: I learned last year when using a prop valve with a safety mechanism (as pictured above), it's important to remove the brake warning light "switch" and replace it with special thread-in tool that holds the valve in place so that while bleeding the brakes the safety mechanism doesn't trigger when it "senses" a lack of pressure during bleeding. These safety mechanisms are nearly impossible to reset without taking the prop valve apart.

Do your research to reduce frustration.

Last edited by BigDaddy440; 01/03/22 03:58 AM.

1969 A12 Roadrunner
1970 Plymouth Cuda
1968 Dodge Dart
Re: 1970 Cuda brake questions [Re: BigDaddy440] #3001294
01/02/22 08:29 PM
01/02/22 08:29 PM
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trw1982 Offline
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bigdaddy440: where to get such a tool please? tia

Re: 1970 Cuda brake questions [Re: BigDaddy440] #3001300
01/02/22 08:55 PM
01/02/22 08:55 PM
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cdstl Offline OP
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Thanks for the advise


1972 Cuda 340 4 speed, 2001 Ram CTD 4x4 6 speed, 1970 Duster 408 4 speed, 2001 Ram 5.2 4x4 auto, 1996 Ram 5.9 2x4 auto, 1965 Satellite 4 speed
Re: 1970 Cuda brake questions [Re: trw1982] #3001338
01/02/22 10:55 PM
01/02/22 10:55 PM
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BigDaddy440 Offline
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Originally Posted by trw1982
bigdaddy440: where to get such a tool please? tia


[Linked Image]


1969 A12 Roadrunner
1970 Plymouth Cuda
1968 Dodge Dart
Re: 1970 Cuda brake questions [Re: BigDaddy440] #3001398
01/03/22 10:27 AM
01/03/22 10:27 AM
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The 70-72 B and E used the Kelsy Hayes single piston front calipers with the 10.98" rotors. For 70 Early system was 3 part, and later they moved to 2 part system, but it had the 3 basic parts. Follow on years moved to a single combined valve with all 3 in one.

1. The distribution block and safety warning. 2. As stated the metering block used with KH system delay the front brake application to allow the drums to start working. 3.The proportioning valve for the rear drum is not a delay, but at a set pressure reduces the pressure to the rear drum by 50% primarily because the drums are self applying once they grip. Higher pressure required for the disc, that is not needed on the rear drum.

The system is designed to prevent the front brakes from over applying is a poor traction situation such as rain, snow and preventing a loss of control of the rear end, spin".
The older bendix for the B body had a proportioning valve but did not need a metering valve for that system.
The Chrysler training video have a good explanation how the whole system works.







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