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SN95 brake help

 
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89Gmcsierra
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Joined: 28 Oct 2012
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Location: Hazleton, Iowa
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PostPosted: Sun Mar 23, 2014 7:36 pm    Post subject: SN95 brake help Reply with quote

1980 mercury capri brakes and axle upgrade.
i bought a 86 mark 7 rear axle with rear disc i know 1.25" longer axles rims i have work but i know with rear disc i have to upgrade booster and master cylinder was going to go to SN95 front brakes and booster/master cylinder but not sure on prop valve and 3-2 kit. any help would be helpful.
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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Sun Mar 23, 2014 9:37 pm    Post subject: Re: SN95 brake help Reply with quote

89Gmcsierra wrote:
1980 mercury capri brakes and axle upgrade.
i bought a 86 mark 7 rear axle with rear disc i know 1.25" longer axles rims i have work but i know with rear disc i have to upgrade booster and master cylinder was going to go to SN95 front brakes and booster/master cylinder but not sure on prop valve and 3-2 kit. any help would be helpful.



Can't understand the question.... BUT you do not want the residual valve for the rear/drum brakes.
I don't know why you call the safety valve a prop valve. All it does is turn the brake light on and stop the fluid from going there.
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clay
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1972 Chevrolet Nova

PostPosted: Sun Mar 23, 2014 10:19 pm    Post subject: Reply with quote

You don't really need to do anything to your master if you don't want to. As af2 mentioned you will have to lose the residual pressure valve when you swap from drums to disc. On my Nova it was located in the master cylinder behind the inverted flare fitting that was pressed in. I ran a tap in existing center hole, put a screw in and pulled the fitting with a slide hammer. The drum master works great, only differences after the residual valve removal is it has a smaller bore diameter than the disc master and the front and rear resevoirs are the same size instead of being larger for the front discs. I took what is called the pro portioning valve apart and saw what af2 said - all it does is basically turn the brake light on when there is a pressure loss in one of the systems. Now most of what I know is gm related so you'll have to do some research on the Ford end of things. Clay
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89Gmcsierra
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PostPosted: Sun Mar 23, 2014 11:12 pm    Post subject: Reply with quote

i read something to do with these parts
http://www.jegs.com/i/Wilwood/950/260-11179/10002/-1
http://www.latemodelrestoration.com/item/M2450A/Mustang-Brake-Proportioning-Valve-Plug
but i've never screwed with updating brakes. so i'd like to know if its really what i need not something that people just saying i need when i dont. I have kinda low budget and clocks ticking may 3rd first race for this year for me.
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clay
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1972 Chevrolet Nova

PostPosted: Sun Mar 23, 2014 11:34 pm    Post subject: Reply with quote

With enough research you should be able to use all factory parts. Sounds like you are in a time crunch though. When we took everything off of a car and put it on a truck I did use a proportioning valve similar to what you listed because of the drastically different weight distribution. You shouldn't need to do that. Put the brakes on, remove any residual pressure valves, bleed the brakes and try them out. Goes without saying go easy. It won't be that you can't stop - it should do that fine on an easy stop. Go to a back road, and at about 20 or so stand on the brakes and see what happens. I think the front should lock first as it's easier to deal with a push than losing the rear. If the rear locks first then you need an adjustable proportioning valve. Clay
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Mon Mar 24, 2014 9:47 am    Post subject: Reply with quote

The prop valve is also called a brake metering hold off valve. For each brake type it is quite different. For disc brakes it is 2 psi and for drum it is 10psi. So using the drum on a disc setup would cause the discs to drag and heat up trashing them. There is a bias switch that will turn the brake light in the event of pressure loss in either front or rear systems like Adam was referring to.

Now you can buy a pressure metering valve (bias valve) to adjust the pressure delivered to one of the systems. Usually the one that is locking up too early would it so that you can adjust the bias front to rear or rear to front depending on what the car needs. The factory usually does a good job at this so if you keep all the factory hardware you should be fine.

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Last edited by Paul P on Mon Mar 24, 2014 6:32 pm; edited 1 time in total
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SMOKEmUP
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PostPosted: Mon Mar 24, 2014 11:33 am    Post subject: Reply with quote

Can you use (get) the proportioning valve off of the Mark 7?
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89Gmcsierra
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PostPosted: Tue Mar 25, 2014 6:33 pm    Post subject: Reply with quote

sounds like i have to have adjustable. front brakes are 10.84" and rear are 11.35" so im sure the rear would lock way before the front.
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af2
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1933 Willys Coupe

PostPosted: Tue Mar 25, 2014 7:00 pm    Post subject: Reply with quote

89Gmcsierra wrote:
sounds like i have to have adjustable. front brakes are 10.84" and rear are 11.35" so im sure the rear would lock way before the front.


It all depends on the caliper puck size not the rotor size. I would bet the calipers are close to the same size.
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