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Author Topic: Master cylinder for 4 wheel power disc brakes?  (Read 1482 times)

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Offline sponge003

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Master cylinder for 4 wheel power disc brakes?
« on: January 17, 2016, 05:19:09 PM »
Need some help!!

We have a 79 Pinto that we road race in Lemons endurance races.

It has 10" front discs with GM metric calipers and a 88 T bird super coupe rear axle(8.8) with the T bird stock rear Disc brakes . We have been running with a manual stock pinto master cylinder and no proportioning valve. It works but we have to use a lot of pedal pressure and its almost impossible to lock up the brakes. also it looks like the rear brakes are hardly used at all.

So we decided to upgrade to a stock 79 Pinto power booster and master cylinder to get some more brake pressure and take some physical stress off the driver as we drive long stints in the car (2 hours).

installed the master and booster, had to modify the length of the booster rod but got everything installed and after we bled the system it holds a good pedal without the engine running.

but when we fire up the engine it seems like the pedal has a LOT of travel and almost goes to the floor before getting semi solid. We have not been able to test drive yet

anyone have any ideas?

Is there a better choice for a MC? I am going to look at a Tbird super coupe master as it is made to operate 4 wheel disc and I might be able to get it to fit on the pinto booster?

Appreciate the responses

Offline pinto_one

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #1 on: January 18, 2016, 06:30:31 AM »
Sounds like you have air in the lines someplace ,since you changed the other parts you may have made it hard to bleed the air out of the system , next the flexible line may be old or too long , they will also make pedal travel longer , you might have to get some Teflon lined brake lines , they help a lot ,

76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

Offline sponge003

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #2 on: January 18, 2016, 11:26:52 AM »
We thought we had air but have bled to snot out of the system to no avail./

Offline dick1172762

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #3 on: January 18, 2016, 02:01:39 PM »
Sounds like you have a wrong length rod in the booster or the rod hooks on to the brake petal arm at the wrong place. The brake pedal has to be one from a power brake car. You don't state what car the booster came out of. Better way would have been a smaller diameter piston master cylinder. Example would be a drop from 1" to 15/16".
Its better to be a has-been, than a never was.

Offline sponge003

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #4 on: January 18, 2016, 02:10:26 PM »
Booster is brand new  a 79 pinto

Offline pinto_one

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #5 on: January 18, 2016, 08:09:39 PM »
Dick is right on the pedals , they are in a different place , or height from the long bolt that holds the brake pedal, and the adjustment of the pin into the master cylinder from the booster could be off , everything adds up , and can go wrong and end up like an old chev when the brakes get wet , you hit them and it goes FASTER 😸

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Offline sponge003

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #6 on: January 20, 2016, 08:13:40 AM »
Ok next question is who has a pedal assembly for sale for power brakes?

Offline Pinturbo75

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Re: Master cylinder for 4 wheel power disc brakes?
« Reply #7 on: April 21, 2017, 08:47:19 PM »
what engine is in the car
75 turbo pinto trunk, megasquirt2, 133lb injectors, bv head, precision 6265 turbo, 3" exhaust,bobs log, 8.8, t5,, subframe connectors, 65 mm tb, frontmount ic, traction bars, 255 lph walbro,
73 turbo pinto panel wagon, ms1, 85 lb inj, fmic, holset hy35, 3" exhaust, msd, bov,