Master cylinder differences

Reply Subscribe

Thread Tools

Search this Thread

Aug 8, 2011 | 09:40 AM

PA74F250

Thread Starter

Cargo Master

Joined: Jul 2010

Posts: 2,099

Likes: 8

From: York, Pa

Master cylinder differences

I was wondering if anyone knew any difference between the the one that I have yet that was for the power drum brakes and power disc? I switched to the HP D60 from the 79 F350 and also added the prop valve from the same truck. Everything works but it just doesnt seem to have the stopping power it should. All brake hardware is brand new nothing reused except the prop valve. I was wondering if I should be using the later style master cylinder? The way it is now it wont even lock the hummer tires up. My dads 78 F250 would lock the tires up with 38's so I'm confused. Right now I would say the drum brakes worked just as good if not better.

Aug 9, 2011 | 09:18 AM

Joseph69

Senior User

Joined: May 2010

Posts: 246

Likes: 1

You need a Disc Brake MC, in fact you can look for a F350 MC with a dual diaphragm booster. The Disc Caliper uses more volume to apply pressure, the wheel cylinder uses very little. Get an 1979 F350 MC and Booster and you will be very happy, you will need some adapters for the larger line size, but running larger lines (I think 5/16 instead of 1/4, cant remember) will give you some more braking, instead of just adapters on the MC. Do some searching, there are a lot of write ups.

Aug 9, 2011 | 09:27 AM

PA74F250

Thread Starter

Cargo Master

Joined: Jul 2010

Posts: 2,099

Likes: 8

From: York, Pa

I will have to order a MC soon. I did take the brake lines and everything off the 79 F350 and they did fit right in my MC? So I'm not sure if they are really any larger. Do you think I can just use the booster I have? I'm not sure what may be different inside them but the one I have is large it all but touches the valve cover.

Aug 9, 2011 | 10:33 AM

Joseph69

Senior User

Joined: May 2010

Posts: 246

Likes: 1

Either Booster should work.
This is the Dual Diaphragm it is smaller in diameter.

This one should be like the one you have, single diaphragm and bigger, closer to the valve cover.

They both should have the same bolt pattern for the MC

Aug 9, 2011 | 10:40 AM

PA74F250

Thread Starter

Cargo Master

Joined: Jul 2010

Posts: 2,099

Likes: 8

From: York, Pa

You are exactly right with the pictures. I think I know where I can pick up a used booster off another 79 F350....I hope. Since I had power drum brakes do you think the brake rod in the new booster will connect to my pedal? I was doing some searching and some say the brake pedals are different? I didn't know that. I can see this is going to get interesting inside the cab.

Aug 9, 2011 | 10:49 AM

PA74F250

Thread Starter

Cargo Master

Joined: Jul 2010

Posts: 2,099

Likes: 8

From: York, Pa

Oh yea another question...Do you think the bolt pattern for the booster itself going through the firewall is the same?

Aug 9, 2011 | 10:58 AM

Joseph69

Senior User

Joined: May 2010

Posts: 246

Likes: 1

They should be, the only differences in the different setups is the length of the plunger rod going into the MC. You may have to grind it down to fit, but everything else should fit. You will know immediately if the length is wrong.