Who's master cylinder and booster?

[BugzC10]

Do you know what vehicle this master and booster possibly came out of? Previous, previous owner installed it. The booster is approx 8-9" wide. And as you can see the booster is mounted directly to the fire wall. My brake pedal is also different. The slanted master and the truck lower in the front is a PIA when bleeding the brakes.

[BugzC10]

Nobody?

[kda2000]

This looks like the brake booster and MC that is in my '86 Fireo -- its definitely a mid-80s GM setup, out of a midsized or compact. - Ken

[RichardJ]

I am using the same booster. It's from a late '70s or early '80s Chevy van. I wanted the booster against the firewall, because I don't like the MC hanging out almost to the front of the engine. I used the complete disc brake setup from a '76 3/4 T so I used that MC as well.

Your signature says "73-87 front suspension w/Disc". The '76 had a brake, Combination Valve mounted on the crossmember under the radiator. If you don't have the Combination valve, did they include a stand-alone proportioning valve on the rear brake line? I can see a distribution block/brake light switch in your pictures.

Your signature also says, " ??? Cam". Unless you have really weak manifold vacuum, I'd loose that huge vacuum reservoir canister.

[BugzC10]

Originally Posted by RichardJ

I am using the same booster. It's from a late '70s or early '80s Chevy van. I wanted the booster against the firewall, because I don't like the MC hanging out almost to the front of the engine. I used the complete disc brake setup from a '76 3/4 T so I used that MC as well.

Your signature says "73-87 front suspension w/Disc". The '76 had a brake, Combination Valve mounted on the crossmember under the radiator. If you don't have the Combination valve, did they include a stand-alone proportioning valve on the rear brake line? I can see a distribution block/brake light switch in your pictures.

Your signature also says, " ??? Cam". Unless you have really weak manifold vacuum, I'd loose that huge vacuum reservoir canister.

I'm just learning exactly what front suspension and MC I have. That's what prompted this thread. When I got the truck I learned that the front end was from a later model. It may not be the complete front suspension, but pieces such as the lower and upper control arms and disc. I just became aware of the proportioning valve for the 73-87 was located on the front crossmember. Since mine is located below the MC it made me wonder how much of the front suspension is stock to 1970 and how much of it is 73-87. My soft brake line attachment is located to the rear of the upper control arm. I think that's we're the 1970 hard line ends. 1971 & 1972 hard line ends in front of the UPC. The 73-87 hard line come through the frame. I need to buy shorter soft lines.
I like the brake booster with out the braket....doesn't stick out as far, but not crazy about the MC slant nose.
As far as the brake booster auxiliary vacuum tank. I didn't like the feel of the brake pedal..low vacuum driven by the ???cam, so I added it. Seems to have helped, better feel.
Thanks for your input on the MC & Booster

[steelhorse]

Looks like one from an Astro van.

[RichardJ]

>>proportioning valve for the 73-87 was located on the front crossmember. Since mine is located below the MC <<

If you are referring to the item visible in your first picture, that isn't a proportioning valve. It isn't any kind of valve. It's a switch. That's all it is. It is there to turn ON the dash brake light indicator. If there is a hydraulic brake failure in either the front or rear brake system, that switch will turn ON the dash indicator light, if you have one. That same indicator lamp would be used for youe E-brake light.

Without a proportioning valve in the system, you should be able to lock-up the rear brakes with ease. On a wet road, you should have a hard time keeping from locking up the rears. If you don't have that problem, your front disc brakes are not working properly.


>> proportioning valve for the 73-87 was located on the front crossmember.<<

That isn't just a proportioning valve. It has the brake light switch, plus a metering valve for the front disc brakes, plus a proportioning valve for the rear drum brakes. It is called a Combination Valve because it combines all three of those functions into one unit.

[BugzC10]

Originally Posted by RichardJ

>>proportioning valve for the 73-87 was located on the front crossmember. Since mine is located below the MC <<

If you are referring to the item visible in your first picture, that isn't a proportioning valve. It isn't any kind of valve. It's a switch. That's all it is. It is there to turn ON the dash brake light indicator. If there is a hydraulic brake failure in either the front or rear brake system, that switch will turn ON the dash indicator light, if you have one. That same indicator lamp would be used for youe E-brake light.

Without a proportioning valve in the system, you should be able to lock-up the rear brakes with ease. On a wet road, you should have a hard time keeping from locking up the rears. If you don't have that problem, your front disc brakes are not working properly.


>> proportioning valve for the 73-87 was located on the front crossmember.<<

That isn't just a proportioning valve. It has the brake light switch, plus a metering valve for the front disc brakes, plus a proportioning valve for the rear drum brakes. It is called a Combination Valve because it combines all three of those functions into one unit.

That is a proportioning valve below the master cylinder like these pictures. It's just mounted with the switch pointing downward. My brakes work perfect.

[RichardJ]

This is what I see in your first picture. It is a pressure differential switch. A switch and nothing more. It is not a proportioning valve and it is not a brass combination valve that you are showing in your last post.
If you have a proportion valve, it may be somewhere in the line to the rear brakes.

[BugzC10]

Originally Posted by RichardJ

This is what I see in your first picture. It is a pressure differential switch. A switch and nothing more. It is not a proportioning valve and it is not a brass combination valve that you are showing in your last post.
If you have a proportion valve, it may be somewhere in the line to the rear brakes.

So IF it is as you say, what would the affect be when applying the brakes? My rear brakes don't lock up, nor do the front when mashing the brake peddle.
Note: I replaced the solid brake line that goes along the frame next to the engine back to the rear axle...no proportion valve found. I have not seen another inline valve. Are you saying that I'm getting equal pressure to the front and the rear brakes?
Sounds like when the previous owner installed the power brake booster and front disk setup he left the drum brake "differential" switch intact and neglected to install a disc/drum P valve.
I would put in a new Disc/Drum valve, but I'm considering converting the rear to disc and don't want to buy the valve twice. What P valve would you recomend for Disc/drum?