Hydraulic experts?

[Mathius]

Hi all,

I'm sourcing parts for a rear disc swap on my '76 Malibu. High Performance Pontiac just did an article on swapping '98-02 s-10 rear disks on almost any 10-bolt, 8.2", 8.5", or even 12-bolt GM's, from '64 'til now using s-10 parts.

My original quest was to use a setup from a '79 Seville, but I'm leaning towards the s-10 swap now.

Anyways... having said that, I picked up a dual master cylinder from a '79 trans am that was setup for disc/disc, and a power booster as well. I got a combination valve off of Ebay that's for a disc/disc setup. However, I don't know if I need to run residual valves or not?

The valve is from Gearheads. The literature for the gearheads combination valve says use a 10lb residual for drum brakes w/Underfloor Mount, which doesn't apply. The front brakes require a 2lb residual (For Front discs w/Underfloor mount). I'm not sure what an underfloor mount is? Is this the style of brakes where the pedal actually physically pushes a plunger in the brake booster?

I'm really confused as to whether or not I need a residual, and which one?

Also, is there any issue with using my existing hardlines in the rear? The article mentioned flex hoses, but I know some of the Cadillac setups had hard lines from the factory.

Mathius

[David Pozzi]

Underfloor mount is when the master cyl is under the floor. This was used in the fourties and fiftys cars. The master cyl is low and the residual valve helps keep the fluid from running back to the master cyl.

You don't need a residual valve at all if the master cyl is mounted higher than the calipers.
You don't really need a combination valve. an adjustable proportioning valve in the rear line is usually all you need.
There are reasons for the combo valve but it's main benefit on a disc/disc car are when driving on ice. I have a full explanation of that on my web page in the first gen suspension section.
You can use hardlines, but the calipers often have a hose from rear axle hard line to the caliper, the calipers move in relation to the housing since they are full floating calipers, they also have to be moved when changing pads. you need to have hoses on them.

Make sure you use front calipers with aprox the same diameter pistons as the S-10 system.

[Mathius]

Underfloor mount is when the master cyl is under the floor. This was used in the fourties and fiftys cars. The master cyl is low and the residual valve helps keep the fluid from running back to the master cyl.

You don't need a residual valve at all if the master cyl is mounted higher than the calipers.
You don't really need a combination valve. an adjustable proportioning valve in the rear line is usually all you need.
There are reasons for the combo valve but it's main benefit on a disc/disc car are when driving on ice. I have a full explanation of that on my web page in the first gen suspension section.
You can use hardlines, but the calipers often have a hose from rear axle hard line to the caliper, the calipers move in relation to the housing since they are full floating calipers, they also have to be moved when changing pads. you need to have hoses on them.

Make sure you use front calipers with aprox the same diameter pistons as the S-10 system.

Thanks David.