1982 Master Cylinder Plumbing

[jayd_68]

I'm converting a 1968 C10 to Disc and 5 lug using 1982 C10 parts, got a proportioning valve on order for GM Disc/Drum. The donor truck was missing the master cylinder/proportioning valve and I don't know which port is front or rear.

Chevy's I've owned the front port was front axle and the port next to the firewall was rear axle. The 1982 is a step style master and the fittings are the same as the 1968 master, 9/16-18 and 1/2-20 but the positions are swapped and I can only assume the rear port is for the Front axle.

Does anyone know which port is front and rear?

 

[Georgeb]

Are
The resivoirs the same size?

 

[jayd_68]

It has a plastic reservoir thats irregulary shaped due to the stepped bore, you would have to fill each side and measure the difference if any.

They just listed another 1982 C10 at the local u-pull salvage, I'll check it tomorrow to see if the brake system is intact.

 

[Keith Seymore]

It has a plastic reservoir thats irregulary shaped due to the stepped bore, you would have to fill each side and measure the difference if any.

They just listed another 1982 C10 at the local u-pull salvage, I'll check it tomorrow to see if the brake system is intact.

The port adjacent to the large portion of the reservoir is for the front disks; the smaller reservoir is for the drums.

If yours is like mine then front goes to the front; rear goes to the rear.

K

 

[jayd_68]

The one in the salvage is the opposite of yours, the rear port goes to the front and the front port goes to the rear. I checked a couple of other GM's with the same master and they all were plumbed the same way.

 

[Keith Seymore]

The one in the salvage is the opposite of yours, the rear port goes to the front and the front port goes to the rear. I checked a couple of other GM's with the same master and they all were plumbed the same way.

The port adjacent to the large portion of the reservoir is for the front disks; the smaller reservoir is for the drums.

Nonetheless, this is still true no matter what.

The disks need the added volume to replenish the fluid due to wear, because of the size of the pistons (compared to the size of a wheel cylinder).

Port placement can be dictated by underhood clearance (moving the smaller reservoir to the front helps clear a highly sloping hood, like Astro/Safari van) or by features in the master cylinder, like quick take up or lack thereof.

K