Bought a power break setup off of ebay-it has a long gold bracket that bolts onto the frame where the original 3bolt master cylinder bolted on-it has a 7inch booster and I believe, what they refer to as the "corvette master cylinder"-my husband thinks it looks a lot like the master cylinder on his 68 impala ss427.
Question: since we're staying with 4wheel drum breaks, do we need a proportioning valve? If so, would it go in the front or rear line? Also, when adding a 2circuit master cylinder, which circuit does which breaks-does the front do the front breaks and the rear the rear breaks or visa versa?

Thanks again!

-Jazz and Don

 

I am fairly certain that the corvette and impalas had a very similar master cyl design. GM used the cast iron MC with the spring clip tops for quite some time. If you are staying Drum/Drum on the truck you shouldnt need a proportioning valve but if you are considering doing front discs later down the road then you will benefit by installing it now. you can get a really cool setup from many companies that have a brake distribution block and prop valve combo for about 100 bucks. If you decide to install the prop valve for the option of an easy front disc upgrade down the road you can adjust the valve at center which will yield a 50/50% distribution. you can fine-tune your brakes if you want the truck to have more or less front/rear braking power.

As for the port circuits on the MC, usually the port closest to tthe firewall/booster etc is the front circuit and the forward part of the MC (furthest from the booster) is the rear circuit.