1968 GMC C20 Master Cylinder replacement question

[airkore65]

Looking to replace this eyesore in my engine bay with a Wilwood product. Would like to replace proportioning valve also. Currently running original drums.
Is this a simple swap? Wilwood tech is not replying to any contact. Bore size of the stock GM from my research on here runs from 1" to 1"1/8.
Any help would be greatly appreciated.

[Maximus]

I hope you actually find an answer to your question, I don't have any info to help you get your answer... but if it were me, I would vote for just refreshing the stock components (or replacing the MC with a rebuilt if your concerned about function/age). Willwood specializes in disc brake conversions, so their primary info is probably going to be for disc/drum and disc/disc setups, but you will need to find out if both of the necessary 10lb pressure valves will be in the body of the MC, or in the Prop Valve\Dist Block. Using stock components there is no question on if any necessary parts are missing...

A painted MC and prop valve/Dist block doesn't look too bad, and still able to swap out parts at a local parts store in the future if something fails....

[airkore65]

Thanks for the quick reply Maximus!
My concern with replacing with stock or rebuilt is the quality these days. I'm sure my original part was made with quality back in the day. Can't say that these days.

[tdangle]

I believe it's a 1 1/8 bore although it might be a 1" because of manual brakes. the proportioning valve you mention is really just a distribution valve as the front and rear get the same pressure in a 4 wheel drum setup. Personally I would just buy a new stock unit and paint it prior to install. Good Luck.