Upgrade master cylinder with a disc brake conversion?

boltbrain

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When doing a conversion to disc brakes is it a good idea to go to a later model master cylinder/booster that served four disc brakes? I’ve been watching some YouTube videos on the swap and only heard one comment on it, he changed out his old master/booster for a later model one. I thought I heard him say for an eight. Maybe an 08. My old m/c and booster need replacing anyway, just don’t know what to get. Thanks
 

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A larger booster makes sense, but I would just use one from HD brakes on a squarebody of the same year. You also need to change the proportioning valve to one for front disks. The disk brakes stop better overall, but require higher pressure than drums.
 

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Sounds good, thanks!
 

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A larger booster makes sense, but I would just use one from HD brakes on a squarebody of the same year. You also need to change the proportioning valve to one for front disks. The disk brakes stop better overall, but require higher pressure than drums.
Any idea where I can get the right proportioning valve?
 

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I just found out I’ve got 13” discs on the front ( Dana 44). and 11” drums on the rear, so if I put discs on the rear I can go to 13”, same parts as up front. I doubt it’s easy to find 13” back plates, ( to keep it drum) but might start looking.
 

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I used a master cylinder from a ‘99 C3500, it is a disc/disc vacuum booster application. It bolted right on to the stock booster on my 91 Blazer.
 

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There are disk brake conversion kits, so I assume they sell a proportioning valve to go with them. There are also hot rod adjustable prop valves from Summit, Jegs and other sources. You just install and adjust it until you like the front/rear bias.
 

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T
I used a master cylinder from a ‘99 C3500, it is a disc/disc vacuum booster application. It bolted right on to the stock booster on my 91 Blazer.
Rhanks, I’ll see if the 91 works on a 79, ask the parts guy
 

boltbrain

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There are disk brake conversion kits, so I assume they sell a proportioning valve to go with them. There are also hot rod adjustable prop valves from Summit, Jegs and other sources. You just install and adjust it until you like the front/rear bias.
Thanks, parts guy told me most replacements aren’t available and like you said they get swapped out for adjustable, mostly. There are lots of good options, Lugnut has the disc/ disc, so does Wilwood and Inlinetubing, others. They all work for all disc/disc apps
 

boltbrain

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Thanks, parts guy told me most replacements aren’t available and like you said they get swapped out for adjustable, mostly. There are lots of good options, Lugnut has the disc/ disc, so does Wilwood and Inlinetubing, others. They all work for all disc/disc apps
I meant all the disc/disc ones work for any disc/disc vehicle, or so it seems anyway.
 

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I just bought a Disc/Disc proportioning valve from Southwest Performance parts 42.99 free shipping.
 

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Thanks, I got the valve LugNut had with the conversion kit I got from them. It only works one line, the rear. I decided I wanted it up by the master cylinder, where the ABS module would be if I had abs. So I ran new lines, which was a challenge as I had to perfect my double flaring. But I like the rear line going straight back from the master, instead of under the radiator cowl to the passenger side. The T fitting on the rear diff was easy to move to the left. Welded little brackets in for the rear hoses. Can’t say how the valve works yet as I haven’t finished bleeding
 

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