Brake line size on master cylinder?

[MNorby]

What size line/fittings are used on the master cylinder of a 72 3/4 ton 4x4 chevy truck? The smaller port firs a 5/16 line and the larger port looks like should fit a 3/8 but can't get it started. Tried a couple different lines and even tried an another MC. The factory line fits it fine and I could cut out that fitting so I can make my new lines but would rather be new. Is that a special size or something?

[cparman]

recheck this. Most all lines are 3/16 for the front, and 1/4 from rear.

[MNorby]

well, I guess i mean I need to know fitting size the threads into the MC itself. Was just gonna buy 12"ers so I can bench bleed the MC then make new lines since I eliminated the stock prop valve with a wilwood prop valve on the rear line and also am installing a 3/4 ton mc into a k5 so the front and rear lines are swapped. Going to make new line from MC to frame to clean it all up.

[cparman]

the line can be 1/4", but the fitting can be one of several different sizes. NAPA might have some of these, but I do not think so. When ever I buy a line kit from Master power Brakes, it will come with several different fittings to accept different thread sizes in the master cyl, or prop valve. NAPA will have some adapters that might take you from the standard line size fitting to where you want to go. Hope this helps

I am going out in the garage in a bit, and will shoot a pic or two of what I am talking about

[LONGHAIR]

since I eliminated the stock prop valve with a wilwood prop valve on the rear line

Can you elaborate on this a little?

[MNorby]

Originally Posted by LONGHAIR

Can you elaborate on this a little?

Just an adjustable prop valve on the rear line so I can adjust rear brakes so they don't lock before fronts. I'll take a picture when I get it all plumbed back in.

[MNorby]

Originally Posted by cparman

the line can be 1/4", but the fitting can be one of several different sizes. NAPA might have some of these, but I do not think so. When ever I buy a line kit from Master power Brakes, it will come with several different fittings to accept different thread sizes in the master cyl, or prop valve. NAPA will have some adapters that might take you from the standard line size fitting to where you want to go. Hope this helps

I am going out in the garage in a bit, and will shoot a pic or two of what I am talking about

Thats more what I was going after is fitting size so I can get an adapter or fitting for the end of some tube.

[Sinisterspeed]

I just delt with this myself. Napa did not have the actual fittings for the Master Cyl loose. I had to buy the 12" pieces of the GM Brakes lines that would fit the Master Cyl ports. They were only like 4 bucks each i had to cut the line and take the fittings from those short lines to install on the new lines I was bending. Cparman was right above with the 3/16 and 1/4 " line these are the size lines you will need to buy at Napa in order to get the fittings that will fit. I am sure someone sells them loose but thats how I had to find them.

[MNorby]

I ended up cutting and reusing the old fitting, wanted to make a bleeder hose and a new hose for the truck but have to use same fitting for both. Is that size metric or something???

[Sinisterspeed]

no I believe it's National Pipe with inverted flair.