OEM Brake line/fitting sizes

[guy0783]

So I've been working on the truck it's a 63 3/4T K20. It got some new pushrods, a rear pinion seal, plugs, wires, hoses, fresh fluids, etc...

After replacing the brake master cylinder, I have a seeping leak where the line connects to the master. I just discovered it at lunch as I made a point to check and recheck it. I figure I might as well replace the line, but can't find the line size or fitting sizes. I've seen some threads on brake line, but am mostly seeing disk brake conversion info.

Anyone know the OEM sizes?

[guy0783]

I think it's a 1/4 line and the fittings have standard threads. Would the info be in my 1963 truck manual to verify when I get home? Or is my best bet to pull the line and take it to the parts store to match up?

[rvrfoot]

I think mine was 3/8 or 5/16

[Captainfab]

Stock drum/drum brake line size is 1/4".

[guy0783]

Thanks guys, I'm gonna tackle it this afternoon and hopefully get it taken care of. I appreciate the help.

[guy0783]

Got home today, pulled the brake line off, and there were no cracks or deformation of the flare that I could see. I think what happened was that I attached the brake line to the master before tightening the master to the firewall and when I cinched that down it pulled on the line so it wasn't square.

Anyway, I gently bent the line so that it fit the master without any sideways tension and it sealed up. Bled the brakes, drove around doing some hard braking and it appears to be taken care of.

Thanks for the info though, I appreciate it!

[ChiefRocka]

Originally Posted by rvrfoot

i think mine was 3/8 or 5/16

wow !

[guy0783]

Leak showed back up today so I decided to pull it and replace. Even after a PB Blaster soak, the lower flare fitting was seized and I rounded off a couple corners. I decided to just cut the line just above the fitting and use a socket to get it out. That worked pretty easy.

Went to O'Reilly's and matched it up. The one I picked out is 1/4in x 30" with 7/16 standard thread flare fittings. It was a little long so I had to put an extra bend in there, but it fit up nicely.

It appears 1/4in brake line with a 7/16 standard thread fitting on each end is correct for line from master to junction on a 63 3/4T 4x4.

[guy0783]

Here's a pic.

[rvrfoot]

You nailed it.