Proportioning Valve Outlet Fitting

[Father&son56project]

A possibly dumb question here, but here it goes: I’m putting in a disc/disc brake system and I need to know which fitting to use at the outlet (to the rear brakes) of the PV4 universal GM style proportioning valve. I plan to run 3/16 line out to the rear. The product info from MBM Brakes for the valve tells me that the outlet is a 9/16-18 fitting, but says nothing about line size. I can order a “9/16-18 Inverted Flare Nut; Line Size: 3/16" like this from Rockauto:

https://www.rockauto.com/en/moreinfo...1000606&jsn=67

Or I can get the “Proportioning Valve Adapter Fitting Kit - Set of 3” from CPP like this:

https://classicperform.com/cp2091

Are the fittings from both places in fact the exact same thing (other than getting 2 unneeded ones in the kit)? Sorry if this sounds dumb, but all my searching has turned up conflicting info and I have zero knowledge where fittings are concerned. Any input would be greatly appreciated.

[Willie Makeit]

search for 9/16-18 (thread size) and then sort by tube size. Tube nuts are made in various configuration.

The link to rock auto seems to be the one you want.

[Father&son56project]

Thanks Willie Makeit! I (erroneously) assumed that the outlet port in the proportioning valve was meant for a specific line size. This frees me up to get one of those inexpensive 9/16-18 fittings and hopefully start making some progress in the shop.

[cadillac_al]

Why 3/16"? Most trucks use 1/4" to the rear drums. discs might need even more fluid.

[Father&son56project]

Al, I did a ton of searching online, and the info was all over the map regarding 3/16 vs 1/4 rear line sizes. In the end I picked 3/16 as I will be running an Explorer disc rear end. The engineers at Ford picked 3/16 line for the entire rear system, so I figured I'd go with what they picked.

[chevyguyase]

I agree with cadilac al, I use 1/4 inch from the master cylinder to the prop valve and from the prop valve to the t fitting at the rear differential and from the t fitting to the rear wheel cylinders I use 3/16. That 1/4 inch line to rear feeds two rear wheel cylinders.

[Willie Makeit]

3/16" is fine for disc systems

[cadillac_al]

I guess I would have to agree if ford uses 3/16 in their rear disc systems. I have never seen it in any vehicle that I have owned though.

[theastronaut]

Line size doesn't really matter, 3/16 isn't small enough to be restrictive. Newer trucks have 3/16 all around, even with rear drums.