Looking at various replacement Master Cylinders for my 87 Camaro, 305TPI, Front and Rear Disc brakes. Nearly everyone I have looked at list having the primary port size of M11-1.5 Bubble Flare and the secondary port as M12-1.0 Bubble Flare. Somewhere I read that the line size from the master cylinder to the proportioning valve should be 1/4". I can find the M12-1 tube nuts for 1/4 line but I can not find the M11-1.5 for 1/4 line. I can find it for 3/16" line. I have looked all over(AGS, auto parts stores, BrakeQuip, Dorman, SUR+R, FMSI, to name a few) without any luck. Am I correct in remembering the lines should be 1/4" or am I mistaken based on I can not find the M11-1.5 for 1/4 line. Thinking about just getting a M11-1.5 for 3/16" line and drilling it out to 1/4", or is that a bad idea?

Any thoughts on this would be awesome.

 

I should have stated that I swapped the rear end from drum to disc brakes. I sold the drum brake rear end, along with the master cylinder and proportioning valve because I thought I would not need them.

 

It should be IMPOSSIBLE to find bubble flare nuts for Imperial tubing sizes. Not sure where why or how you're finding such a thing. Not saying you're not; only, that's about like finding a 10mm bolt with a 5/8" head. Mismatch.

Metric lines come in metric sizes. Their tubing sizes are not Imperial. 6mm is the size closest to ¼". I recall putting a 91 or so rear axle in my 83 car. One of the minor details involved was hooking up the rear's rubber hose, with its 2 bubble flare connections to the calipers and 1 bubble flare to the car's line, to my lines, which were ¼" w SAE flares. The solution I found was to get a short piece of 6mm line w bubble flare on it, flare it to ¼" SAE on the other end, and assemble with a flare union. It took MANY tries before I was finally able to get my SAE flare tool to grab hold of the 6mm line tight enough to complete the flaring process.

¼" = 6.35mm; the common metric size near that is of course 6mm

3/16" = 4.7625mm; tubing size closest to that would be 5mm, not 3/16"

Try looking for the right thing. You may get better results. The Imperial measurements you have from "somewhere" are obviously for 83-back cars, since 85-up were metric (84 was a mixture as they changed over). Your 87 is metric.

 

M11-1.5 or M12-1.0 is the tube nut thread type. The inner diameter of the tube nut might be sized for metric or inch tubing.

The stock line sizes on your car are 3/16" tubing front, and 6 mm tubing rear. The stock tube nuts on rear line truly are sized for 6 mm tubing and will not fit on 1/4" tubing without drilling out the ID a bit.

However, most aftermarket tubing sold in the US is inch size, and most the aftermarket tube nuts also are sized for inch tubing. That M11-1.5 or M12-1.0 tube nut you buy from Summit Racing likely has an ID sized for 1/4" tubing. And you can form acceptable bubble flares on 1/4" tubing using a metric bubble flaring tool.

 

Thanks for all the information.

Part of my issue is that I am replacing the old steel (rusted through) lines with stainless steel lines (pre-bent, supposed to be O.E.M. replacements). The stainless steel lines came with metric fittings at the ends, which is not a problem. Swapping to the disc brake rear end, I had to change the proportioning valve. I bought one from POL Performance for 4 wheel disc. The proportioning valve came with imperial threaded ports - inlet 1/2-20 inverted, 7/16-24 inverted, outlet for rear is 9/16-18 inverted and the two for the front are 3/8-24 inverted. The front lines I bought match up to the proportioning valve, the rear does not, but I plan on replacing that fitting if I have to. Unless I dole out 399.99 plus shipping for a correct N.O.S. GM proportioning valve. I plan on using the POL Performance proportioning valve. Finding usable parts for our 3rd generation F bodies in this area is nearly impossible. I searched junk / scrap yards in a 200 mile radius and no one had a disc/disc proportioning valve that fits my car, lots of disc/drum ones. AC Delco and all the after market master cylinders for front disc and rear disc have M11-1.5 Bubble flare and M12-1.0 bubble flare ports. I plan on making my own lines from the master cylinder to the proportioning valve, once I find the correct fittings. I can find just about everything except for the M11-1.5 for 1/4 line (plan on using 1/4 stainless steel for these).

 

Where did you find NOS prop valves? I'm interested in that.

 

I used my parts manual, looked up the part number and did a google search. If I remember right, because I was looking all over the place it was on eBay. Hawks Motorsports has a reconditioned disc/disc for 300. Still a little out of my price range.