Mustang Brake Master Pipe size


New Member
Apr 16, 2019
Grantham Lincolnshire uk
Hi I wonder if anyone can help, Im speaking from the United Kingdom, Ive been into American Cars for over 40 years, I have a chevy 3100 truck a 55 buick and a 41 Willys, The Buick has been fully restored but streetrod type 427 BB Chevy smoothed firewall Olds front clip to supply discs, Well the Master Cylinder Failed but its not Buick cos 55 Buicks never had power brakes. I narrowed it down to a 1982 Ford Mustang or cougar and ordered one from Rock Auto, It came and is the spitting image in all respects but the brake pipes are slightly smaller in size to the one that is fitted to my car. Thy are small and large in size front and back on my old master same on new but new is slightly larger hole front and slightly larger hole rear.....I take it one is metric the other Imperial, The question is can I put larger ends on my pipes? Anyone know?.
  • Sponsors(?)


Mod Dude
Feb 18, 2001
All pre 1987 Mustangs came with SAE fittings on the master cylinders. Unsure of the exact sizes though, but Ford varied the sizes of the ports based on the model to avoid installing the incorrect master cylinder on the wrong vehicle. LOTs of 80's fords used that same MC style, so while they look the same, the bores could be different. Do you know the bore size? Is it cast iron, or aluminum?

So yes, you can purchase new replacement nuts for the brake lines and reflare them to the new nuts, but i'd be more concerned with Identifying if the master is the correct one based on bore diameter. What made you think it was a 1982 Mustang master cylinder? As the 79-86 master is virtually the same physically