77 master cylinder
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
77 master cylinder
OK so I am a few steps into my brake rebuild and hydroboost install. I bought a master cylinder that was marked as a 77 power brakes just like all of the installs say. Question. How do you know if it is really a 77 cylinder. The casting number is the same as my 72. I keep reading about bore size being different but visually the only thing I can tell is that the very center of the new master cylinder piston is filled in while the very center of the old is hollow. I wish I could show a pic but murphy struck and my camera is dead. With my dial calipers the bore seems to be the same size. Just the hole in the center of the piston is different.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
But some of the suppliers are selling non-corvette masters and a mix of hodge podge parts.I've seen drum brake masters,masters with reversed line fittings,masters with adapters at the lines,same number masters with different pistons installed and on and on and on !!!
You can't rely on what the parts guy gives you as being correct.
I would go buy several masters from different local places,"compare" and return what you don't use.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
But some of the suppliers are selling non-corvette masters and a mix of hodge podge parts.I've seen drum brake masters,masters with reversed line fittings,masters with adapters at the lines,same number masters with different pistons installed and on and on and on !!!
You can't rely on what the parts guy gives you as being correct.
I would go buy several masters from different local places,"compare" and return what you don't use.
Reversed line masters are for disc/drum brakes and if you don't have the part # to match or are unsure, then the largest reservoir always goes to the discs and some have a residual valve installed for the drum side. You can make most work, but it can be a PITA.
I recently got a manual master in a power box.
Thread Starter
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
Ok, the new master cylinder has the casting number and bore of a powered system and it has the shallow hole in the middle of the piston so I am thinking it is the right one. I just kept reading about differences in bore sizes not the size of the hole in the center.
