[quote="cosvega76"][quote="73astregt"]chuck i have a 73 camaro power master in the car now IT has a hard pedal lol! i got the manual camaro master today and i could see the bore register is quite a bit smaller than the one in the car now. ill take a pic of the register bore with the digital calipers tomorrow nite after work so we can compare the pics between the power and the manual. i had an s10 master to start out with and it would not even fit in the booster and the rod cup at all!. im not into making the hole for the master any bigger in the firewall. i cant see why putting a camaro manual master on should give me a hard pedal as thats what its for, manual disc brakes. the rear brakes are a non issue as i have an adjustable prop valve in the rear brake line.
I missed this response since it was in the quote. Sorry! Ok, Fred, let's start from the beginning.
First of all, the reason the S-10 master won't fit in the firewall is because it is a Quick Take Up style of master. This means there is a large bore next to the firewall (31.75mm / 1-1/4") - with the corresponding large register boss - to move a lot of fluid into the Metric (S-10) style caliper to set the pads against the rotor. The Metric style calipers have a 2-1/2" diameter piston with a seal design that pulls the piston and pads away from the rotor to lessen the drag for better fuel economy. When the pads contact the rotor, and the brake fluid pressure reaches a certain point, the quick-take-up valve bypasses the fluid back into the reservoir and the main bore (24mm / 15/16") of the master takes over. Then it responds like the main bore, to pressurize the brake system for normal service brake control.
Next, the Camaro power brake master has a 1-1/8" bore for use with a booster. The Camaro calipers have a 2-15/16" diameter piston with a traditional seal. Since there is no extra clearance to take up to apply the pads, there is no quick-take-up section to the master. But since there is more volume to be displaced, and less pressure required because of the larger caliper piston diameter, the master cylinder bore is larger.
The Camaro manual brake master is similar. It has a 1" bore to allow more pressure to be generated without the use of a booster. But it still is activating the large piston diameter, so the volume and pressure requirements are matched to this caliper. This master will work with the Metric calipers, but their volume requirement is less, since the piston diameter is smaller. But also, since the piston diameter is smaller, it requires more pressure from the master cylinder to create the same braking force. This is why you need a correctly-sized (smaller) master cylinder for proper pedal feel and pressure with manual brakes.
I am intentionally discounting the rear brakes since both vehicles use similarly sized brakes (9-1/2" x 2") with proportionally less difference in the wheel cylinder bore diameter: 7/8" or 3/4" for the S-10, and 7/8" for the Camaro.
Chuck[/quote] read this bad bowtie