Low cost OEM MC's for bore size test purposes

[Hydratech®]

FYI - I see people spending all kinds of money on expensive master cylinders, swapping them out for different bore sizes for test purposes to see what / if any improvements are to be had (brake feel tuning purposes). Here are some super low cost OE GM MC's that you should be aware of to use for initial bore size swap out test purposes:

7/8" bore manual brake: RAYBESTOS MC39027
(1977 Chevy Monza)
WARNING: This MC does NOT have the deep MC pushrod hole. You CAN drill the piston for a deeper pushrod hole, use a rubber boot to make sure the brake pedal rod doesn't accidentally fall out, or rig up a brake pedal rod retainer of sorts.

http://piratejack.net/master-cylinder-manual-rod-boot/

Here you can see how www.mpbrakes.com (Master Power Brake Company) takes late model MC's that are equipped with the short rod / shallow MC pushrod and then drills them for the deep pushrod hole for manual brake usage:

https://www.mpbrakes.com/images/MC39...earM-Large.jpg

BTW - You are looking at a 2000 +/- model year US S-10 MC that has been drilled for manual brake usage in the image link above.

15/16" bore manual brake: CARDONE SELECT 131639
(1977 Chevy Malibu - deep MC pushrod hole)
(Baer used to supply these with their braking systems years ago)

1" bore manual brake: CARDONE SELECT 131371
(1968 - 1976 C3 Corvette - deep MC pushrod hole)

Once you prove out what MC bore size you may like best, THEN spend the money on a "bling" MC if desired.

Oh, and the general rule with these earlier model GM MC's is the 1/2" port is for the front brakes, and the 9/16" port is for the rear brakes (mentioning this because some MC's are reversed from others as far as which port is which). There are some exceptions...