Pray tell, why do you want a larger bore master cylinder?

 

Compensates for the increase in pedal stroke when converting to disc from drum. The disc piston has a higher volume than a slave cylinder.

 

will also require more pedal force to create equal braking force of the stock master cylinder. so you'll be working harder to achieve equal braking. this is why manual brakes have a smaller MC bore.

 

The bore is only slightly larger.

 

i hear you. just something to think about. bigger isn't always better. a 1/4" bigger bore will require about 75% greater force at the pedal to generate equivalent line pressure/braking force of the smaller bore. it's much more of an issue in manual braking. so if your booster ever goes out, you'll really know it!

 

Been driving junk all my life, no worries whatever may come!

 

Keep us posted as you go so the rest of this crowd that's following can just break column and avoid whatever pitfalls you happen to find.

 

My machinist friend told me to thread the little nipple cap in the outlet port of the rear brake part of the master cylinder, yank it out and take out the check valve. Then buy a rebuild kit just to get a new insert and reinstall.


I probably won't this time. I need to get it up like yesterday! A friend that works at Granger is giving me a brand new garage cabinet that has a few scratches. Gotta get it this week, and firewood this weekend.

 

Update:
Got the school bus master cylinder on and the brakes bled and drove the truck today.
Have less than an inch of pedal travel before the brakes engage, but it does take more effort because the larger bore piston.
The brakes weren't this rock solid when the truck was new. There is no light pedal pressure creep like there always has been.


I may look for a compatible master cylinder that is made for 4 wheel disk in the future if I can't live with the increased effort, maybe an older 'Vette unit.


I warped one of the brackets a little welding to it so I have a little bit of rubbing. If it continues I will pull the caliper and head/bend until it is perfect.


Found one e-brake setup, right side, in Arizona. Got it coming. Still looking for the left side.


Overall, very happy I did it.