thoughts on master bore size?
 

i'm trying to decide on 1'' or 1-1/8'' bore size?
disc/drum setup.wilwood 2 piston d52 calipers
8 inch dual diaphram booster
regular compression 283
attention brake guru guys!
thanks Dan

Re: thoughts on master bore size?
 

With manual I'd go with 1". With power I'd go 1-1/8". Don't forget to re-drill your brake pedal arm.

Re: thoughts on master bore size?
 

With a decent size booster like yours and a stock engine making 18"-20" vacuum at idle, I'd say 1-1/8" would be the way to go. 1" might be a bit "grabby" with a booster and lots of vacuum, but you just never know on an aftermarket setup.

I'd skip the fixed "one size fits all" proportioning valve and install a manual valve in the rear brake line. I mean why reduce rear braking power if you don't need to? Start with the valve wide open, and then adjust if necessary to keep the rears from locking up before the fronts during a panic stop.

Also, install a 10psi residual valve in the rear line (after the prop valve) to keep the shoes close to the drums.

I'm not sure if I'd re-drill the pedal to reduce leverage. I did not do that when I converted my manual brake 69 C10 to power brakes back in the 90s. I do have to admit it is just a bit touchy, but I'm used to it.;) I used a stock 71/72 booster & M/C along with spindles, brakes, and power steering parts from a mid-80s C10.

Just have to add that with those Wilwood brakes and pads, along with rear drum brakes in good shape, you could probably go with a 7/8" M/C with NO booster and stand the truck on it's nose!

Re: thoughts on master bore size?
 

What's the difference in pedal ratio between power and manual brakes on these trucks??

Re: thoughts on master bore size?
 

Great info guys!! Thank you very much.

Re: thoughts on master bore size?
 

I used this - https://techtalk.mpbrakes.com/how-to...ng-pedal-ratio