The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1960 - 1966 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-20-2021, 07:59 PM   #1
oldtrux
Registered User
 
oldtrux's Avatar
 
Join Date: Jul 2010
Location: Bancroft, ontario
Posts: 550
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
oldtrux is offline   Reply With Quote
Old 10-21-2021, 04:26 AM   #2
The Rocknrod
Moderator

 
The Rocknrod's Avatar
 
Join Date: Aug 2011
Location: China Spring, TX
Posts: 7,280
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.
The Rocknrod is offline   Reply With Quote
Old 10-21-2021, 08:33 AM   #3
MikeB
Senior Member
 
MikeB's Avatar
 
Join Date: Jul 2000
Location: North Texas
Posts: 3,378
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!
__________________
Mike
1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes.
1982 C10 SWB -- sold
1981 C10 Silverado LWB -- sold, but wish I still had it!
1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming.
Retired as a factory automation products salesman.
Worked part-time over the years for an engine builder and a classic car repair shop.
Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

Last edited by MikeB; 10-21-2021 at 08:49 AM.
MikeB is offline   Reply With Quote
Old 10-21-2021, 10:29 AM   #4
SkinnyG
Registered User
 
SkinnyG's Avatar
 
Join Date: Feb 2012
Location: Beautiful BC, Canada, eh?!
Posts: 2,161
Re: thoughts on master bore size?

What's the difference in pedal ratio between power and manual brakes on these trucks??
__________________
1961 Apache: "Grabber Orange" Shortboxed, pancake, step-notch, air-ride, boosted-LS
1977 Silverado: Shortboxed & dropped, potato-potato
V8 Pontiac Firefly (Chevy Sprint): The ultimate engine swap: 5.7L in a 1.0L bag
Lotus Super 7 Replica: Scratch-built street-legal rollerskate
SkinnyG is offline   Reply With Quote
Old 10-21-2021, 11:09 AM   #5
oldtrux
Registered User
 
oldtrux's Avatar
 
Join Date: Jul 2010
Location: Bancroft, ontario
Posts: 550
Re: thoughts on master bore size?

Great info guys!! Thank you very much.
oldtrux is offline   Reply With Quote
Old 10-21-2021, 11:40 AM   #6
The Rocknrod
Moderator

 
The Rocknrod's Avatar
 
Join Date: Aug 2011
Location: China Spring, TX
Posts: 7,280
Re: thoughts on master bore size?

Quote:
Originally Posted by SkinnyG View Post
What's the difference in pedal ratio between power and manual brakes on these trucks??
I used this - https://techtalk.mpbrakes.com/how-to...ng-pedal-ratio
The Rocknrod is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 11:27 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com