Hi Everyone. I just got home from the slant 6 race in North Wilkesboro. While I was there the master cylinder began to fail. I need to replace the master cylinder but I would like to address a few other brake issues at the same time. the car is a 1974 plymouth Duster with manual brakes and front discs. All factory equipment.

#1 rear wheels lock up way to early
#2 Pedal pushes a little harder than I would like. My dart with manual brakes seemed to push significantly easier. This car is for Whitney to drive so slightly easier braking would be nice. I am not a big fan of the power brakes though and would like to stay away from that if possible.

I would like to order the parts and get started on this before clay city next month and would appreciate any thoughts/suggestions or even suggested part numbers.

Thanks in advance for the help.

Ryan

_________________
Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

Rear lockup, see here for the info on how to fix most of this problem.

Easier brake pedal: swap in a set of 1976+ front brake calipers with the 2.75" piston diameter (Raybestos RC4103 and RC4104) rather than the 2.6" units you have now. Inexpensive at RockAuto. This will also fix the rest of the early rear lockup problem.

(Of course all this is contingent on the brake system being in fundamentally good repair)

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks a lot Dan, I was hoping you would see this post. I figured you'd know what to do with the brakes. That was exactly the info I was looking for. I will go ahead and get the calipers and the 3/4 wheel cylinders. Did you have a suggestion for the master cylinder or should I just stick with the factory bore size? Thanks again!

Ryan

_________________
Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best

Yep, what Dan said. You can get a 15/16" MC if you really need it, in the aluminum 2 bolt variety, and get an adapter plate. Alum MCs came in different sizes, so you would have to find a small bore one from a trusted source.

My guess is once you do the smaller rear whl cyls and the larger front caliper piston diam, you will have much less effort and won't have to mess with the MC.

Cheers,

Lou

_________________
Home of Slant6-powered fun machines since 1988

Yup, Lou's got it: with the larger front calipers and smaller rear wheel cylinders pedal effort will be much more appropriate (once the new front disc pads bed-in).

I'd go for the 13/16" rear wheel cylinders, not the 3/4".

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ok Great, Thanks guys. I will get the 13/16 wheel cylinders and a new factory replacement size master cylinder then. I appreciate the help. I will go order this stuff right now.

_________________
Ryan Covalt
62 Plymouth Valiant Race Car 2170# 11.008 @ 117.65 MPH 1/4 Mile Best
72' Dart Swinger Street Car, 4 spd, 3330# 14.061 @96.58 1/4 mile Best