Slant *        6        Forum
Home Home Home
The Place to Go for Slant Six Info!
Click here to help support the Slant Six Forum!
It is currently Sun Jan 24, 2021 1:20 am

All times are UTC-08:00




Post new topic  Reply to topic  [ 7 posts ] 
Author Message
PostPosted: Sun Sep 15, 2019 11:04 am 
Offline
2 BBL ''SuperSix''

Joined: Wed Dec 21, 2016 3:22 pm
Posts: 13
Location: Walnut Creek, CA
Car Model:
Attachment:
20413991_10155082413144495_7475353845489679541_o.jpg
20413991_10155082413144495_7475353845489679541_o.jpg [ 163.19 KiB | Viewed 2816 times ]
Hi all, my 63 valiant 24 hours of lemons racecar is a original power drum brake car that currently runs later kelsey hayes small bolt pattern drums. It has been converted to the appropriate disk master cylinder and works perfectly!!

However... The power brake systems feel and modulation leaves something to be desired when road racing on track.

What do I need to do to convert the car to manual brakes? I'm guessing I just move the master to the firewall and then need a new rod, but I want to make sure I'm not missing anything.

I already have non power kelsey hayes disks on my 71 valiant street car so I'm happy with how that setup feels.

Anyone have manual brakes and want a power setup? Maybe we could swap parts? I'm in the SF bay area.

Thanks for any input/advice,

-Jon


Top
   
PostPosted: Sun Sep 15, 2019 7:11 pm 
Offline
Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6189
Location: So California
Car Model: 64 Plymouth Valiant
I think the power master cylinder is a larger bore than the manual.

Not sure about Mopar's, but with GM the pedal ratio was different between manual and power (more leverage for manual).

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

8)


Top
   
PostPosted: Mon Sep 16, 2019 6:02 am 
Offline
Turbo EFI
User avatar

Joined: Mon Jan 12, 2015 5:55 am
Posts: 1111
Location: Brightwood, VA
Car Model: 1965 Plymouth Belvedere I
some brake pedal levers have two holes where the M/C rod attaches, one for power, one for manual. If you aren't particular about looking 'period correct', the 78-80 Volare/Aspen manual brake master cylinder should work. The ones I have seen come with the rod attached. It is aluminum with a plastic reservoir. Weighs in at 2.4 lbs, so it's a weight saver over power brakes. It is a two bolt mount, if you want to stay with the 4 bolt mount, the 76Volare/Aspen manual master cylinder is cast iron and has a 4 bolt mount. I use this one on my 65 Fury (manual disk brakes) and my 65 Belvedere (manual disk brakes). I have been using both for years now with no problems.

_________________
-MattMan
Strive for Excellence, not Perfection.
Image


Top
   
PostPosted: Mon Sep 16, 2019 6:06 am 
Offline
Board Sponsor & Moderator
User avatar

Joined: Mon Oct 21, 2002 11:08 am
Posts: 14665
Location: Blacksburg, VA
Car Model:
You should only need the brake pushrod from a manual brake car. Or, you can buy or make adjustable ones to put the pedal where you want it. Late model alum masters such as what Badvert suggests work well. You might talk to Cass at Doctordiff.com as I believe he has several bore diameters available. I would say go for 15/16" or maybe up to 1.032" bore size for good modulation. Do not go with the biggest bore for racing, IMHO.

Lou

_________________
"You mean you still have a Slant 6 in that thing?"


Top
   
PostPosted: Tue Sep 17, 2019 11:32 am 
Offline
EFI Slant 6

Joined: Wed Sep 10, 2003 7:15 am
Posts: 282
Location: N. California
Car Model:
blown340 wrote:
What do I need to do to convert the car to manual brakes? I'm guessing I just move the master to the firewall and then need a new rod,

You might want to include a photo of that mechanism, so folks know what you're talking about. If it's the same as the one I had on a 66 A-body, it's a contraption that reduces the mechanical advantage so that the brake pedal doesn't push as hard, so that the booster can make up the difference, thus getting you back to normal. I always thought it was an ingenious engineering solution, and also a lame excuse, for how to add power brakes to a car that doesn't need them but the customer demands it.

And my suspicion was that it could allow the exact same master cylinder to apply to either approach. I never owned that car long enough to check that theory out.

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.


Top
   
PostPosted: Tue Sep 17, 2019 9:15 pm 
Offline
Turbo EFI
User avatar

Joined: Fri Dec 30, 2005 2:49 pm
Posts: 1001
Location: Houston, TX
Car Model:
I think for the later A-bodies (71' and up?) the power brake master was a smaller diameter (15/16") than the manual master (1-1/32") due to the reduced mechanical advantage of the power brake pedal assembly. No idea why Chrysler did it that way. But for '70 and back A-bodies, I thought all master cylinders had a 1" bore regardless of being power or manual. Would a '63 Valiant actually use a different pedal assembly for power brakes?

What diameter master cylinder are you using now? We use the big 1-1/32" bore MC on our manual disc (originally manual drum) '64 Dart. Some people who've driven the Dart have complained about the stiff/high-effort brake pedal, but I prefer it. We also use the larger of the two single-piston front calipers (2.75" diameter piston). I don't know how the effective piston area on the Kelsey-Hayes discs compares.

If you need to buy a new pushrod anyway, you can get an adjustable one from Dr. Diff. That'll give you the flexibility to install an adapter for the later 2-bolt master cylinder. We did this a while back because we got tired of the dodgy parts quality that we kept seeing in the 4-bolt units. Availability for the older parts is probably only going to get worse...

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing


Top
   
PostPosted: Sat Sep 21, 2019 9:41 pm 
Offline
2 BBL ''SuperSix''

Joined: Wed Dec 21, 2016 3:22 pm
Posts: 13
Location: Walnut Creek, CA
Car Model:
Thanks everyone. I'll try to get some pics of the brake pedal attachment as well as the firewall linkage.

-Jon


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 7 posts ] 

All times are UTC-08:00


Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited