66 valiant disk brake conversion??

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KosmicKuda said:
Order a new MC for a 73-76 power disc brake car from any ordinary parts store but run it manually. No need for power brakes unless you are physically limited. This will get you a 7/8 bore and it bolts right in place. Use the pushrod from your existing setup. You will have to fab or buy brakes lines for the MC. I've done this 3 times and you'll love the brake feel with your new K-H discs. No need to get fancy here.
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I went to the auto parts store yesterday and ordered hoses, pads, and a master cyl. I basically ordered the same parts another member had listed... but according to his post, the mc has a 15/16 bore. What difference would a 15/16 bore make compared to a 7/8 bore? Should I have my parts guy get me the 7/8 instead?
 
I just ordered my proportioning valve from inlinetube.com; there were two separate pieces I needed to order..

P/N PR104B - which is the disk brake hold off valve.

P/N BLK245 - which is the proportioning valve itself.

Does anyone have a good diagram of how the plumbing goes?
 
65 Mopar said:
I went to the auto parts store yesterday and ordered hoses, pads, and a master cyl. I basically ordered the same parts another member had listed... but according to his post, the mc has a 15/16 bore. What difference would a 15/16 bore make compared to a 7/8 bore? Should I have my parts guy get me the 7/8 instead?
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The pedal effort for 15/16 will be slightly greater than a 7/8. But it is not worth worrying sbout. There also may be a slightly different proportioning ratio between the front and rear piston diameters.

I have a 68 cuda with manual front 73-75 a body disc's and 10 X 2-1/2 rear drums. I've tried 7/8, 1-1/32 and 1-1/8 on this car with this brake setup. Overall, the feel with the 7/8 was the best. The 1-1/8 gave a VERY hard pedal, too stiff for my taste. Currently using an old Direct Connection 1-1/32 aluminum MC mostly to save weight and it's fine. You can easily measure the bore at the rear of the MC where it meets the firewall.
You also need some means of retaining the pushrod in the MC piston. Either the rubber o-ring or the bolt-on style will do.

I believe simple is better and eliminated the factory safety/proportioning valve. If basically does nothing but turn on the red dash light if there is a leak. My foot can tell me that as the pedal will drop if there is a leak. I plumbed the large chamber of the MC into a simple brass tee on the frame rail. One outlet to the left front and the other to the right front. The smaller MC chamber goes into a Wilwood Summit) adjustable cylinder on the frame rail under the firewall. The outlet goes back to the line feeding the rears. While I was at it, I plumbed a Line-loc into the fronts on the cuda, but not on my /6 Valiant.

It's simple and already set up for practically any future brake system I throw on either of these cars. For instance, I got the Val running last fall with the 9" drums but acquired front K-H disc's over the winter. No change in plumbing required except swapping to a disc brake MC. My 64 Val had a single circuit MC but I used a dual circuit MC for a 67 drum brake Cuda when I got it running last year.

I believe your "brake hold off valve" is not required as it's built into a disc brake MC.
 
You can find cut-away photos/diagrams of the "combination valve", which became standard for front disk cars by the 1970's. It consists of: proportioning valve, pressure imbalance switch, and front metering valve. Your "hold off" valve sounds like the later. Its purpose is to hold-off pressure to the front calipers until the rear shoes have had time to move into contact with the drum. There are aftermarket version w/ adjustable proportioning (always good), and ones I have seen have the imbalance switch. You can wire the later to short to gnd, with the other wire to your dash e-brake lamp (parallel). Can similarly wire a low-reservoir switch to short to gnd.
 
Well I finally got all my parts to finish the brakes. I didn't get many pictures because I was in a rush to get it together once I finally got all the parts! I have to say that I love the disk brakes on the front of this car!! Very big improvement! I also replaced all the brake lines.
 
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65 Mopar said:
View attachment 1715041184 The brakes on my car have to be modified! I have drum all around and want to do disk in the front. The problem I was told from the previous owner is that with the 14" rally rims they don't make a disk that would fit.
So I gues that's my first question..what combo would fit?

I have access to two spindals with new disks and calipers off a 71 or 72 barracuda..but they are large bolt pattern...that would mean I'd have to change my rims if they would even work in the first place???

So I need help from with this.
Thanks ahead of time guys.. :)
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I used the complete set up from SSBC You can choose small or big bolt- can change out later The 14 Inch rallyes fit
 
I didn't want to go thru the trouble of adding disc, I bought a Geo Metro power brake booster
6" dia used the brakes I had, been driving for 4 yrs no problems, booster $30 plus some new tubing,
you really don't notice the booster on the firewall.
Pictures if you want or call 490-220-8954, Madison Oh.
 
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