• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Another Master Cylinder Question


FBBO Gold Member
FBBO Gold Member
Local time
7:29 AM
Jul 10, 2017
Reaction score
Hello Everyone.

I have an odd situation occurring and I wanted to bounce it off the experts. (hopefully not a repeat question)

When I bleed the rear brakes, the brake fluid in the smaller, front reservoir of the master cylinder decreases.

The front smaller reservoir is piped to the front disc brakes and the larger rear reservoir (nearest the firewall) is piped to the rear brakes with an adjustable proportioning valve piped inline. I'm confused as to why this is happening. I changed the distribution block and confirmed all piping as per instructions. (https://static.summitracing.com/global/images/instructions/sum-760184.pdf)

I'm not using the metering valve, I've plumbed it directly to the left caliper.
Someone in the comments section indicated that he thinks the instructions were wrong - can anyone confirm? (seems to make sense)


Here's the background information (1968 Dodge Charger).
1. Install front disc conversion kit. The Right Stuff (MDC62DC-P).
2. Replace rear brake lines.
3. Install rear disc conversion kit.
4. Replace above proportioning valve.
5. Confirm master booster push rod depth is correct.
5. Bled brakes - continuing to have issues.

Second question - since I've changed my rear drums and it's now a 4 disc setup, do I need a new master cylinder/booster?

With regards to your question about the master cylinder needing to be changed I would have to conclude that it would need to be. Unequal size reservoirs are used with disc/drum systems.
I installed front discs on my '63 , I used the Chrysler aluminum master cylinder with a dedicated proportioning valve assembly I bleed everything normally and it all works as intended.
Not sure what the person was thinking that did the instructions
Hope this is readable
If what you have above is correct, that diagram is totally misleading!
That would explain why my brakes have never worked properly!
Not sure what the person was thinking that did the instructions
Hope this is readable View attachment 1666345
So what you're recommending is to remove the proportioning valve piston assembly and adapt the disc/drum distribution block to disc/disc, instead of buying a new distribution block specifically for disc/disc. Is that correct? If so, great idea!
I would think about putting the fronts direct, and the rear direct with an adjustable style proportioning valve in line. Probably don't even need to use it, with disc/ rear.
Not sure how it will play with your master cylinder.. maybe others can elaborate.
You will lose the light function
Auto Transport Service