Brake distribution block help

[70383ChargerSE]

Good evening,

I am in need of some help and advice. I have a 70 Charger that has a Wilwood brake front disc conversion with 4 piston calipers and 11" rear drums. It has the aluminum 15/16 manual brake master cylinder.

The car was original 4 sheel drum brakes.

The car has spongy brake pedal and I have bench bled the master cylinder off the car and bled the system on the car twice with no luck. I do not have a leak.

I do not have the 2lb or 10lb residual valves in between the master cylinder and the proportioning valve as I have read about in previous posts.

Rear wheel cylinders are new from my local parts store.

Attached is a photo of my distribution block. Do you know if this is correct?

In regards to where the lines are going it is the following:

So on the adjustable proportioning valve we have an "in" and "out" line.

The "in" line is going to the front port of the master cylinder.

The "out" line is going to bottom right of the distribution block.

The rear port of the master cylinder is going to the the port directly on the top.

The top left port on the distribution goes across the firewall to the passenger caliper.

The top right port on the distribution block goes to the driver caliper.

Bottom left port in the distribution block goes to the rear drum brakes.

It does have an old style wilwood adjustable proportioning valve and do feel the adjustable proportioning valve complicates things and wouldn't be opposed to taking it off if that would make a difference.

This was put together by the previous owner so I really dont know if this was done right.

I just want to improve on this spongy pedal.

Thank you all in advance

 

[Black_Sheep]

That looks like a drum brake distribution block, my GTX has the same one which I left in place when the front drums got swapped for discs. No issues. Wilwood says to turn the adjustable proportioning valve all the way in before bleeding the brakes. I would try that if you haven't already.

Also make sure the rear drum brakes are adjusted correctly as there's a direct correlation to pedal feel.

The master cylinder is higher than the calipers and wheel cylinders, so I don't think you need residual pressure valves.

How Does a Proportioning Valve Work? And How Do You Adjust It?

 

[70383ChargerSE]

Thank you @Black_Sheep I did not know that about the proportioning valve being turned all the way before bleeding.

For clarification, do you mean turn it all the way to the "increase" side or all the other way to the "decrease" side?

 

[Black_Sheep]

Thank you @Black_Sheep I did not know that about the proportioning valve being turned all the way before bleeding.

For clarification, do you mean turn it all the way to the "increase" side or all the other way to the "decrease" side?

View attachment 1996199

Increase, the link in my post is to the instructions on Wilwood's website. The note about bleeding is at the bottom of the page.

 

[70383ChargerSE]

Awesome. Just saw the link. Thank you @Black_Sheep

 

[Bird 426]

Are the Willwood parts new? Why do you have two poportioning valves. Willwood/stock distribution block? I just used the Willwood only. Were you happy with bench bleeding the master, tubes into the fluid? Bleed the calipers out of the top? Got air stuck somewhere. May be time for new lines and some conversion like I had to. Not a nice area for getting the correct line length. Also, overtightening can damage the flares in the brass and aluminum.

 

[70383ChargerSE]

@Bird 426

Thank you for your response. This was done by the previous owner around 2005 or so. I have no idea what they did or why they chose to add an adjustable proportioning valve. This is a regular street car that does not race of any kind so I dont know why am adjustable proportioning valve was installed.

The wilwood brake system on the car is 20 years old so it is obsolete at this point. Yes bled the system twice and potentially need to take a hard look at all of the lines going into the calipers since this is an older system.

I have done a lot of browsing on this forum and I have read from other members that when you have manual disc/drum and the aluminum 15/16 master cylinder it almost is too be expected to have a longer travel/spongy pedal but it just doesnt seem right so here i am just trying to post up pictures and see if I am missing anything.

I do have an aluminum master cylinder that you would get from dr diff or mancini racing.

 

[Kern Dog]

It has been mentioned but I will repeat....
Adjust the rear brakes to where the drum has some slight resistance when turning it. The pedal travel it takes to expand the rear wheel cylinders and drums is often more than most people like.
A 15/16" master cylinder is fine. That is a size that I have on a 4 wheel disc power system car and 3 non power disc drum cars. Pedal feel is great in all of them.
A stock proportioning valve was not precise, the drum/drum distribution block you have is fine because it serves as a junction point and actually has no proportioning function to it. 4 wheel drum cars were designed to use natural proportioning....in short, that means that the system used larger drums, shoes and wheel cylinders up front compared to the rear.
Disc/drum systems and the balance of proportioning the pressures was a hard target to meet. The discs react in a linear manner, the drums (due to the self energizing function) react in an exponential manner. The front discs need higher line pressure to function than the rear wheel cylinders do.
To clarify, your Wilwood system is not obsolete, you can make it work quite well. Take the advice you've been given and report back.
Cheers.

 

[70383ChargerSE]

@kerndog

Thank you so much for your response. I have read a lot of your journey with trial and error on the various brake setups you tried. Thanks for documenting all of that so people like myself can follow along and make informed decisions. We are getting a ton of rain in california so inwill hopefully be able to make these changes on Friday.

 

[Kern Dog]

Oh, I am quite aware of the rain. We are getting plenty up here too.