Converting to 4-wheel power disc, what distribution block do I need?

[funknut]

Apologies for the newbie question, but I've done a fair bit of searching and still can't figure it out.

I'm converting from manual drum brakes to 4-wheel disc and am having trouble figuring out which distribution block I need.  I ordered the left one from Mancini and it has the spring valve in the top, my original one is on the right.

Not sure it matters, but I'm installing the Tallon hydraboost with a Wilwood m/c.

[Dino]

Either you install the one on the left which has a built in prop valve and hope it works for you, or install the one on the right which is a plain divider and add a manual prop valve. I say try the one on the left and see how it goes. You can always replace it with the other one and add a valve if needed.

[Kern Dog]

Four wheel drum systems used no proportioning because the wheel cylinder sizes dictated the proportioning alone. A front disc/rear drum NEEDS the valve on the left to provide the proportioning and to reduce the chance or rear wheel lockup.
A four wheel disc system, if the caliper sizes are staggered with the right amount of bias, need NO proportioning in the form of a valve. They merely need a distribution block as seen on the right.
Example: A car with front calipers with a caliper piston of, say....2.75 needs a rear caliper size that is smaller than 2.0. My Charger has a 2.75" bore front caliper with a rear caliper sized at 1.5". NO proportioning by way of a valve or a junction block. JUst a distribution block from a 4 wheel drum car. 

[Dino]

i had a long discussion with another member here (with plenty knowledge on braking systems) about that and he recommended a manual prop valve as it's a long shot that the pressure will be equal front to back. But it doesn't hurt to try either way.

[funknut]

Thanks guys, makes a lot of sense.  I think I finally get it now.

While I'm in it this deep I may just go with a manual prop valve and save myself some guesswork down the line.

[Kern Dog]

i had a long discussion with another member here (with plenty knowledge on braking systems) about that and he recommended a manual prop valve as it's a long shot that the pressure will be equal front to back. But it doesn't hurt to try either way.

I agree that I may have been lucky with my setup. The only reason that I can see to have a knob type adjustable prop valve is to reduce pressure to the rear to prevent lockup. If the fronts lock first, there is nothing to be gained by reducing pressure to the rear. 

[Dino]

i had a long discussion with another member here (with plenty knowledge on braking systems) about that and he recommended a manual prop valve as it's a long shot that the pressure will be equal front to back. But it doesn't hurt to try either way.

I agree that I may have been lucky with my setup. The only reason that I can see to have a knob type adjustable prop valve is to reduce pressure to the rear to prevent lockup. If the fronts lock first, there is nothing to be gained by reducing pressure to the rear. 

True. And all we can do is some panic stops and make sure all wheels lock and the car tracks straight. If it does, you're good to go.

[John_Kunkel]

Problem with a manual prop valve is, which system do you install it in? Hard to predict whether the front or rear will need proportioning if any.

[Dino]

What about a manual prop valve front and rear? They're pretty cheap. Would it hurt?

[c00nhunterjoe]

I also run the stock 4 wheel manual drum distribution block with disc/drum brakes with no issues.

[invincibleextremes]

Speedway motors sells a $35 proportioning valve thats compact and works amazing.  Also clearly marked, we used it on my cousins 66 Buick skylark and it sits under the dash...  we can throw it in park, reach under, turn off rear brakes entirely and burn the back tires to the ground almost, then back off the adjustment and keep driving with the brakes working like they should....

[invincibleextremes]

Oh and I forgot to mention, I just use a brass T for the front, and that's it.  No other blocks needed.