Disc brake question
 

My 67 lemans had disc brakes swapped on the front but still has the drum brake block. Unknown small dual diaphragm booster and MC. Does the system need a modern porp valve instead of the block?

It needs a combination valve. Here is one from
Summit

Allstar Performance Brake Combination Valves ALL41040
Brake Combination Valve, Disc Front/Drum Rear, Brass, Natural, Each

Part Number: AAF-ALL41040

3.78 out of 5 stars ( 9 )

In Stock (more than 10 available)

Any vehicles that I've put discs on the front, also got the combo valve from the donor vehicle. So, sure...install a combo valve. Assure that the BRAKE warning light on the dash works as it should. Metering (Holdoff) valve in-line with the front brakes, proportioning valve in-line with the rear brakes, and the safety switch in-between.

The next upgrade would be 11" drums from a newer intermediate car. Stay away from "Flat-Bracket" cheap-junk rear disc conversions.

Did some digging on right stuff detail and inline tube websites. With your info i now understand whats required. I'll have to replace the hard lines. How hard is it to replace the brake line that goes underneath the engine?

https://www.inlinetube.com/products/...MaAsl2EALw_wcB Use a hold off valve like the one in this picture and you can keep the factory lines and block in place. Alot simpler hookup with just one short line to add.

Thanks, see what you're saying. But this car needs hard lines anyway. I did a disc brake conversion on my other car but the engine was out so running the front lines was easy. Anybody swap that front line with the engine and a set of headers in place?

(Sorry misread your post. I thought you were putting rear disk on and I can't delete this post)
when I converted my firebird over to 4 wheel disk I used the original distribution block and added an adjustable proportioning valve like this one to the rear brakes. Works like a champ.
https://www.jegs.com/i/Wilwood/950/260-8419/10002/-1

I think replacing the Right Front line with the engine in the car is difficult. On my Franken car, the P.O had the line running across the rear edge of the xmember so I just did the same thing with the new line. I installed a combo valve when I added discs to my fronts.

George