Need help with braking issues.

[RTG_RACING]

My truck is a 1968 F100 2wd short bed with manual drums. I have an issue where the truck doesn't slow down as fast as I think it should. I installed a new master but that didn't seem to help much. It has a firm pedal but they just don't seem to grab. I have cleaned and adjusted the brakes and all the linings look good. Good flow when bleeding them. Not sure what else to try.

[sargentrs]

Your first sentence is the primary reason Stopping a 4000# vehicle at 50 mph with manual drum brakes without locking up is a slow, gentle process. I always start braking a long way from the target. Also, be wary of the brake shoes you buy. Remember, you're dealing with 50 yr old engineering. Do you really need the platinum ceramic diamond encrusted brake shoes or are they engineered for an application not suited to ours and actually function less efficiently because if it. Did you break in/bed your shoes properly? Failure to do so may cause glazing and reduce your stopping power. https://www.wagnerbrake.com/technical/t ... ak-in.html

[jzjames]

Yes, do early braking. Don’t drive where you need to brake all the time - even in a new vehicle.

Are the shoes recently new? I’ve found out new brake shoes take a little while to get matched in to the drums real good. Then the brakes will stop better.

(new shoes can be installed backwards with the larger-surface shoe toward the front. That will cause poor braking).
Are the soft lines fairly new?

[RTG_RACING]

Shoes are a few years old. Just normal old shoes nothing special. I know they are installed in the correct orientation. My issue is that I can't get them to actually lock up. I have everything to swap it to disk except time. I don't want to take it apart and not have it ready for HRPT so I am just trying to make them better for now.

[sargentrs]

Are you sure your new master cylinder has the correct bore size? Should be 1". A larger bore will cause poorer brake performance.