Brake woes (not whoa!) question

My dad just swapped out all of his brake hardware on his 34 coupe. The rears are new 11 x 2 1/4 fords with 1 inch bore wheel cylinders, the fronts are 48 Lincolns 12 x 2 with 1 1/8 bore wheel cylinders. The master cylinder is a late 70's ford truck 1 inch bore manual drum brake master cylinder. It has 10 pound residual valves in the system close to the master cylinder. The brake lines are 3/16. The problem is a very very low pedal. It requires almost 4 inches of travel before it gets hard. The pedal will not pump up and doesn't seem to be spongy. We pulled the drums and the shoes and although not seated yet, they seem to be hitting pretty evenly all the way around. Before it had 40 brakes on it with a fruit jar master cylinder and had a good high pedal, so we don't believe it to be a pedal ratio problem. The brakes seemed to bleed well, but he did not bench bleed the master cylinder before installing it...any ideas on what to check? We are going to adjust the brakes to fully locked in the morning and see it that gets a high pedal, but if this doesn't change much where should we look? Master cylinder? Could there still be air in the master cylinder since it wasn't bench bled? It is under the floor. I've got the same set-up on both of my cars except I am running the corvette style master cylinder on one and I think the other may be a dodge master cylinder. Are all 1 inch bore cylinders basically equally other than mounts and reservoir size? Thanks for any advice. Tim

 

If the pedal is getting hard even at a lower placement, I would say you are on the right path adjusting up the shoes first. Typically if there is air in the lines the feel is more "spongy" rather then hard.

 

Well, this morning we pressure bled the system and didn't seem to get any air. Then we ran the brake adjuster out and locked the wheels and the pedal jumped up about two inches. His car has Buick drums and we started checking and they are turned to the max...so maybe the shoes are just not hitting well. Since he'll have this car forever, we are going to put another set of drums on it. I have a pair that have never been turned and should clean up at .025 or less. Maybe that will allow the shoes to seat sooner and get the pedal up where it belongs. If anyone has any other suggestions fire away. Tim

 

If you have it bled well and the travel is still long, possibly there is not enough fluid volume in the MC stroke. If the pedal effort is fairly low after you get a good pedal, you may want to consider a slightly larger MC.

The 87 Lincoln LSC has an aluminum (sometimes iron) 1 1/8" MC that would displace more volume at the cost of higher pedal effort. A shorter stroke would be required for the same volume of fluid. It is roughly the same dimension as the MC you are using now.

 

The Lincoln brakes need to have the top anchor adjusted when installing new lining. Do this by taping a 12", .010 feeler gauge across the top of the primary and secondary shoes, and adjusting the top anchor up as far as it will go, then tighten the nut down, the adjust the starwheel for the final adjustment.

 

Adjust your drums all the way out where you can barely spin the hub, bleed your brakes then back the star wheel off 8 clicks. That should let you know if it's the shoe drum clearence issue and will also seat the shoes to the drums.
If the pedal still feels like it travels to far before inguageing try adjusting the the shaft from the pedel to the master.

 

Dad loosened the top anchor pin when when he made the intial adjustment. The way he did it was by loosening the anchor pin and then running the bottom adjuster out and locking the wheel, then tightened the anchor pin and backed the bottom adjuster off.

 

The master cylinder rod was adjusted at set-up for the proper free play. It takes about 20 clicks of the star wheel to get them free enough that the brakes have a slight drag, anything less and he is afraid that the shoes will get too hot from dragging to hard.