Yet another brake question...

[FoMoCoGuy]

Hi guys, new to the site. Im working on a 64 chevy c10 for someone.Im in the middle of doing a manual drum/drum conversion to a power drum/drum conversion. He has provided all the parts and says theyre off of a 60-66 with power drum brakes. He wants to keep it a single pot master cyl. Ive got the booster hooked up and the master cyl bled, but im having trouble with touchy brakes. I mean real touchy. all you have to do is just touch the pedal and it just about locks up.

Ive tried adjusting the intermediate rod between the booster and master, and i already adjusted the pedal rod so that it is against the rubber stop.

The problem is, I can't quite figure out what to do about the brakes being so touchy. Is there another point of adjustment on these? I'm not at all familiar with these trucks, in fact it is the first Cheverolet I've actually worked on.

Thanks for any help in advance, guys.

[Captainfab]

Welcome to the forum

Do you have the pushrod attached to the brake pedal at the original location, or is it lower? You say you have adjusted the pushrod to position the pedal against the rubber stop. I would try backing that off some, and see if that helps.

[slepysal]

Originally Posted by Captainfab

Welcome to the forum

Do you have the pushrod attached to the brake pedal at the original location, or is it lower? You say you have adjusted the pushrod to position the pedal against the rubber stop. I would try backing that off some, and see if that helps.

Thats what I was thinking too you may need to drill a new hole below the original one.
see post # 13 on the link below
http://67-72chevytrucks.com/vboard/s...t=ball+bearing

[FoMoCoGuy]

Thanks for the welcome, Capt. fab.

I have not re positioned the rod by drilling holes in the pedal. It is still attached in the factory position. I probably do that today and see what happens.

I tried leaving the pedal at the original height, but it was about an inch off the rubber stop (foot off brake).

[FoMoCoGuy]

Well, I re adjusted the Rod between the booster and master, seems i had it a little too tight. We now have 3-4 inches of pedal travel, but it still grabs a little.

I pulled all the wheels, and found 2 out of round drums, 1 loose wheel bearing in the front, and one massive axle seal leak. The owner says he keeps going through axle seals on the pass side rear. Theres no play in the bearing so I'm thinking its either the axle is grooved or the seal install process is incorrect.

The owner says the axle housing is late 63/early 64, would this axle be different from the factory axle in other 60-66 trucks? Its not the original axle to the vehicle.

[Captainfab]

The main difference between the '63 truck 12 bolt and the '64 and up truck 12 bolt, is that the '63 has pressed on backing plates. The '64 and up used a welded on backing plate flange with the backing plate bolted to that. I don't remember if the '63 12 bolt used a different wheel bearing and seal or not.

Originally Posted by FoMoCoGuy

Well, I re adjusted the Rod between the booster and master, seems i had it a little too tight. We now have 3-4 inches of pedal travel, but it still grabs a little.

I pulled all the wheels, and found 2 out of round drums, 1 loose wheel bearing in the front, and one massive axle seal leak. The owner says he keeps going through axle seals on the pass side rear. Theres no play in the bearing so I'm thinking its either the axle is grooved or the seal install process is incorrect.

The owner says the axle housing is late 63/early 64, would this axle be different from the factory axle in other 60-66 trucks? Its not the original axle to the vehicle.

[quest]

I think if you are applying a power boost to a system that was originally engineered to work without it you may be overpowering it. Do you know if the inside diameter of the hyd lines and wheel cylinders and master cyl are the same on the current truck as the one that the booster came from? Is the booster sized properly for this application? How many inches of vac are being applied compared to the original application? Try a vac line restriction by partially pinching off the line or intentionally creating a vac leak to the booster to reduce vac to it and see how the brakes react. Maybe you need a smaller booster or less vac going to it? Do you have the master that was on the booster in the other truck?

[FoMoCoGuy]

Well just did a quick search on Autozone.com and compaired part numbers for the 63 and 64 trucks, they use the same seals.

I would assume that the lines and booster diameter are the same, seeing as the booster/master assy (new master, used booster) came from a 60-66 c10. The truck does have a 350 swapped in, mildly built with a cam (not too nasty, still idles smooth). I have vacuum tapped in off of a port on the back of the carb.

[quest]

Possibly it is the pedal geometry then but I would still try restricting the vac and see what happens. Are the brakes the same diameter as the donor truck or smaller?
Hope you find the fix.

[tincan1966]

If you've got a rear grease seal leaking, loose bearings and out of round drums, you're brakes are going to not work correctly.
There are some kits available for the axle seals that have an offset lip on the seal to help with sealing issues. There are also repair sleeves, similiar to what you use on a harmonic balancer. You may have to internet search for these, as not alot of the kids at the parts stores have a clue how to find them.
I'll do some searching and see if I can find something to help.