So I got my new brakes buttoned up tonight. Wilwood fronts on my '71 Demon, stock 9" drums in the rear. I bled each of the Dynalite calipers in the front from the two upper bleeders, but not the bottom two on each, if that makes a difference.

I also set the Wilwood adjustable prop valve to counterclockwise, which Wilwood says is full pressure to the calipers, and both the prop valve and the residual valve (10lb) are in the rear brake line circuit.

I drove it out of the driveway, and it seemed like the pads were a little close to the rotor, so I had to give it some gas. Well, I go to make my first hard stop (at around 15mph), and it stopped pretty good. The problem I am having, is that when I let off the brake pedal (I know the piston comes all the way back in the MC as well), even if I'm in first gear, the car doesn't want to start going again. I have to give it gas for it to start moving like it's in drive. Any guesses as to why it's doing this? Thanks.

I was thinking I might try backing off the pressure on the calipers incrementally, but I don't know that it would help the after-braking problem?

Well to start off, I wonder if its your rear brakes (10lb residue valve) thats the real problem. 10lbs sounds like a lot to me, and you did state prop valve was in rear circuit, and are you sure the MC does not have any internal residue valve and are you sure the discs are on the correct circuit on the MC?

Check the pushrod to master cylinder gap. It should be 1/8" I use clay to check the gap. Also, make sure the correct line is going to the front brakes. Most OEM are backwards (front bowl serves the rear brakes, rear bowl to the front). Some Wilwood master cylinders use front to front, back to back.

The rear brake line is in the front, as both indicated on the old MC (an F and R are present over their ports) and Wilwood's instructions.

The prop valve and residual valve are in the rear brake line as well, as indicated by the Wilwood instructions, and 10lb because the rears are 9" drums.

I don't quite understand the "gap". Am I measuring from inside the pushrod where it meets the piston, or what?

I still wonder if it was just a product of me having all the pressure to the calipers. Though I don't know why it won't come back out, unless I have it so the pushrod (which is adjustable) is actually pushed in a bit because the rod length is too short?

Thanks for your help guys, and keep the ideas coming.

update:

I adjusted the prop valve with no luck today. I put it at max pressure in the rear with no luck and then put it at a midpoint. Still nothing. I do, however, see a new problem. I can let the car idle, and it will start going a bit faster than last time, but now after maybe 100 feet, it starts to actually slow down when idling to less than 2mph. I haven't changed anything except the brakes since I drove it before the brake change. Any ideas?

Also, on an unrelated note, I had cranked up the torsion bars (clockwise) to keep the wheel wells away from the tires. We're talking a good seven threads or more. It looked fine after I finished, but one trip around the block, and it settled back to where it was before, almost precisely. I am confused.

Quote:

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I don't quite understand the "gap". Am I measuring from inside the pushrod where it meets the piston, or what?

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Yes, it's the gap between the pushrod that goes through the firewall and pushes the master cylinder piston. It should not be pushing in the MC piston when the pedal is at rest. If you don't have any gap the MC may be applying the brakes all the time.

You can also crack open the caliper bleeder screw to see if the caliper has fluid pressure all the time. If the rotor turns easier after cracking the bleeder you know it's a fluid pressure problem.

alright, a little more of an update:

checked the front calipers, no pressure in them when the brake isn't applied, which is good.

I also checked the pushrod, and it was loose (loctite'd it down and lock washered it), but seemed to be coming all the way out. But even after tightening it, it's still doing the same thing.

I am however noticing that when I slam the brakes (as if in a hard situation), it does not want to start moving after I take the foot off the brake (auto in 'D').

I also noticed something else. Again I tried to correct the camber a bit by cranking the torsion bars up. I got it to a good place, bounced on the hood/bumper to settle it, and it was still good. I drove it around the block and while I was driving, I could see it, the suspension settled down again to where it was before cranking it. But the torsion bar adjusting bolts are still in a position which should show the suspension cranked up. I am so confused...

Interesting - I've had no problem like that but my setup's a little different. I have:

Wilwoods front disc setup for 10" drum spindels, manual
Rear 11" drum brakes off a 74 van
Wilwood prop valve
Modern-style aluminum master cylinder

Are you sure the rears aren't still holding?

I'd remove the residual valve and try a test drive that way, I have no resdiual valve in my set up. It may be too much for the small 9" drums.

I should check the rears - I don't know if maybe the residual valve's too much

It's not that the pads are too close to the shoe, because they're fine when I don't slam the brake. How would you check them otherwise?

bump

Have you checked the rear brakes yet? BTW "pads to close to the shoe" ??? The pads normally rub slightly on the rotors. The rear shoes should just barely touch the drums. When adjusting them you are good when you hear the shoes starting to rub while truning the drum.

I've got a very similar problem.
SSBC front disc conversion, 10" rr drums
My MC, prop valve, and set-up is the same as your Wilwood.
Does your pedal return properly? Mine doesn't. My story is long and complicated, but something I noticed is after I pull the drums and do anything with the rear brakes, the next time I drive it, the pedal returns properly for the first several stops. Then the pedal starts to stick again. I've pulled the MC apart, checked the pushrod length, checked for mechanical binding, etc.
Something is going on with the rear brakes. I think we need to better understand the residual valve(s) in the system. The SSBC rep has been very helpful. I'll let you know if I learn anything new.

sounds good. I wonder if the masters already have some sort of residual valve, and we are getting too much pressure to the rear. I think I am going to try taking out the residual valve in the rear on Sunday. It seems like it's the only thing I haven't changed