I’m trying to make some headway on my car, but this brake pedal has me stumped. I believe I have way too much travel in the pedal. In fact, it’s 5” off the floor, and when the engine is running, I can easily get it to hit the floor. The pedal travels maybe 3” before I feel any resistance. I should mention this stuff- it’s a 35 plymouth with a Pete and Jakes underfloor pedal assembly. 5:1 ratio. I added an ECI 1” bore remote fill power master with an OTB reservoir on the firewall. I have an ECI front disc brake conversion with 86 Camaro calipers and large Torino rear brake cylinders. I’m running 3/16” hardlines, and have a 10lb residual valve going to the rears. One 14” braided hose at the rear, and two 14” braided hoses at the front. I’ve bled, and rebled the brakes. Bench bled the master twice. Flipped the residual valve around. Switched the lines on the master. I’ve adjusted the pedal almost as far as I can on the rod going into the booster. All that did was make the pedal come up in the car more. Called ECI Friday and Mark told me it sounds like there is a massive air intrusion somewhere. Then he said with my combo, if anything I should have a very firm pedal. He said the pedal should move no more than 3 inches total or so- which is what I want. I questioned should I have a 2lb residual on the front line and he said it’s not necessary since the remote fill is up so high. So... any ideas? Should I think about going to a 1 1/8” bore master? Carry a boat anchor with me perhaps? Or anything else I’m just plain not thinking about? I appreciate any help on this, cuz I’m lost on this.
Brakes get so many posts and are so important that they should get a sub-forum like the traditional hotrod sub-forum.
Does that booster have an adjustable out put rod? It's the rod between the master and the booster. Some careful measuring here will let you know how close the booster's rod will be to the master cylinder's recieving cup. Adjusting the input rod ( between the pedal and booster) will raise and lower the pedal in relation to the floor. Adjusting the booster out put rod will change the free play.
That’s actually a good question. I don’t know to be honest. I didn’t know any boosters had adjustable output rods. I’m gonna have to pull it and take a look. If it does, that could be the problem. Sent from my iPhone using The H.A.M.B. mobile app
That was my thought at first, but hoped there might be something I was overlooking. I’m going to pull the master and see if the output rod is adjustable like 31Vicky mentioned. Sent from my iPhone using The H.A.M.B. mobile app
Well, the booster does have an adjustable tip on the end of the output rod. I threaded it out a little, and it definitely had an effect on the pedal feel. It has much less play and is stiffer, like I want. Now it’s just a matter of figuring out just how much I can get it to extend, in relation to the master. I’ll watch the video you posted from Speedway now, but thank you for your help! I believe it’s exactly what was needed. Sent from my iPhone using The H.A.M.B. mobile app
I battled this earlier this year. Here’s another link for you. http://techtalk.mpbrakes.com/how-to...forget-the-booster-pin-to-master-cylinder-gap Sent from my iPad using The H.A.M.B. mobile app
The distance we generally set the booster output rod or "pin" was .032"-.040", but .020" should be OK as long as you have a good pedal return spring, ensuring full solid return. (The pedal should be able to actually return farther than the booster input push rod allows.) This pin distance should also be checked with vacuum in the booster, about 20"Hg.
Thanks for the input guys! That link David Gersic posted shows a depth gauge MP Brakes sells. It doesn’t look like it’d be hard to make. I think that will at least tell me where I need to be, and if it’s still a soft pedal, I’ll have to look at other options. I probably have it adjusted too far out right now. As it stands- I adjusted it out a bit, and slapped the master back on just to see if it made any improvement. The master was held out by about 1/16” when it seated against the rod, so I’m sure I’ll have to readjust it to the proper length. We shall see tomorrow after I make the depth gauge. Wish me luck and thanks again! Sent from my iPhone using H.A.M.B.
So I got out there and straightened out the depth of the output shaft. I had it out way too far. I rebled the master on the bench. Installed it and rebled the system. Still have a soft pedal. Talked to Trevor at MP Brakes, and he figures the rear wheel cylinders- which are 1”- are too big for the 1” master. He said I really need a larger bore. Here’s the question I have. MP doesn’t sell a remote fill master with a 1 1/8” bore. The ones I’m finding online seem to be aluminum in that size(like wilwood). Is there any reason I shouldn’t use an aluminum master for the street? I mean... I tend to think of aluminum masters as a racing part, not durable enough for street use. Am I just being paranoid? Or does anyone know of a good cast iron 1 1/8” bore remote master? By the way... I don’t have room to fit a standard master with a remote fill top- I tried already. Here’s another thought I just had- can I swap the 1” bore wheel cylinders to a smaller size? My rear brakes are 11” dia. If that matters... And again... any other ideas on how to firm up the pedal that I haven’t thought of? Sent from my iPhone using H.A.M.B.
Do you have a 'combination' valve for the disc/drum brakes? They act like a traffic cop allowing fluids to go and restricting pressures, they are more complicated than a proportioning valve. Most all OEM MC's are aluminum, you're good to go on that account. I'd get an OEM combination valve from a '69 Torino, they had disc front & your 11" rear drum, read up what size MC they had too while you're at it. I'd say 1" is right but you never know.
I don’t have a combo valve on the car. When I was purchasing everything from ECI, Mark told me an “extra one” was not needed. He said the master I was getting had that “built in to the porting of the master” and all I would need was a hold off valve for the front brakes, and a 10 LB residual valve for the drums. But I’ll definitely look into that again. Maybe he was mistaken. And thank you for mentioning the aluminum masters. I actually thought most of not all OEM used cast iron. Haha that’s what I get for thinking Sent from my iPhone using The H.A.M.B. mobile app
Yep. I have a 10 pound ECI residual, mounted maybe 2 inches from the port on the master. I actually had a brain fart when I was first working on the brakes. I had the e-brake pulled, and the shoes weren’t adjusted. So when I sat back and realized that, I went “THATS IT! That has to be what is screwing me up here!” So I adjusted the drums literally right before my original post. The shoes were definitely out of adjustment, but it didn’t help. Sent from my iPhone using The H.A.M.B. mobile app
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