FE Power Forums
FE Power Forums => Non-FE Discussion Forum => Topic started by: 67428GT500 on June 07, 2019, 06:03:22 PM
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I am not happy with the stopping power of my factory disc brakes. Everything is new/rebuilt. Even stepping on the pedal with a good amount of force. I used the centering tool to keep the distribution valve centered when bleeding and there is no air in the system.
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My 67 Cougar always stopped great. Power brakes?
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Yes. It's a Shelby. Booster Dewy did the Booster. The Master is a new unit from NAPA, The Distribution Block was a New Stainless Steel Brake item, all the lines are new and the residual pressure valve in the rear was rebuilt. There isn't anything that wasn't rebuilt or replaced.
-Keith
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Stock setup 4 piston calipers? First thing see how much vacuum have at the booster. Really need 15" or more at idle.
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I have exactly 15" at idle. Yes, stock KH 4 piston calipers. Rear drum are 11X2.5"
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Well I'd start with the basics have someone apply the brakes and make sure the front and rear brakes apply. The 4 piston calipers tend to seize, but new or rebuilt should not be an issue although if they sat on a shelf long time never know. Bottom line the pistons all should move freely.
Beyond that how is the pedal? If the power booster not working it will be hard. With car off you should be able get 2 or 3 brake applications before exhausting the booster vacuum reserve and pedal getting hard. If not could be a bad check valve at the booster or a bad booster. If you loose the reserve a after a day or two same deal, is leaking.
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No issues with the booster at all. The bias light is out as well. I used the centering tool. The rears are adjusted so they just drag. I am also running Hawk pads.
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Even new parts aren't up to the task sometimes. Are you certain that the mc is the correct one for your application? SSB dist block? I put all new on one of my Mustangs and fought an "impossible to bleed" situation for weeks before just sucking it up and replacing the brand new prop valve w/ a new prop valve. Fixed. Perhaps try replacing the new dist block/rebuilt pressure valve w/ original and see what that does. One more thing to mention is the adjustment of the brake arm and push rod that actuate the pb and the mc. That pushrod dimension is super important for sure. Just my 2 cents.
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It's all new. There is no adjustment on a 1967 Midland booster. The 1967 is a distribution block, not a proportioning valve. It has a simple shuttle valve that works as a safety in the advent of a front or rear leak out. The residual valve in the rear just maintains a slight amount of pressure at the rear drums.
The booster check is brand new, the booster is rebuilt, no leaks at any fittings. Every hose and line is new. The calipers are rebuilt, wheel cylinders are new and all hardware and adjusters. I did have to thin the Hawk pads out on a coarse piece of sandpaper because they were too thick by about .080.
-Keith
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No experience with those pads, but some high performance brake pads don't brake well when cold. Beyond that you may want to drive another '67 to compare how yours brakes. A '67 just does not compare to modern stuff. Heck my 2002 Grand Marquis brakes better... lol
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Well, my Saab nordic convertible I had shipped in has almost 14" brakes on the front and 12" on the back. It shuts down a 3900 lb convertible quite nicely.
I should still be able to lock the brakes up.
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Well stock front discs on a '67 are about 11". A GT500 is about 3400 lbs and likely more than that in reality.
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I should be able to lock the wheels. It won't, not even the rear. I thought it may be the master. I replaced it with a quality non-imported unit.
I think I am going to pick up a set of pressure gauges and start there.
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Well locking up the tire don't know. Depends on how sticky your tires are, road surface, and how fast you are going.
I can tell you this, if the master is faulty it will leak and if you hold the pedal down it will fall away. It should stay firm. If you have the wrong brake pedal or master the pedal will have the wrong pedal travel, but you still will at some point generate the same pressure provided you have enough travel.
Your car should have a 1" bore MC, and the power brake pedal. Correct travel should be about an 1" to 1-1/2" and pedal should be firm. If the pedal is hard and you have to push hard to keep the car from rolling in gear then your booster is not working correctly.
The power brake set up has less leverage then the manual setup so your travel is less, but you need the booster to make it up. If their is air in the lines you will have a spongy pedal.
If it was me I'd start by trying a cheap set of brake pads and scuff the rotors see what that does. I would also verify that the caliper pistons move freely. Stuck or sticking caliper pistons is a common problem. I l know is all new, but is easy to verify.
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I thought about something else. The brake hoses aren't U.S. made. I ran into an issue years ago that when the manufacturer crimped the hose they all but closed the hose off. The fact that the pistons are all the way in the bore and there was about .010 clearance. I also considered that there isn't enough room for fluid to apply enough pressure. I am good with brakes and have never had this kind of issue. At the end of the day it's going to be something so simple it's stupid. -Keith
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I thought about something else. The brake hoses aren't U.S. made. I ran into an issue years ago that when the manufacturer crimped the hose they all but closed the hose off. The fact that the pistons are all the way in the bore and there was about .010 clearance. I also considered that there isn't enough room for fluid to apply enough pressure. I am good with brakes and have never had this kind of issue. At the end of the day it's going to be something so simple it's stupid. -Keith
Room for fluid isn't an issue unless the piston(s) are blocking the feed port. It's all about MC piston area vs wheel piston size. FWIW - I use single piston "Granada" swap disks on both the Mustang and the Falcon (3250 lbs race weight). These are manual disk/drum, 10x2 read drums, organic pads. Stops fine street or strip. I at one time tried metallic embedded front disks, they wouldn't stop for shit nor hold the car in the burnout box. They are still in a box in the shed somewhere, brand new, 20 years later. I put the disks on the car in 1995 and have yet to change pads, been running every other week plus street since then.
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Maybe a bad set of brake pads ? My shop sometimes runs into bad pads or glazed pads when all else checks good but hard to stop and requires lots of pedal effort . Just had a Trailblazer in here for hard to stop and extra pedal effort that ended up being a glazed set of pads that were overheated at some point , had a Dakota in here several months ago for hard to stop and back brakes locking up almost every stop that a new set of rear brake shoes fixed
just a thought
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Good point - made me remember back when I had my 79 T/A. I spent a lot of time pulling the "performance" pads off the car and buffing the surface with a 60 grit flap wheel to bust the glaze off. Can't imagine why I spent so much time keeping the brakes up to snuff... 8)
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At some point as much as I don't want to screw with it being it's a real Shelby I may just go to Wilwoods on the front. Hawk pads are 135.00. I know the ceramics on my other vehicle have to warm up before they get grabby. I even have over-sized rear drums with an 11X 2.75 shoe. Aggravating to say the least being I didn't skimp on anything.
-Keith
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When I converted my '67 Cougar from manual four wheel drums to manual front discs, I consciously went with a 68 setup. I wanted the simpler and cheaper single piston setup. I got a factory front disc setup off of a '68 Cougar and put it on.
I used a Ford Maverick manual front disc master cylinder. For me, it works perfectly.
paulie
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"I am also running Hawk pads."
Well, even Hawk makes many a pad.
I'd try as others have noted another pad. I also have some killer pads in a box for my 12.75" rotor'ed Baer Racing fronts on my '70 Stang that ONLY work on a track after heating up. For my mostly street driving, a softer set work great.
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These were a problem out of the box. They were too thick so I had to actually remove .080 to slide them into the caliper. I checked disc thickness to make sure the NOS rotors weren't out of spec. They are even correct. I called Hawk and they jerked me around because I had them sitting here for 12 months while I was reassembling the shell.
-Keith
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Remove another.080 and see if it helps . You need some gap to have some fluid volume between caliper and pistons or they won’t have a chance to build pressure... or ... get some pads that fit correctly
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FWIW - run Strange Soft Metallic pads on the rear of the dragster (no fronts of course) and haven't had any stopping issues or glazing. And I get hard on the brakes after the finish line. That is the recommended pad for under 150 MPH. The system is a manual MC with single 4 piston S series calipers on the rear - stopping 1660 lbs from around 125 MPH. Might try shopping for a similar type of pad.
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I bought the SSBC kit to test the system. A 50.00 tool I'll probably use once. I have it if I need it at this juncture.
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If you need it, once is more than enough. Proper tool aids diagnosis, leading to a proper repair. Besides, who doesn't want another tool. I have a nice tool for getting the rockers out from under the cam on the 2.3L Pinto/Mustang motors. No 2.3L motors in sight around here, but - you never know when I might need it again.
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The cheapest parts store pads are usually the softest and those stop best, just wear out quicker.
The hard pads are also hard on rotors and you need to be hard on the pedal to stop unless you are road racing where you use the brakes often. The rotors will not get hot in normal driving unless you are hard on the brakes a lot of live in the hills.
But as for what difference it makes a local 90 year old Mary Kay lady still drives the pink 60 Caddy she got for being tops in sales back then. She lives on an island with a wooden bridge with a stop sign at the end and was teriefied ater having the brakes done at a shop and the car skidded so easily.
I drove it and could no believe that huge boat could put me in the windshield at 70mph even with the booster unplugged. With just a light touch on the pedal. A normal stop just skids.
Another elderly lady to the rescue at DV Aldous, a brake place that had been there forever. She knew her stuff. "The shoes are too soft, we can reline them with harder material. Those huge Caddy brake shoes are not available in a wide selection of compounds at parts stores."
I put the harder relined shoes on and what a difference. Now it takes a ten pound push to stop normally where it took a 2 ounce push before.
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POst purchase of the SSBC pressure tool I have about 400lbs of pressure. That won't get it done. It should be at least 1200lbs at a minimum.
I'm leaning towards a bad new NAPA brake master.
-Keith
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it might not have nothing to do with your problem but i recently bought 4 new flexible brake lines.the ones at the wheels and 1 was blocked off inside and 1 more was barely able to drip.i had to take them back and swap them.
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POst purchase of the SSBC pressure tool I have about 400lbs of pressure. That won't get it done. It should be at least 1200lbs at a minimum.
I'm leaning towards a bad new NAPA brake master.
-Keith
What's the bore on that MC? You may have to shop for a MC with a smaller bore. like in the 15/16" or a hair smaller. MCs like a 1" or 1.125 will give a high pedal and low pressure.
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I am running the factory disc/drums on my Shelby. It's a factory cylinder dimensionally. 1"
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You'll pick up line pressure going to 15/16 or 7/8 bore if available. IIRC Ford MCs use the same bolt-to-firewall mounts from 60s through the 80s or 90s. Why some people run Ranger pickup aluminum units.
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When I converted my '67 Cougar from manual four wheel drums to manual front discs, I consciously went with a 68 setup. I wanted the simpler and cheaper single piston setup. I got a factory front disc setup off of a '68 Cougar and put it on.
I used a Ford Maverick manual front disc master cylinder. For me, it works perfectly.
paulie
I have a '65 falcon in my backlog of someday projects, it has the KH 4 piston calipers. Everything I have read says the fixed four piston calipers are superior in performance to the later single piston calipers, I haven't actually driven that car yet (god willing, I will get it finished before I shuffle off this mortal coil ::) ;D ) so I don't have any first hand empirical evidence, but that's what I have heard, from multiple sources.
FWIW, I am putting 2005-up 12.5/11.75 Mustang discs and bullit wheels on my '67 falcon driver.
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You'll pick up line pressure going to 15/16 or 7/8 bore if available. IIRC Ford MCs use the same bolt-to-firewall mounts from 60s through the 80s or 90s. Why some people run Ranger pickup aluminum units.
Whole point of the 1" bore mc and revised pedal leverage point on the power assisted brakes is to reduce the pedal travel. If the power booster is working correctly should generate plenty of pressure.
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Sorry, I should have clarified that those bores are good for manual brake. Power assist is way different - different bore and different pedal leverage as you stated. My bad - I don't use power brakes on anything except the daily driver types.
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Don't blame you, properly set up manual disc work well. Less stuff in the way and no cam low vacuum issues. Only reason for post was to keep discussion in context of what op has so as not to confuse the issue.
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Well, yes. They will bolt to the firewall. However, there are differences with power brakes. The Midland-Ross Booster isn't so forgiving. I don't mind brake size changes. As for the 4 piston calipers: All race oriented brakes are fixed multiple piston calipers that I have seen in use for vintage Fords.
-Keith
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Smaller bore will make more pressure. The 57 Chevy Junkyard Dawg on the Jegs cover we had to reduce MC bore to make it easier to stop with a handicapped driver and 3900 pound package , I agree with the scrap the power brakes too , the few people that drove my Fairlane didn’t realize it didn’t have power brakes until I reminded them
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I'm not scrapping power brakes on a real Shelby. It's out of the question. I do have larger than factory rear drums. 11X2.5. I don't think it factors into the problem being the cylinder is the same size as the original 10X2.5 that came on it. I thought perhaps someone had ran into an oddball situation.
-Keith
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Agree with the not modify on a Shelby. Your parts should work as installed. Especially with the larger rear drums, those should self-engage and work well with the front disks. It's not uncommon these days to have a new MC be faulty in some way - passing fluid internally and such. Or for some reason there is insufficient vacuum assist - may be plenty in the intake but not making it to the booster diaphragm.
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... Or for some reason there is insufficient vacuum assist - may be plenty in the intake but not making it to the booster diaphragm.
I had a leak between the vacuum fitting/check valve at the booster that would only show up when you flexed the hose slightly. It would build plenty of vacuum stationary at idle but lose enough driving to be a problem. Hose twist and reroute to a friendlier angle was the whole fix.
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make sure you bleed both sides of the front calibers , I had the same problem , it is easy to over look the inside bleeder , may have all ready been mentioned
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I am not sure what you mean by both sides of the calipers. The KH four piston calipers only have one bleeder and the cross over line to the other side of the caliper. As with any complete bleed I start with the furthest away wheel. Right rear and the left front side is last. I use the distribution valve centering tool as well. There was no air showing up in the tubing post bleeding. I have the engine out currently and have purchased a new Master cylinder. I am also going to change the two front brake hoses as I don't like they way they are crimped. Perhaps there is some restriction because of the crimps. I have never had a system issue post any rebuild. Once in a while we can't see the trees for the forest so I thought I'd throw the question out to see if something popped up I negated to consider.
-Keith
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it has been awhile sense I have bled the brakes , I thought there was a bleeder on both side , I guess not , but I had air trapped in the caliber , maybe I just broke the line crossing over , but I had what sounds like the same problem you are having . after I got the air out I had good brakes . sorry if I made it worse .
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Brakes are designed to give us fits. ;D The dragster has two calipers, bleeders on both sides of the calipers, one steel line with a T, one small manual 7/8 bore and a pedal. It's "musical caliber bleeders" just to get a good stiff pedal on that car. The MC holds about half a coffee cup but when it's time to start running fresh fluid I buy a quart jug.