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PostPosted: Thu Nov 16, 2017 1:27 pm 
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Turbo Slant 6
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I made a topic about my brake system woes a couple months ago that is now lost. The basic gist of it is that I obliterated the metal piston in a stock single-piston sliding caliper from heat buildup (either from a dragging/sticking caliper or from just racing too damn hard on stock brake components with high-temp fluid). I also had a slow leak out the back of the master cylinder (probably due to crappy remanufactured parts quality).

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To fix it for a race this past weekend, I slapped on another remanufactured parts-store brand master cylinder I had in my garage and another pair of remanufactured sliding M-body calipers (new ones do not appear to be available). I put a little grease on the sliders, as we usually do. I had to track down some extra-thick copper crush washers to get the banjo fittings to seal (Dorman HW9454-10, NAPA UP3878), and I ended up torquing the banjo bolts to 35-40 ft-lbs (DI said the 1979 FSM calls for 19-29), but in the end I got everything to hold pressure without leaks.

The brakes were great at the race this past weekend, better than they've been in years. However, the last time I threw new parts on, the brakes worked just fine for two races before they catastrophically failed at the third race this past summer. So at this point I'm looking for upgrades, possibly for the master cylinder but definitely for the front calipers that will allow me to use new parts that are readily available in good quality. A little extra stopping power wouldn't hurt either, as the car will continue to get faster.

For the master cylinder, you can still get new Raybestos MC36426 (1971-72 A-body w/front discs) and Raybestos MC36412 (1973-77 A/F-body w/front discs). There's also a "Chrysler-conversion" aluminum Wilwood master cylinder that uses the same fittings and isn't much more expensive.

Calipers will be a much more open question. A few people suggested using the Chrysler pin-type calipers rather than the sliding-type as they are less prone to drag. These appear to be available for 73+ B-bodies and possibly others, but these are also only available remanufactured. Lou uses 4-piston Wilwoods on one car, and I want to say some kind of huge Cobra setup on another? Whatever direction I go, I'll need mounting brackets at a minimum. The ability to use off-the-shelf rotors from parts stores/RockAuto would be highly valued.

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PostPosted: Thu Nov 16, 2017 4:17 pm 
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Frank, that picture was over 4mb! You need to compress them to save on space & bandwidth. I changed it for you.

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PostPosted: Thu Nov 16, 2017 7:36 pm 
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Turbo Slant 6
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Sorry, I meant to just hotlink the image from a different host. Do the Img tags on the new forum automatically attach linked images, even from a URL?

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PostPosted: Thu Nov 16, 2017 8:34 pm 
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SpaceFrank wrote:
Sorry, I meant to just hotlink the image from a different host. Do the Img tags on the new forum automatically attach linked images, even from a URL?

You did hotlink it, but the file is still 4mb. We have over 8200 members in 28 different countries, and they don't all have high-speed Internet. It would take several minutes over a slow connection to see it. I was surprised at how long it took to download on my 9mb connection. Better to show a link to the site that it is on and let someone click on it if they want to see it, or put a smaller picture on that site. You could get that down to 250kb easily.

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PostPosted: Thu Nov 16, 2017 9:47 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
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Location: So California
Car Model*: 64 Plymouth Valiant
That was one thing photobucket was good for. Not much data for photos.............

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PostPosted: Thu Nov 16, 2017 9:56 pm 
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Location: Grass Valley, Ca.
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emsvitil wrote:
That was one thing photobucket was good for. Not much data for photos.............

You can currently upload photos here if you can compress them. I am looking for a plug-in that will compress the photo for you.

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PostPosted: Sat Nov 18, 2017 8:31 am 
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Turbo Slant 6

Joined: Tue Mar 16, 2004 6:25 am
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Location: Tompkinsville, KY
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No doubt there are many options brake-wise, but you may not have to abandon your setup just yet.

In your picture, it looks like a phenolic piston in that caliper (looks like it has a thick 'wall' whereas steel pistons look thin by comparison). Or is that pad debris stuck to it that makes it look that way? I can't tell.
In my experience, those do not handle high heat well and will crumble like that.
They also tend to have an insulating effect, keeping more heat in the pad, which is consistent with the damage in the picture.
For whatever reason, rockauto's 'premium' caliper is sold with phenolic pistons.
You would burn the seals out of the caliper long before you would melt a steel piston (rockauto sells them both ways).

Which rotors are you running? You can use off-the-shelf 11.75" rotors (78 New Yorker, for example) for a little more leverage.
All you need is the correct caliper brackets.
The downside here, of course, is the mass. Aftermarket big rotors are spendy but much lighter for reduced unsprung weight and lower inertia.

Also, good ducting can help keep them cool. Even if you already have some, maybe there is room for improvement?
Remember that a vented rotor is a centrifugal fan, so you decide from where you want it to pull air.
Stock dust shields pull some air over the caliper so if they are missing try to aim some airflow at the caliper if possible.
If you have room (sway bar interference?) you can swap the knuckles to put the calipers on the front to make ducting easier.

Finally, even wheels can make a difference. Are you using an open design or solid? Consider how they can affect airflow over the brakes as well. For example, a close-fitting solid wheel (say, a widened steel 14") can restrict exit flow from the rotor.

If any of this is old news, please forgive me, but it's all I've got :lol:

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PostPosted: Sat Nov 18, 2017 11:42 am 
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This is for a Dodge Dakota spindle but it could work for an F body spindle:

http://board.moparts.org/ubbthreads/ubb ... rakes.html

Greg


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PostPosted: Sun Nov 19, 2017 11:45 am 
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Supercharged
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Location: SW Washington
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The pin-type calipers flex the rubber bushings under pressure and destroy pedal feel and increase pedal travel a lot. Sliding calipers do not have this problem. 11.75" rotors are a big help as are brake ducts. You do have brake cooling ducts right? The problem I had road racing was finding a good pad that fit the caliper. There is an adapter to bolt a Wilwood Superlite (and clones) to the disc brake spindle. You must use 11.75" rotors for that, but then the pad selection is good and the pads are large so they last longer.

If you're running 17" wheels you can do 13" Mustang Cobra brakes. http://www.doctordiff.com/cobra-style-1 ... e-kit.html

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PostPosted: Sun Nov 26, 2017 4:05 am 
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Turbo Slant 6
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sixinthehead wrote:
In your picture, it looks like a phenolic piston in that caliper (looks like it has a thick 'wall' whereas steel pistons look thin by comparison). Or is that pad debris stuck to it that makes it look that way? I can't tell.
In my experience, those do not handle high heat well and will crumble like that.
They also tend to have an insulating effect, keeping more heat in the pad, which is consistent with the damage in the picture.
For whatever reason, rockauto's 'premium' caliper is sold with phenolic pistons.
You would burn the seals out of the caliper long before you would melt a steel piston (rockauto sells them both ways).

Okay, you've blown the lid off one of my major assumptions. Back in 2013 when we first started racing this car, I called up the Raybestos technical service line to verify that their calipers for this application (FRC4107 and FRC4108) had metal pistons rather than phenolic. The man I spoke to verified that these remanufactured calipers did indeed use a metal piston. These are the calipers we installed in early 2013 and used until the middle of 2016.

I guess at some point I assumed that if Raybestos was using steel pistons for this application, they must all be that way unless otherwise specified (some of the A-1 Cardone calipers, for example, specify phenolic pistons in the RockAuto description). In 2016, we installed rebuilt Centric calipers; I don't know why, maybe because they were cheaper. These are the calipers we were running when we obliterated one of them as in the photo above. After I read your comment I went straight out to the garage, dug the removed calipers out of the garbage, and put a magnet on them. These pistons are not magnetic. I took a hammer to the one that wasn't obliterated until I chipped a piece off the edge. The hammer made a fairly non-metallic noise when striking it. The newly-exposed fracture surface does not look like steel or even cast iron.

Well @#$!%!

I went back through my email receipts and verified to my relief that the calipers we just installed a few weeks ago are the same Raybestos part numbers we ordered back in February 2013. So unless they've changed something (or the service tech was BSing me all those years ago), we are probably in better shape now than we were. Of course, I'll be unbolting the currently-installed units to verify the composition of the pistons. I may still be in the market for a caliper upgrade at some point, but I think the priority has now dropped compared to other concerns.

I don't know how many times I've told myself to question my assumptions, but I apparently still needed the reminder. Thank you!



To answer some of the other questions, we are already using 11.75" rotors and our wheels are open. We have no dust shields installed. We currently have no brake ducting at all, but we will probably be installing some before our next race (in April). I'll need to see if we can switch our existing calipers around to front-mount since they're currently rear-mounted. Hopefully our crappy Addco sway bar doesn't get in the way.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
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PostPosted: Sun Nov 26, 2017 12:40 pm 
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Turbo Slant 6

Joined: Tue Mar 16, 2004 6:25 am
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That's why this is a great resource. Lots of extra eyes to help us see clearly!

My 65 has an Addco bar along with front-mounted calipers.
I 'adjusted' the bar by bending the ends in an 1" or so and using slightly longer links.
That combination gave me the needed clearance at full lock (which would be rarely used on track anyway :shock: ).

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PostPosted: Wed May 30, 2018 2:13 pm 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 195
Location: Upper So. CA
Car Model*: '65 Valiant 170 T5
FWIW I'm running this m/c on a home made adapter: https://www.summitracing.com/parts/str-b3359ta
Image

Image


With something close these front calipers (mine are the dust booted version with AL pistons) on AR brackets: https://www.summitracing.com/parts/wil- ... /overview/
Image

Getting away from sliding calipers will improve your brake modulation, and going to -3AN brake hoses will help even more.

Be careful with ducting to introduce the cold air only to the center of the rotor and don't blow it across either or both friction surfaces.

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PostPosted: Wed May 30, 2018 8:11 pm 
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Turbo Slant 6
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We ended up converting to the aluminum 2-bolt MC with adapter plate from Dr. Diff, just to be on the safe side as far as parts quality is concerned. I also fabricated and welded up some ludicrously over-engineered reinforcement plates to the firewall to stiffen the whole area up, since the firewall was noticeably bending under hard braking. We left our current Raybestos-remanufactured steel-piston front calipers in place for our last race, and the brakes were better than they'd ever been.

I would love to upgrade to Wilwood 4-piston calipers at some point, but I haven't had any luck finding the AR Engineering adapters. Are these still made?

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
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PostPosted: Thu May 31, 2018 3:30 am 
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Mancini Racing or Magnumforce were selling them for a while. Not sure if they still are. Doctor Diff is probably your friend here as far as upgrades these days?

Lou

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PostPosted: Fri Jun 01, 2018 5:57 am 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 195
Location: Upper So. CA
Car Model*: '65 Valiant 170 T5
Happened to be on the Mancini page yesterday, couldn't find the wilwood caliper brackets. As the owner of a set, courtesy of Matt, I will say that they are pretty heavy nickel plated steel. When I was designing these things for wilwood we used mostly 3/8" thick 6061 T6 aluminum with press-in steel threaded inserts for any threaded holes. That would make a much lighter adapter. This sort of part isn't beyond a skilled home fabricator. I would use Time-serts for any threaded holes.

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