Geeesh another after market disc brake conversion question

Brakes, Suspension, Rims and Tires

  1. Fredo

    Fredo Member

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    I've decided to buy one of the after market kits for my 66 300. I have had the breaks completely rebuilt with new booster, wheel cylinders and pads less than 1000 miles ago but it still doesn't give me a comfortable feeling driving that land yatch around in city traffic.

    Ive read a bunch of threads and seen a few videos but I'm still confused on master cylinder and booster requirements. My 66 is drum set up but has a a booster on it making it power brakes? The master cylinder is a single pot set up and I believe I need a dual pot with a proportioning valve inline?

    So here's the main question, which kit have folks used that they felt worked well. And will the kits that only come with the master cylinder work with my booster?
    It looks like the top kits are all around $1000.00 with master cylinder.
    Thanks in advance all y'all
     
  2. Turboomni

    Turboomni Old Man with a Hat

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    If working properly drums shine in city traffic. It's when you get them hot with long braking they can get fade like descending a mountain etc. When I first got my 69 Fury I considered going disc but after getting new drum brakes installed I was so happy with them I decided not to. Not knocking disc brakes at all. Are you sure your drums are working properly and have decent quality parts for the rebuild? What does it do in city traffic?
     
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  3. Fredo

    Fredo Member

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    Well I have to admit I just don't like them. I'm old enough to remember driving my dads 56 chevy drum brakes when they got wet or over heated.
    That awful feeling of "Man I hope this thing stops" is something I'd rather do without. I'm just not a fan of the P&P (press and pray) breaking systems.
     
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  4. Imperialist67

    Imperialist67 Senior Member FCBO Gold Member

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    there's a LOT of advice/info. on that subject here, and I'm in no way qualified to bring anything better along on that, my only advice would be to consider the better (than off-the-shelf Chinese made) SHOES that are out there, someone posted a link to what look like promising, high-performance brake shoes that may really help. The OEM asbestos shoes are also a good bet. I also have an inevitable amount of down-town stop-and-go anytime I get my New Yorker out and about, and also find that the drums do just fine for that, even if they squeak a bit...……
     
    Last edited: Feb 24, 2021
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  5. stubs300

    stubs300 Senior Member

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    You didn't mentioned about wheels, do you like and want to keep the 14" or what to get bigger wheels? Because depending on who you go with, most kits require 15" wheels. I went with a 4 wheel disc kit on my 66-300 as I felt the same about the way it braked no matter what I did. Plus the scarcity of parts as time goes on, and I wanted to keep the spinners. The company I used is out of Biz, SSBC, there's many good companies out there. You just have to find your best deal. Good Luck
     
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  6. Turboomni

    Turboomni Old Man with a Hat

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    Yes I can understand that. Just curious is all. There are no doubts to disc brakes advantages.
     
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  7. Mike66Chryslers

    Mike66Chryslers Well-Known Member

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    If you have a vacuum brake booster then yes, you have power brakes. Some will disagree, but you can't use your drum booster with disc brake conversions. You will need to replace the booster with a more powerful one. The factory-correct booster for a 65-68 C-body with discs is getting difficult to find.

    There are different master cylinders available for 4-wheel drum and for disc-drum systems. Even if you decide to stick with 4-wheel drums, it is recommended to replace that single-circuit MC with a dual reservoir one, so your front brakes and rear brakes are on separate hydraulic circuits for safety.

    IMO a lot of the decision on whether discs are worth the effort is how you're going to use the car. One of my '66 Chryslers I have upped the horsepower and also used it as a summer daily driver for several years. That one I upgraded to front discs. My other one has only ever been a fair-weather weekend cruiser. I retained the factory front drums on that one (swapped to dual-reservoir MC) and never had any problems with them aside from maintenance issues as with any brake system.
     
    Last edited: Feb 24, 2021
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  8. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    I am someone who is a firm believer in using the factory disc brake upgrade - 69 - 73 C body disc brake spindles and such, and the correct 65-69 C body disc brake power booster, and 68 and up C body disc brake dual reservoir master cylinder, and I recommend this for the hands down improvement over drum braking capability, especially on the highway and dealing with repeated stops. I am not a fan of the aftermarket systems - too many reports of poor engineering and other issues. Without tooting my own horn too much, I am somewhat an authority on the disc conversion of our C bodies using factory engineered parts. PM me for details.

    I also agree though, that a well set up drum brake system is excellent for in town and 90% of your driving requirements.
    They just suck on the highway past the first hard application.

    HOWEVER, if your newly refreshed drum system feels less than satisfactory, then it may be something as simple as the person who installed them did not arc the shoes to fit the drums. This will result in MUCH LESS braking power than the drum system has potential for, simply because the brake shoes are not contacting the drums as fully as possible. I've seen situations where the shoes are so far out of match to the drums that the reduction in "swept area" (the amount of shoe contacting the drum's surface) had to be in the order of only 30% of what it should have been. Obviously, VERY poor and unsafe braking from an otherwise new system in perfect working order.

    Arcing shoes is an old school practise that is rarely performed these days, since most drum brakes are on the rear of modern cars, and as we know the front brakes do the lion's share of the work. In your case, I would have an "old school - grey beard" mechanic inspect your drums and shoes for fit, and if needed, arc the shoes. You may notice a dramatic improvement right off the bat.

    Yes, the shoes will gradually arc themselves to fit, but it could take a very long time, and overheating of the smaller area can result in glazing of the drums and deterioration of the shoe.

    The other thing to have a look at is to see if the shoes are installed backwards - the results of this are reduced braking performance.
     
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  9. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    I'm not going to agree or disagree with anything written above about drums v. discs, so let's just answer this question.

    From what I've seen, the kits seem to want to use a universal GM style master cylinder with booster and I don't understand why except they don't want to bother researching other options.

    The Mopar stuff is pretty darn good and available. If your booster is good, I would try sourcing a disc brake mc from a later Mopar and that will bolt directly to the existing booster. Bolt pattern is all the same and you won't have to mess around with getting the GM stuff to fit.
     
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  10. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    I agree with everything @Big_John says, up to a point.

    Respectfully, there's a reason there is a Disc booster and a Drum booster from the factory engineering. And I have experienced a disc brake system using both booster on my 66 T&C when I did the conversion for the first time, and it was not as good as I expected. I researched, and put on the correct disc booster. NIGHT AND DAY. I can say WITHOUT A SHADOW OF DOUBT, that using the drum booster on a factory disc system is leaving performance on the table, instead of putting it under your foot. Potentially VERY dangerous.

    Disc systems need more power to fully energize, and a drum booster cannot do that. So, yes, they'll bolt together and work, but there will be a point in which the disc booster will allow the disc system to outperform the identical setup using a drum booster. In my experience, it's a significant difference.

    Look at it this way - the difference could be the the stopping distance required to not kill the clueless 5 year old kid pulls out in front of you on his bicycle, or stuffing your car into the back of the idiot who pulled in front of you and then jammed on the brakes, instead of stopping short of his back bumper and being able to blast him only with the horn, not your whole front end.

    The other thing is - you kill or maim someone, and you're driving a vintage car, you can be fairly sure they're going to examine the mechanical fitness of your vehicle. If they find that your braking system is a hodge-podge of non factory parts, or two systems merged together, and it's deemed that the performance of said system was compromising the overall braking capability of the car, well... the lawyers are going to have a field day.

    I strongly urge everyone (including those who feel the drum booster is fine on a disc system), NOT to do that. Use the correct booster for the job. You'll never regret it, plus your ass will be covered as well.

    FWIW, the factory single diaphragm disc brake booster from mid 70 and up is wider, but will bolt up and perform just fine. You may find that you have an interference however with 65-68 column shift linkages that prevent you from engaging Low 2 or Low 1 on your trans, and will only be able to shift into Drive. If that is OK by you, then that booster is much more readily available.

    No disrespect meant to you @Big_John , as you're highly respected by me, and advice and insight on so many topics here on FCBO is highly regarded. However, I can't agree with the recommendation to use a drum booster on a disc system.
     
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  11. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Point taken and it's something I didn't really think about.

    I think my view is to stay away from the aftermarket GM booster/MC combo and I didn't think it through, having not done this particular conversion. I'm mostly armchair on this one, doing a couple disc conversions with manual brakes and not involving power brakes. The other used Mopar parts and was pretty straightforward.

    Thank you for the correction and paying attention!
     
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  12. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    We're all in this together! :)
     
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  13. Mike66Chryslers

    Mike66Chryslers Well-Known Member

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    If the shoes are installed backwards, you may have extremely grabby brakes. (My Windsor had the front shoes installed backwards when I got it, so I have first-hand experience with this!) The shoe with the shorter friction material should be towards the front of the car.
     
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  14. Steve300

    Steve300 New Member

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    If you can find the 68-73 factory disc setup it will work fine. Problem is finding the parts. I found a set of '69 spindles and brackets on ebay for $200. Looked on rock auto rotors about $40. Problem was finding calipers. Found some RH ones, but could not find any sets. So after talking to Scarecrow I bought their kit MON-D12. Uses 11-3/4" Cordoba rotors, and if you buy their Monster calipers you get the same 2-3/4" dia. piston size as the factory setup. So basically you get the same effective brake setup as the factory, but easier to find parts, no need to change spindles which means no front end re-alignment, as the calipers have a better selection, and more modern pads available. Kit comes with the brackets and rear wheel bearing adapters. Everything was well made, no junk. I looked at a lot of kits and other than Wilwood I feel this is the best setup out there.

    As for the booster there is a 8" dual diaphragm Bendix that is a copy of the factory unit being sold for B & E body. Not sure how much mod is required to fit a c body, but would just be bolt pattern and pushrod length. Beyond that the generic boosters will work is just a matter of again bolt pattern and pushrod length and style, and proper MC selection. Of course it does not have the Mopar "look". A dual will give you about 30% more assist then a single of same size and bigger the diameter the more assist. Main issue is what will fit. I'm working on a 66 300 and a 440 with the cast Mopar valve covers are close to the factory drum booster. Still trying to figure out if I can use a 9" dual booster.
     
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  15. CBODY67

    CBODY67 Old Man with a Hat

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    Well, the FIRST THING in your comments about "wet Chevy brakes" is typical of all Chevy brakes from back then. Drive past a mud puddle and they'd need to get dried-out before they would work again. By observations, CHRYSLER drum brakes are not that way, to the same extent.

    The second thing is that our '66 Newport (power drum brakes) would lock-up ALL four wheels if needed, stock. Had decent fade resistance, too. Care to "eat some steering wheel?" Especially after we'd get the brakes "de-dusted" with an air hose.

    Third thing, what width drum brakes are on the car now? There can be 11x3, 11x2.75, 11x2.5, etc. Wider is better. What brand/type brake linings were put on the car AND have they been "bedded-in" properly?

    Even by 1969, our C-10 pickup had "passable" power drum brakes from the factory. Seemed to fade quickly, too. 11x2, all around. By comparison, the brakes on our '66 Newport were far superior.

    Just some thoughts,
    CBODY67
     
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  16. mr. fix it

    mr. fix it Old Man with a Hat

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    Having reviewed this thread, I too did the 73 disc conversion a few years ago and used the drum booster up until now.

    my experience is that the drum booster works well if the vacuum is at peak suction when engine is cold.

    Also good if you can ease into brake application while driving.
    Quick panic stopping is a different story though required both feel planted down hard.
    Not a good feeling period!

    I have not been able to source any good dual diaphragm boosters because they are like hens teeth.
    Any found were past the rebuilding stage or insanely expensive and still required rebuilding.
    Not a cheap endeavour

    Right now I’m having an aftermarket dual diaphragm booster added which requires a bunch of fiddling around with to find a happy setup
    So far, the mechanics have shortened the pedal push rod and replaced the brake lines, replaced the firewall plate with a manual brake plate as well
    It doesn’t mount flush to the firewall either but relies on brackets which doesn’t look or may all but function is more important than appearances

    once completed I plan to post the results
    image.jpg
     
    Last edited: Feb 25, 2021
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  17. mr. fix it

    mr. fix it Old Man with a Hat

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    One additional comment is to be sure to use proper vacuum hose, not fuel line!.

    It will likely collapse under braking once it is at under hood temperatures.

    I learned this the hard way when a local parts store sold me the fuel line claiming it worked great when it caused me to think I had a defective booster...
     
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  18. Mike66Chryslers

    Mike66Chryslers Well-Known Member

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    Good advice, thanks. A friend of mine is having difficulty with his power brakes not working properly. I told him I'd help him diagnose it when he gets the car out in the spring. I'll keep this in mind when we start digging into it.
     
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  19. BIGBARNEYCARS

    BIGBARNEYCARS Senior Member FCBO Gold Member

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    If you follow the Read and Research approach, the factory stuff is out there in new, used, or remanufactured condition, and way less expensive then the "KITS" That is someone else's brain child. I'll chalenge you by asking you a simple question without meaning or wanting to offend you. Can you hold a factory Proportioning Valve in your hand and identify and tag all five ports as to which goes where and hooks up to and does what? Brings us back to my following the R&R approach. Do it and you'll have the knowledge to have your own opinion and trust in your own decision and feel comfortable with it, Jer
     
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  20. Fredo

    Fredo Member

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    Well folks, first thank each and everyone of you for your thoughts, opinions and input. It has helped me greatly.
    With that said I contacted SSBC (although I read they were closed) and spoke to one of the techs there about my needs.
    I am confidant they have what I need to make my stopping dreams come true. So I ordered a full set up including MC and booster. No offense to those folks that talked about the benefits of Chrysler parts as a retrofit. I think I'm just getting a little too old (lazy) to go through the extra hassle of assembling a set up myself. I will definitely update you folks on how it goes. I expect my parts to be here in about 4 weeks or so.
    For those interested, it came out to a bit over $1200.00 which is a little more than my budget...oh well that's the wife's problem since she does the books around the homestead.
    Thank you all again for the information and education.
     
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