Power to Manual Brakes

F Body General Discussion

  1. Jonnylightening

    Jonnylightening Member

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    I have a 77 Aspen 318 w/ power brakes. What all is involved in swapping to Manual brakes
     
  2. BudW

    BudW Moderator Staff Member

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    If a person is going to used non-factory (aftermarket or Mopar Performance) small block valve covers or going big block – you will have to either remove the power brake booster OR go with a smaller diameter brake booster.
    T
    Chrysler changed from a 4-bolt cast iron brake master cylinder to an aluminum 2-bolt brake master cylinder in 1978 (mid-year – I think, but it might have been the beginning of model year).
    Most everything is different, including the holes in the firewall between the 4-bolt (cast iron) and 2-bolt (aluminum) master cylinder versions.

    The differences between the (early) 76-77 (or early '78) and (late) '78 to 89 FMJ master cylinder's (and boosters) are:
    Firewall holes, Brake booster, Master cylinder, under-dash bracket and the manual brake firewall stiffener plate. This is going by memory so there might be more.

    The aluminum brake master cylinder is much preferred over the cast iron version, for several reasons.

    The holes in firewall or under-dash bracket are not hard to make (if needed).

    This is a late '78-89 under-dash bracket. There are 6 holes where it goes through the firewall. The rust colored is automatic and Black one is for a manual transmission.
    20190918_223458p.jpg
    20190918_223458r.jpg
    Same picture turned right side up. The yellow "X" is the upper hole for 4-bolt cast iron master cylinder.

    The top and bottom bolt holes are for the brake booster.
    The middle bolt holes are for the 2-bolt aluminum brake master cylinder. There are no shared firewall bolt holes between manual or power brakes (with exception of the firewall stiffener plate).

    The '76-77 (or early version) the lower 2 bolt holes are shared with either the 4-bolt (cast iron) or with lower brake booster studs.


    I “believe” the power and manual brake master cylinders can be interchange – providing you have the studs and the rubber grommet that holds the pushrod in place.
    2074960 Ring.png
    The rubber grommet (Chrysler calls it a Ring) is a part somewhat hard to find, but I “believe” it is the same as what was used for the late '60's Muscle cars – so it should be available (somewhere). It is also used for power brake cars.


    I just purchased these parts from a '79 F-body to install into my '77 wagon (once I make a new pair of holes on firewall).
    20200407_162757r.jpg
    20200407_162803r.jpg
    2-bolt master cylinder firewall stiffener plate. You can see the lower brake booster cylinder holes are in the firewall but are covered by this plate.

    20200407_163016r.jpg
    Aluminum master cylinder (with push rod and boot in place).


    I believe a person can make a new stiffener plate if you have access to drill press, measuring tools, materials and a bit of patience.


    Unrelated, these are pictures of a '66-70 B-body manual brake stiffening plate.
    20200407_163140r.jpg
    20200407_163147r.jpg
    A bit different – but mostly the same.
    A person could also make their own stiffening late if converting to a 2-bolt aluminum master cylinder or could use a bolt in place bracket (which is another option you have).
    Annotation 2020-04-07 161710.png


    he power brakes on my '77 wagon is too strong – so I was considering leaving power brakes in place but replacing the brake booster from a K-car (which is a lot smaller and has less power assist). I have comments and pictures in quite a few posts about using a smaller brake booster (if that was something you are considering).
    BudW
     
  3. Jonnylightening

    Jonnylightening Member

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    Thanks alot buddy. I was debating the whole K car booster. Im building a street strip car so i was thinking weight savings by going manual brakes. If I was to buy the plate off Mancini what all else would I need to make it all work?
     
  4. BudW

    BudW Moderator Staff Member

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    The pushrod length is an FMJ only item. Without one, I would get an adjustable length pushrod (Mancini is good to work with).

    Get the aluminum master cylinder.
    If you can find a manual brake master cylinder (eBay or other) – get it – for it will have the pushrod already with it.
    I do see new/reman manual brake master cylinders for sale from time to time.

    Make a new firewall stiffening plate (if you can't find one).
    If making one, I can perform measurements from mine and provide to you.

    Drill new holes into firewall/dash bracket (if converting from a 4-bolt to 2-bolt master cylinder). The holes already exist if going back with cast iron.

    Reassemble.
    The brake lines will need a tad of massaging to get to work - but they will (if not forcing).


    The good news is if you don't have the power brake assist you are looking for (or lack thereof), then replace with a K-car booster – just as long as you didn't toss any of your old parts (from booster).


    Personally, I think it will be easier to convert to a K-car booster.

    My opinion for a “performance” car driven on the streets, a brake booster is a necessity. For a race only car, then no. The problem with driving a car on the streets is too much human error can occur (and not on your end). Also you want your brakes to be top notch for street driven cars.
    BudW
     
  5. Aspen500

    Aspen500 Well-Known Member

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    I can attest to manual brakes being sketchy. With the EBC Yellow Stuff pads I put in (and brand new calipers), my Aspen stops good now, except you need to put a lot of force on the pedal for quicker than normal stopping. A so called "panic" stop would probably need both feet on the pedal, at least in my old worn out knees case, lol. I had an '81 D150 that was the same way with manual brakes. More than once I was glad it was an automatic, and the pedal was wide enough for both feet.:eek: Still, both are better than my first car, a '70 Barracuda Gran Coupe. It had 4 wheel manual 10" drum brakes and dragging your feet would have slowed the car down faster I think.
     
  6. Mikes5thAve

    Mikes5thAve Well-Known Member

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    I was going to mention that the k-car parts used to be to most common parts to use for these swaps, like BudW mentioned above. Too bad a lot of that stuff has also dried up in recent years.
     
  7. Jonnylightening

    Jonnylightening Member

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    What all year K Cars will fit? I was either gunna order new from rockauto or the local u pull it
     
  8. BudW

    BudW Moderator Staff Member

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    For boosters – pretty much anything made in the '80's front wheel drive – but I would shy away from Omni/Horizon parts sense those were not really that much compatible with everything else Chrysler made front wheel drive wise.

    They made two different boosters: One is a double or tandem booster – primarily for turbo cars (but not exclusively) or the single booster (mostly for non-turbo cars, but, again, not exclusively). The tandem is longer but narrower. I think the shorter but slightly wider single version is what you want. It will provide slightly less power assist than the normal FMJ version will and will have a smaller package (not quite ½ smaller).

    The only thing about the K-car booster is it is metric – which is not a big deal. You will just need to purchase metric nuts for it and a couple of adapters for the brake linkage (see my earlier posts about it – which I probably will need to make a “sticky”.

    Also, for what ever reason, almost all of the brake boosters sold today do not have any paint on them. Spending a bit of time and get a good paint job will make the underhood look a lot better – especially long term (looking at a rusty booster . . .).

    www.RockAuto.com is selling reman boosters for about $50 (not including tax or shipping). I think you can get a used booster cheaper – but being brakes IS THE MOST IMPORTANT item on the car, don't save a penny to only lose a dollar down the road.
    Annotation 2020-04-08 125107.png

    These pictures are NOT to scale. I have measurements of them in a different thread.
    FMJ booster:
    BB 3700210 a.jpg
    BB 3700210 b.jpg

    K-car single booster:
    BB Cardone 5474100 a.jpg
    BB Cardone 5474100 b.jpg

    K-car tandem booster:
    BB Cardone 5473172 a.jpg
    BB Cardone 5473172 b.jpg


    My thoughts are to install either a K-car single booster in place of the original booster in my wagon to help with the overboost condition. That said, my plans are to install stroked big blocks into both the wagon and Fifth Ave, so installing the K-car tandem booster into both cars might be best sense they will be street driven cars and with the additional weight of the big block.

    I already have one Cardone tandem booster purchased and, again, somewhere in the forums there is a side by side pictures of it and an FMJ booster to see the size difference.
    BudW
     
  9. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    How about the proportioning valve if going from power brakes to manual -is it different. The power vs manual master cyl is different isn't it
     
  10. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    I question if any given year if the manual/power master cyl is different, the push rods. I'm going power to manual on my 79 Volare Premere wagon using junk yard parts. Thanks for the input, it helps a lot that you are on this subject
     
  11. Aspen500

    Aspen500 Well-Known Member

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    The proportioning valve is the same from power to manual. There are 4 different p/n's listed. One is for wagon, one for 2 door coupe/ 4 dr sedan, another for taxi and the 4th p/n is Police.
     
  12. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    Thanks Aspen
     
  13. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    OK, going to manual on my 79 Volare wagon. Can I just throw the booster, use the power brake master cyl and use 2 of the 4 holes in the firewall. I need 2 bolts cuz all the studs are on the booster. I need a push rod don't I
     
  14. Lightning II

    Lightning II Active Member

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    Most likely.
     
  15. Aspen500

    Aspen500 Well-Known Member

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    Yes, you will need a manual brake pushrod. The parts catalog lists two different p/n masters, one for power, one for manual. I believe it's because the manual is shown with a pushrod and dust boot and the power master obviously doesn't. From what I can find, and PLEASE correct me if anyone knows different, the pistons are the same size for both. Aftermarket only lists one p/n for masters.
     
  16. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    OK Aspen, I can get a manual master at j. yard and if it isn't good I'll buy new/rebuilt cuz I need the pushrod. Thas my plan. Thanks for the tips. My stiffener plate will work with holes in it already. I'll get a couple 5/16 gr 8 bolts the right length to hold the master on.
     
  17. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    I just looked at your Aspen brake master cyl. I'll get the stiffener p[late at the j. yard also
     
  18. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    I can get a new manual brake pushrod/boot on ebay for 22 bucks with shipping
     
  19. Aspen500

    Aspen500 Well-Known Member

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  20. ZieglerSpeed

    ZieglerSpeed Well-Known Member

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    OK, sounds good. I'm in a little town where our NAPA is 10 percent cheaper than normal as a favor to the community and they are really good people