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Thread: Larger bore bolt in master cylinder for Spirit R/T?

  1. #1
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    Larger bore bolt in master cylinder for Spirit R/T?

    Got the new Wilwood big brake set up installed on the front of my Spirit R/T and even after repeated bleeding sessions I still have a spongy pedal. I was wondering if there is a factory style larger bore master cylinder that would be somewhat of a bolt in. Thanks in advance

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    You could use a D150 MC, but you would need adapter fittings for the different size flare on the D150 MC. Do you know the difference in volume between the calipers you have on there now and what was on there before?

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by cordes View Post
    You could use a D150 MC, but you would need adapter fittings for the different size flare on the D150 MC. Do you know the difference in volume between the calipers you have on there now and what was on there before?
    No sir. I don't know the difference in volume between the 2 set ups. I'm afraid I'm a fish out of water with this tech

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Do you have a link to the calipers you're now using? I did some math on this a while back and the calipers on the Viper have a lot more volume than what our 60mm units do. I'm sure Reaper will be along shortly to help with this, but I recall him saying the way fixed calipers work, they don't need as much MC per unit of vol.

    The calipers you're using now are fixed units, right?

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Cordes knows me all too well! LOL

    So, he is right on all counts.

    I have not done the math, personally, but I can relay what I was told by Mike Stimac. He was running Viper 4-pot calipers up front and factory '88 Shelby Z brakes out back (yeah, not even updated ones!) with a stock 24mm master cylinder and a Wilwood proportioning valve if memory serves.

    Yes, fixed calipers typically require less volume of fluid to actuate the pads because you are only moving the pistons and pads, not the entire caliper, and the distance needed to travel is less (all in theory, of course).

    A larger MC will make the pedal harder for sure, but it might be at the cost of modulation.

    One last thing: I have found recently that supplied copper washers aren't thick enough for the banjo fittings in some instances (this is all reman stock stuff, so might not be applicable here). This causes the banjo to bottom out before a seal is achieved at the fitting. Make sure you aren't having that sort of issue, too.

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by Reaper1 View Post
    One last thing: I have found recently that supplied copper washers aren't thick enough for the banjo fittings in some instances (this is all reman stock stuff, so might not be applicable here). This causes the banjo to bottom out before a seal is achieved at the fitting. Make sure you aren't having that sort of issue, too.
    Do you have the proper dimensions of the copper washers?
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by chromguy View Post
    Do you have the proper dimensions of the copper washers?
    No, sorry. I ended up using old factory ones. Not exactly "best practice", but it worked!

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    http://minimopar.knizefamily.net/per...es.html#master

    I recall the D150 being an upgrade w/ stock brakes. I believe that Chris Still's Daytona has them.

    Might want to let TCE weigh in.

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    Super Moderator Turbo Mopar Staff 135sohc's Avatar
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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by Reaper1 View Post
    No, sorry. I ended up using old factory ones. Not exactly "best practice", but it worked!
    Heat them until glowing with a propane torch and let them cool. Reanneal the copper and good to go.
    1994 Shadow Sedan. 2.2 N/A, A568 382,000 miles. (In the family since new).
    1987 Shelby CSX #418. Long term rebuild and restore.

  10. #10

    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by Wastelands Warrior View Post
    Got the new Wilwood big brake set up installed on the front of my Spirit R/T and even after repeated bleeding sessions I still have a spongy pedal. I was wondering if there is a factory style larger bore master cylinder that would be somewhat of a bolt in. Thanks in advance
    When I re-configured the brakes on my Laser, I encountered the same problem. after a lot of digging on the Wilwood web site I discovered they offer a direct Mopar style replacement Masters in larger bore sizes.
    Also, Jegs has Mopar style Master cylinders in three or four larger sizes. (bolt on replacements)

    I had to calculate the area, or should I say volume ratio between the stock master cyl. and stock calipers and try to match that ratio with the new set-up and find a new larger master cyl. to achieve the same approximate ratio. If that makes any sense.

    I discovered I could bump the pedal feel and pressure substantially by changing the master cyl. diam. by 1/32. I tried three masters till I got it right.
    best 1/8 ET-6.2 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.73 sec. @144.26mph. 8 valve NO NITROUS!!

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by 135sohc View Post
    Heat them until glowing with a propane torch and let them cool. Reanneal the copper and good to go.
    Cool...ah sorry HOT
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

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    Super Moderator Turbo Mopar Staff 135sohc's Avatar
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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Pretty sure it was someone here who mentioned doing it. Makes sense and you know the washer will be the right size. I have changed plenty of brake hoses and a few calipers over the years and the replacement washers everything comes with are always a bigger OD and noticeably thinner. Some cheap generic crap from a rebuilders supply catalog that is 'close enough' to look alright but not in spec.
    1994 Shadow Sedan. 2.2 N/A, A568 382,000 miles. (In the family since new).
    1987 Shelby CSX #418. Long term rebuild and restore.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    I forget the correct thickness, but last I checked, they were available off of Rockauto.com for cheap. One could buy 20 of them and be set for a while for a relatively small amount of money.

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by cordes View Post
    I forget the correct thickness, but last I checked, they were available off of Rockauto.com for cheap. One could buy 20 of them and be set for a while for a relatively small amount of money.
    LOL, That is exactly what I did a few years ago.
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

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    Re: Larger bore bolt in master cylinder for Spirit R/T?

    Quote Originally Posted by 135sohc View Post
    Heat them until glowing with a propane torch and let them cool. Reanneal the copper and good to go.
    i do this myself as the original washers are usually far better than the thin aftermarket replacement.

    if i do get a pack of thick ones randomly with a reman caliper then i use them but i keep the originals.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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