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  1. #1
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    What Size // Threads on 2003 corvette m/c

    Please post up if you know.. I've searched the website and other places with no luck. Does anyone know what size is the aft port of the M/C ..It is metric and 1.5 tpi. I thought it was 12mm x 1.5 but cannot find and adapter or tubing nut need 3/16 line. The master cylinderr is AC Delco 19288642



    Thanks
    BobH


  2. #2
    Join Date
    Aug 2007
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    282
    They are an odd ball size. The only way I found them is buying them from a corvette salvage yard. Just tell them what you want. They will just cut the line and save the nut. You may have to drill out the nut slightly to get the 3/16" line thru. Or you could order the line from a dealership just to get the nut. I'm running a C5 master and booster on 68 C10 and it works great.

  3. #3
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    Apr 2009
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    I'm going through this right now too. The port closest to the booster is M12x1.5 and is actually for the front brakes (kind of counter-intuitive). The port towards the radiator is M12x1.0 and is for the rear brakes. They're both ISO bubble flares.

    M12x1.0 ISO male to 3/8-24 inverted female adapters are readily available: https://shop.advanceautoparts.com/p/...33c/22190110-P

    I cannot find M12x1.5 ISO male to 3/8-24 inverted female adapters anywhere. If anyone has a source, let us know!

    There some good reference info in this post as well: https://www.pro-touring.com/threads/...-line-fittings

    The stock fittings are designed for 6 mm brake tube, which can be made to work with with 1/4" tube. I'd prefer to go with all 3/16" brake line though.
    - Ryan

  4. #4
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    Jun 2014
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    Thanks for the responses.. I didn't know about the fwd port was for the rear brakes, Thanks. The aft port is killing me ..it is 12mm x 1.5 bubble fitting but I have yet to find a source . Not sure if I could even find a Corvette in the yards around here. If I don't locate one soon I guess its another M/C for me. I cant believe no one manufactures the fitting/ adapter
    Thanks
    BobH

  5. #5
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    What I ended up doing yesterday is ording an Edelmann 262400 adapter - it's M12x1.5 bubble male to 7/16-24 female inverted flare. From there I plan on using a 7/16-24 tube nut on 3/16 line using an Edelmann 121034 tube nut. This tube nut is kind of special because it uses the thread size for 1/4" brake line (7/16-24) but the "hole" in the fitting is sized for 3/16" line. I got the adapter and tube nut on rockauto - about $3 total + $3 shipping.

    I have to give this guy some credit for the idea - it seemed to work out for him: http://www.vettemod.com/forum/showthread.php?t=7030 (post #7)
    - Ryan

  6. #6
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    Quote Originally Posted by stab6902 View Post
    What I ended up doing yesterday is ording an Edelmann 262400 adapter - it's M12x1.5 bubble male to 7/16-24 female inverted flare. From there I plan on using a 7/16-24 tube nut on 3/16 line using an Edelmann 121034 tube nut. This tube nut is kind of special because it uses the thread size for 1/4" brake line (7/16-24) but the "hole" in the fitting is sized for 3/16" line. I got the adapter and tube nut on rockauto - about $3 total + $3 shipping.

    I have to give this guy some credit for the idea - it seemed to work out for him: http://www.vettemod.com/forum/showthread.php?t=7030 (post #7)
    Good idea...I did see that adapter and didn't even think of the 1/4 with 3/16 tube

    I will give it a shot... I do however have a back up plan on the way.. 1 1/8 bore master cylinder from a 1999 chevy truck

    Thanks Again,

    BobH

  7. #7
    Join Date
    Aug 2007
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    282
    Just looked at my setup again.
    Rear port C5 master 3/16" line to the front brakes. Used the "stock" C5 nut.
    Front port 1/4" line to the Willwood adjustable prop valve to the rear brakes. Used the C5 nut. Adapter to adapt the 1/4" line to the Willwood prop valve.
    I mounted the prop valve right under the brake master so the there is one short 1/4" U bend from the master to the prop valve for the rear brakes.
    Don't know if this helps but GM has tendency to use similar parts across all of their car lines. I'm a big salvage yard diver so it could be that the master cylinder nuts across product lines are the same?

  8. #8
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    1970 Camaro/DSE build


    Are you driver enough? Maybe....come on blue!
    https://www.pro-touring.com/threads/...71#post1147371

  9. #9
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    Those DSE tube nuts would work for one port, but not the other since it's M12x1.5.
    - Ryan