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  1. #1
    Join Date
    Dec 2011
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    Rugby,West Midlands.
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    60
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    609

    What type of exhaust manifold bolts

    I have taken off the n/s exhaust side pipe in order to get a crack welded up where the collector merges with the large main section. Before I drifted the four pipes off the manifold to separate the system, I checked to make sure all the exhaust manifold bolts were tight in the heads, and they were all a bit loose. I then noticed none of them had any form of anti-vibration washer, which I thought was strange. So I took one out to see if it was long enough to take a spring washer, and the threaded portion is only ¾” long, which has to go through the ¼” thick manifold plate. So I won’t to buy some longer bolts, but I am not sure what type of thread they are.

    My current flanged bolts are plated, 1” long in total, threaded portion is ¾” long ( see attached snap)



    Thread diameter is 0.375”, which is 3/8”, with 16 TPI, and according to my Zeus tables that seems to indicate that are 3/8” UNC bolts….. Am I right?

    If it helps, my SBC is fitted with Patriot heads, which I am hoping take the same bolts as a standard SBC head.

    Should I get stainless steel bolts, to make sure they don’t seize up and should I use spring washers on re-assembly.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  2. #2
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
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    55
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    9,511
    Not had any type of anti-vibration washer or gasket fitted in years due to the bolts always going loose and the exhaust gasket blowing. Just use high temp silicon now and in 10 or so years never had a bolt come loose or had either side blow. The only way to go in my opinion. The bolts you have shown are the ones I use also.
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  3. #3
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
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    61
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    9,916
    3/82 UNC is correct for a SBC.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
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  4. #4
    Join Date
    Feb 2011
    Location
    Northampton
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    41
    Posts
    4,010
    Quote Originally Posted by kdavies3 View Post
    3/82 UNC is correct for a SBC.
    Crikey that's small, Kev
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  5. #5
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
    Age
    61
    Posts
    9,916
    Doh! fecking caps lock.
    3/8" UNC.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
    Contemporary CCX 3-4028, 445ci Big Block FORD FE,TKO 600, Old School IVA'd and SOLD
    Dax De Dion LS2 and T56 IVA'd June '17 SOLD
    1965 Ford Mustang 289 Convertible FOR SALE
    In build- Hawk 289 Sebring

  6. #6
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    609
    Not had any type of anti-vibration washer or gasket fitted in years due to the bolts always going loose
    Thats why i was thinking of using spring washers.

    Just use high temp silicon now and in 10 or so years never had a bolt come loose or had either side blow.
    Thats between head and manifold flange i gather, i want to find a silicone flexible sealer which will withstand temps between 800-1200 degrees,for when i re-assemble the four pipes back into the manifold,as it was blowing slightly before ,so it dont go hard ,crack and fall out.
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

  7. #7
    Join Date
    Dec 2011
    Location
    Rugby,West Midlands.
    Age
    60
    Posts
    609
    Quote Originally Posted by kdavies3 View Post
    Doh! fecking caps lock.
    3/8" UNC.
    Thanks, i now know what sort of bolts they are
    Paul.

    AK Huddart Chevy 383 Stroker, BMW Royal Grey Metal Metallic , 5 speed Jaguar Getrag , Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel , 460 Ibs/ft torque, and luvin it !

    " We dont stop playing because we grow old, we grow old because we stop playing" - George Bernard Shaw.

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