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  1. #1
    Join Date
    Mar 2020
    Location
    Norfolk
    Posts
    38

    SBC - head bolt cleaning tap

    Hi there,
    I'm replacing my cylinder heads on my 350 SBC and want to clean the thread for the head bolts.

    I understand that the thread is 7/16"-14

    Any idea where I could get one of these in the UK (or something similar) https://www.summitracing.com/parts/arp-911-0004

    I understand these 'cleaning' taps are less harsh them a proper tap.

    Or perhaps someone could lend me one?

    Any help appreciated - bear in mind - I'm a muppet.

    Phil

  2. #2
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
    Age
    63
    Posts
    10,280
    I'm sure you'll find one on Ebay.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
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  3. #3
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,737
    "Thread chaser" is what you're looking for and they seem to be awfully hard to find in the UK in imperial sizes, now. If you don't want to use a 7/16 UNC tap, though, you can take a bolt and cut four lengthwise grooves into the threads (see pictures of a real thread chaser here: https://mechanicalmalarkey.com/2018/...he-difference/) - it'll wear out quicker than a chaser and isn't as hard, but it'll clean out rust & gunk with no risk to the threads themselves.

    If it binds, then use a tap instead, because there's a galled thread that needs re-cutting.

    I've always tended to use a tap personally, though I realise it isn't ideal
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  4. #4
    Join Date
    Oct 2018
    Location
    Shipston-On-Stour
    Posts
    567
    I always use a 7/16 UNC tap. Surprising how much crap can come out!
    Dax with 1964 Dual Quad 427 and Toploader box

  5. #5
    Join Date
    Nov 2006
    Location
    Shropshire/Wales Border
    Age
    50
    Posts
    6,075
    As above, just run a tap down the threads. Good practice for any thread in your rebuild.
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

  6. #6
    Join Date
    Mar 2020
    Location
    Norfolk
    Posts
    38
    Well I found the ARP tap in the UK https://shop.arrowprecision.com/7-16...aning-tap.html - but £60!!! I think I'll just get a regular one

  7. #7
    Join Date
    Mar 2007
    Location
    Maldon Essex
    Posts
    522
    I have never had a problem using a normal tap for these jobs, just make sure you get it started properly and use some oil. I have always used a plug tap or No3 tap as its not for starting the thread cutting process so will be far less able to chew up your existing thread and just follow it.

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