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Thread: 7M Head Cross Section

  1. #1
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default 7M Head Cross Section

    i decided to give my huge new drop saw "chomp" a challenge and do a cross section of a spare head i had, in prepartion to port another one for my high rpm NA build.









    through valve line:




    (intake)






    (exhaust)


    There is no substitute for PUBIC inches

    Never late in an x8

  2. #2
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    back of this section:




    along port divider:


    (intake)




    (exhaust)




    valve bowl with valve. i have relieved some areas to make it easier to see:


    (intake)


    (exhaust)



    hopefully these photos can be of use to others, i have more if there is something you want to see more specifically or want any measurements. it is intersting to notice how the ports are not necessarily symmetrical with the valves, and it seems each cylinder is different so caution is still required near water jackets.
    There is no substitute for PUBIC inches

    Never late in an x8

  3. #3
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 7M Head Cross Section

    awesome

    drop saw ftw!
    "I'm a Teaspoon, not a mechanic"
    "There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)

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  4. #4
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    haha yeah its "adequate" twin belt drive, motor draws 16.8amps. i had to rewire the shed and run 6mm cable to the main switch to run the damn thing without blowing fuses lol. now it cuts through the big traffic light poles in one cut..... check out the stand
    There is no substitute for PUBIC inches

    Never late in an x8

  5. #5
    Corona loving Grease Monkey TTMX83's Avatar
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    Default Re: 7M Head Cross Section

    I like the use of a beer for counter balance
    2010 KDJ150 Prado

  6. #6
    Olde mechanic Carport Converter oldeskewltoy's Avatar
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    Default Re: 7M Head Cross Section

    sorry... I don't have a sharp drop saw comment.........


    What I do see is similar flaws to a 4AG big port - rough casting, and poor matching @ the valve seat. Small port 4AG have better guide boss design, and better placement of the valve seat in the head
    Information is POWER... learn the facts!!

  7. #7
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    valve guide boss is the biggest restriction by far, drops from 30mm at port entrance to 20mm @ guide boss and around 28mm @ valve bowl.

    with some short side radius reshaping and losing a LOT of the guide and boss i should be able to achieve 30mm all the way through.

    only decision now is what to do with the valves, i see no point in going the usual route of 1mm O/S valves on stock seats as i cant see how it will give any improvement in flow. weighing up the cost of 2mm O/S seats and valves all round but with 24 of them it gets expensive....
    There is no substitute for PUBIC inches

    Never late in an x8

  8. #8
    Your mum is a Conversion King TERRA Operative's Avatar
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  9. #9
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    cool thanks! thats something like what i had in mind, with less of a point on the boss, probably 30% smaller than the smallport example..... basically leave just enough of it to support the guide properly.

    to get 30mm through the entire port with an SSR similar to the smallport inlet gives me about 2/3 of the original guide length, is this enough?
    motor is a race only, high rpm 7m-ge.


    interesting how much earlier they divide the ports in the pics you linked, i have a bigport in the shed waiting to go in a mini, i will have a look down the ports and see what they are like for comparison...
    There is no substitute for PUBIC inches

    Never late in an x8

  10. #10
    Olde mechanic Carport Converter oldeskewltoy's Avatar
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    Default Re: 7M Head Cross Section

    Any views down the ports? Any of the ports from the chambers view?
    Information is POWER... learn the facts!!

  11. #11
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    sorry for the delay getting pics, been absolutely flat out!

    full port view:


    cutaway port views:




    chamber views:








    and here is what i am talking about with the restriction of the guide boss:




    havent made a start on porting yet, still procrastinating about what to do with the valves. destroked bottom end is coming along well though so i am slowly making progress
    There is no substitute for PUBIC inches

    Never late in an x8

  12. #12
    Teh Massif Dong Carport Converter BlackSupra's Avatar
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    Default Re: 7M Head Cross Section

    Any chance you dropped the saw through the middle of one of the lower hex plugs on the top of the head, between the spark plugs on 5&6, 3&4 and 1&2?

  13. #13
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    hey mate i did a cut thru that, check out the first pic in the second post it shows the thread it screws into.... i think i threw the half piece of plug out ill have a dig around see if i can find it
    There is no substitute for PUBIC inches

    Never late in an x8

  14. #14
    Teh Massif Dong Carport Converter BlackSupra's Avatar
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    Default Re: 7M Head Cross Section

    That image appears to be through the higher hex plug as it is level with the top of the head.

    The 4th image down in the original post shows the lower plug at a height below the top of the head. That's the one i was interested in.

  15. #15
    Cressidaspert Carport Converter andrew_mx83's Avatar
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    Default Re: 7M Head Cross Section

    are you talking about the 14mm ones that hold the big black plate over the plug valley in?
    There is no substitute for PUBIC inches

    Never late in an x8

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