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Thread: hot 4k build help

  1. #1
    Forum Member 1st year Apprentice
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    Default hot 4k build help

    hi guys , i need help with carby sizing for my 4k ..
    it is a 4k 60 over size , very ported, bigger valves
    cam is pretty big the specs are
    duration :294/298 valve lift : 415 /426
    power range is from 2900-8700rpm lol
    i thought i might get away with a 32/36 or twin 40s with 33chokes
    any info would be good
    cheers

  2. #2
    Junior Member Carport Converter Billzilla's Avatar
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    Default Re: hot 4k build help

    That's heading towards what I used to run in the racing car. You'll be better off with 45 DCOE Webers running 36mm chokes.
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  3. #3
    Junior Member Grease Monkey
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    Default Re: hot 4k build help

    what model head are you running
    1985 RT142, 1GGTE,.now with t67-25g
    2009 Ford Fiesta LX
    1970 Ford Cortina MK2 440

  4. #4
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: hot 4k build help

    remember to machine down the rocker towers.
    ITB injection will be leagues ahead. 7KE lower manifold would be ideal.
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  5. #5
    C'mon, Touch My Grease Monkey SLO-030's Avatar
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    Default Re: hot 4k build help

    Mmmmmm, ITB equipped 4K.
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  6. #6
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: hot 4k build help

    Quote Originally Posted by oldcorollas View Post
    remember to machine down the rocker towers.
    ITB injection will be leagues ahead. 7KE lower manifold would be ideal.
    machine down the rocker towers? whats that about?

  7. #7
    Zub Zub Domestic Engineer Gavatron's Avatar
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    Default Re: hot 4k build help

    Fixing the rocker/valvetrain geometry.
    || 91 MX83 Cressida Grande 1JZGTE - Daily || 84 MA61 Supra 2JZGE - Track ||

  8. #8
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: hot 4k build help

    yeah ok, sounds nasty

  9. #9
    C'mon, Touch My Grease Monkey SLO-030's Avatar
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    Default Re: hot 4k build help

    Quote Originally Posted by oldcorollas View Post
    remember to machine down the rocker towers.
    ITB injection will be leagues ahead. 7KE lower manifold would be ideal.

    Interesting, How much do you have to take off the rocker towers to make this effective?
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  10. #10
    I even do the dishes as Domestic Engineer Rodger's Avatar
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    Default Re: hot 4k build help

    My choice would be 40mm with #34 chokes, but I am Old School.

    The Weber would be an under performer and limit you top end power.

    Buy a dual sidedraught Redline Manifold as a starting point. Then you can go carbs or twin Dual Barrel ITBs with the same bolt pattern.

    A totally set up ready to bolt on and run dual 40mm Solex for that manifold combination is around $900 including cable and linkage.

    EFI is better for overall drivability and gives the ability to control AFR better. There is always the debate over outright power outputs between this and carbs. Price depends on cost of ITBs, levers and ECU chosen. Again I would pick an ITB that has tapered bores and throttle plate size of 40mm or the 43mm as per the second link below.

    http://www.efihardware.com/products/...hrottle-bodies

    http://www.efihardware.com/products/...s-45mm-to-50mm

    Either combination aims to give as much air speed as possible and balance this with outright total air capacity, considering that there will not be much drivability in that engine combination anyway.

    Both carbs and ITBs can use the same cable and balance bar linkage that would be added onto the manifold.

    Do you have a light flywheel?

    Regards

    Rodger

  11. #11
    Forum Member 1st year Apprentice
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    Default Re: hot 4k build help

    yer i have a slightly lighter flywheel , i like the idea of itbs but the sound of 40-45 is very nice and im trying too keep the car old school but in saying that a injection setup with a megasquit or haltech would be epic for tuning willl 20v itb from a silver top fit to a older toyota manifold with small modification????

  12. #12
    I even do the dishes as Domestic Engineer Rodger's Avatar
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    Default Re: hot 4k build help

    Small mod I do not know. They will not fit on the original k manifold without a lot of cut and shut alloy welding. The 20v ITBs do not have the same bolt pattern as the sidedraught so cannot be easily adapted to the Redline manifold either.

    Regards

    Rodger

  13. #13
    Forum Member 1st year Apprentice
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    Default Re: hot 4k build help

    ok well my mate is an engineer and alloy welding machine lol so maybe he could do something for me , what do efi 7k come out in unless anyone wants to sell me some twins lol

  14. #14
    I even do the dishes as Domestic Engineer Rodger's Avatar
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    Default Re: hot 4k build help

    Ok

    Now we are down to asking. What do you want to do with this motor?
    An adapted efi from a 7k will achieve only so much and will be limited by the single throttle body size effectively like putting the Weber 32/36 on.

    Regards

    Rodger

  15. #15
    I even do the dishes as Domestic Engineer Rodger's Avatar
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    Default Re: hot 4k build help

    Machining the rocker posts solves an issue that puts the rocker on such an angle at full lift that the push rod fouls the rocker at the adjustment ball/screw and the head could drop off the side of the valve. It brings the rotation angles about the shaft back to the OEM position.
    Amount is determined by a combination of cam lift and how much was removed from the head when raising compression. Once the motor is assembled then it can be checked as the cam is dialed in and valve clearances checked.

    If enough is taken off, the head bolts need to be checked to see if they bottom out, then packed up with a washer or shortened or head studs get used.

    Regards

    Rodger

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