Engine upgrade question ...

Discussion in 'The Garage' started by mydnyte, Sep 23, 2004.

  1. mydnyte

    mydnyte Registered Member

    Sep 20, 2004
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    Hillsboro, Oregon
    I have an aging SB400 in my K20. It is fine for now as the bottom end is still solid and the top end was recently re-built (Exhaust opened up and RV cam included).

    My question is what would a guy have to do to a SB400 to get around 400HP at the wheels? I intend to go with a set of headers for certain and since there is no cats on this year exhaust flow wont be a problem. I would like to use a quadra jet carb due to the position of the floats but dont look forward to rebuilding one so another carb/intake is likely.

    Any sugestions and/or links would be helpful.


    Clifford /forums/images/graemlins/truck.gif
  2. Thunder

    Thunder 3/4 ton status

    Jul 20, 2000
    Likes Received:
    Northeast Nevada
    You would have to do a little building on that aging stocker to get 400 RWHP.
    You will need a few little things like.......
    Better heads
    higher compression ratio
    forged pistons,rods, crank.
    Hotter cam.
    Good intake,headers,exhaust
    Plus all the other fancy doo-dads one needs for a high performance engine.
  3. smprider112

    smprider112 1/2 ton status

    May 1, 2004
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    sometimes HP is better left to cars....as generally with a smaller motor pushing higher HP numbers that power is ussually up high....yer better off with a truck to build it for more low end torque /forums/images/graemlins/thumb.gif but thats just my oppinion...and you will need heads, cam, intake, etc.. as stated prior /forums/images/graemlins/thumb.gif
  4. Topdown

    Topdown 1/2 ton status

    Nov 26, 2002
    Likes Received:
    Vancouver, Washington, U.S.A
    as a member of the 400/400 club I can tell you exactly what you need but I can also tell you that if your planning on putting it in your lifted truck and you value your life you might want to think again.

    Trick flow heads - get the CNC machined ones 64cc chambers, go with big valves and big valve springs - 2.02 or 2.05 exhaust
    Comp Cams extreme energy cam... I had the XE268 but there is a 284 and I think another one bigger, get one of those
    1.6 or 1.7 ratio roller-rockers - lets make that cam REALLY big - plus the full roller rockers will let loose some high-end HP due to lowering friction.
    Dont forget to use Chromoly push-rods otherwise they will flex/bend and at 5000rpm a bending push-rod is death.
    If you want, you can go to a roller-cam instead of a normal cam, that will open up a whole new realm of opportunity.
    Use a real good forged flat-top piston - not aluminum, not hypereutectic... forged. when your pushing 5000+ RPM the aluminum and hyper pistons will deflect and bend under the stress and that will make them come apart and thats bad.
    you will want a forged crank - probably not absolutely needed but I prefer the strength of the forged at those RPM numbers.
    I prefer Edelbrock intakes... Air-Gap
    Fuel injection - better power with FI but if you have to carb it and still plan on wheeling with it, get a 750CFM Q-jet and have it tuned/jetted just right, there is a lot to gain/lose in the wrong or bad tuned carb.

    Ultimately keep in mind that you will lose between 15 - 25% of your HP/Torque through your transmission... so, you have to build an engine with that much more in it to get 400bhp. Also keep in mind that going for HP usually means that the HP comes on later in the RPM band... so gear your truck accordingly.

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