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What engine for my mini stock?

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  • What engine for my mini stock?

    I have decided to move up a class with my race car after this year. My car is a 1989 240sx with a later DOHC engine. On 65 series street tires I am not too far behind the slower mini stocks with unlimited camber and slicks.
    The rules as regards to engines are much more open if I move up, and I am wondering if I should stick with my KA24de, or is there something else out there that would be a better option?
    We run on mostly 1/4 mile banked ovals, and torque is pretty important. My engine at 2.4 liters is too big but other tracks are allowing it and my track will make an exception for me.

    Engine rules are below and I welcome any thoughts....


    7. ENGINES CARBURETED ENGINES
    A. Four cylinder engines.
    B. Must be same manufacturer as the body, i.e. Toyota-to-Toyota, Honda to Honda.
    C. Maximum displacement 2300 cubic centimeters.
    D. DOHC allowed (see weight section).
    E. Maximum .040 inch overbore.
    F. Balancing of engines and lightening of flywheel is allowed.
    G. Power to electric pumps must be interrupted when the ignition is turned off. A Hobbs type switch is required.
    H. Any reground camshaft allowed.
    I. 11.0 to 1 max. compression ratio.
    J. No stroking, de-stroking or de-tuning of engines allowed.
    K. No mixing of 2.3 and 2.5 Ford engine parts.
    HEADS, CARBURETOR AND INTAKE MANIFOLD
    A. Cylinder head may be surface machined any amount. No porting, polishing or altering allowed.
    B. Stock single carburetor.
    C. Optional carburetors in place of O.E.M. are the Holley 5200 or equivalent and the Holley 350cfm.
    D. A 1-ΒΌ inch spacer/adapter maximum . Bolt on assembly only.
    E. Stock O.E.M. single plane manifold. No fuel injection air plenum manifolds. No grinding of intake manifold allowed.
    F. No turbo chargers. No superchargers.
    G. Air filter with metal lid is mandatory.
    H. One air duct allowed.
    NOTE: IF AN EXISTING CARBURETED CAR, THAT WAS ORIGINALLY FUEL INJECTED, WISHES TO RETROFIT BACK TO THE STOCK FUEL INJECTION SYSTEM IT WILL BE REQUIRED TO CONFORM TO ALL FUEL INJECTION RULES.
    FUEL INJECTED ENGINES
    A. Four cylinder SOHC or DOHC engines.
    B. Maximum displacement 2300 cubic centimeters.
    C. Maximum .040 inch overbore.
    D. Must be same manufacturer as the body (i.e. Toyota to Toyota, Honda to Honda).
    E. Engine must remain stock (i.e. Stock internals, stock cam/s, stock cam pulleys). Untouched factory engines or stock rebuilds only.
    F. Fuel injection system is to remain stock. Intake manifold, throttle body, mass air flow sensor, injectors, wiring harness and all other components related to fuel injection system must be stock for engine used.
    G. Stock computer for engine used must be used. Chips, removal of factory rev limiter and retunes of factory ECU allowed. No stand alone systems (i.e. Mega Squirt, Motec).
    H. Power to electric fuel pumps must be interrupted when the ignition is turned off. A Hobbs type switch is required.
    I. Aftermarket air cleaner and intake tube allowed. Must use factory mass air sensor.
    J. One air duct allowed.



    5. WEIGHT
    A. Weight/engine size must be painted on hood.
    B. Cars scaled with driver after race.
    C. Carbureted cars to weigh one lb. per cubic centimeter (engine size).
    D. SOHC fuel injected cars to weigh one lb. per cubic centimeter (engine size).
    E. DOHC engines add 75 lbs. to total weight (carbureted or fuel injected).
    F. Left side rule is 55% with driver belted in.

    Below is me on my way to second in the A main on Saturday. Its a fun class but I`m getting tired of the crashfest.


    http://www.youtube.com/watch?v=8DRDMCIGL0U

  • #2
    Most "mini-stock" classes were originally designed around the Ford 2.3 Lima engine so that's where the 2.3 comes from. Nissan doesn't have much between 2.0 and 2.4 over the years other than some funky twin-plug engines back in the early eighties. They were Z series motors and can be found in the old 200sx with a grand total of 103HP!

    If they're not complaining about the extra 100cc I'd stay with the KA24DE. With the rules you've listed it looks like you could run an aftermarket cold air intake and a tuned ECU but I didn't see any rules conerning exhaust so I can't say about that. Don Nimi at PDM-racing.com claims about 170rwhp on a DE with CAI, header, cat-back, his ECU tuning and 100 octane gas.
    Don Johnson (really!)
    Just so you know.

    Comment


    • #3
      Sorry, neglected the exhaust rules. Headers allowed, but 95 db so a straight through muffler of some kind.
      If you watched the video, the red and yellow sentra is the only car faster than mine other than the other 240(that I helped build this winter and turned out to be over a tenth faster than mine but I'm not bitter)
      The Sentra is an SER and it pulls me on the straights like I'm tied to a safe.

      Comment


      • #4
        Originally posted by bearmtnmartin View Post
        Sorry, neglected the exhaust rules. Headers allowed, but 95 db so a straight through muffler of some kind.
        If you watched the video, the red and yellow sentra is the only car faster than mine other than the other 240(that I helped build this winter and turned out to be over a tenth faster than mine but I'm not bitter)
        The Sentra is an SER and it pulls me on the straights like I'm tied to a safe.
        The Sentra SER has an SR20DE but the older Sentras are also quite a bit lighter than the 240sx and that's why he's pulling you. I'm not a Sentra expert but in the early 90's they came with both low-port and high-port versions and I think the high port versions were better. They were still selling the old B13 Sentras in Mexico a few years ago.
        Last edited by djsilver; 05-28-2012, 07:01 PM. Reason: B13 Sentras- not an expert!
        Don Johnson (really!)
        Just so you know.

        Comment


        • #5
          yeah the only engine I see as an option other than the KA is an SR, it may be worth the 400lb weight reduction but I'd say a sr20DE at 11:1 still wont make piles of torque, but It would be legal for your class as far as i can tell. the ringer might be a SR20VE but It'd be hard to meet the manifold requirements in a RWD vehicle...


          how close are you to the 1lb/CC limit as of now (and are you required 2475lb or 2375lb since that is theoretical limit?)
          I am SKULLWORKS

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          • #6
            Right now I am 2341 pounds. But I can replace a lot of tin with plastic for this class and I may go with a 5 star body so I will almost certainly have to add weight, even after I add some tubes to my cage.

            Comment


            • #7
              So I guess I am staying with the KA.

              Thanks for the help!

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