Yet another H/P *estimate* request.

Discussion in 'Classic Mustang Specific Tech' started by Spanish Dave, Mar 12, 2004.


  1. Spanish Dave

    Spanish Dave Member

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    Hi there
    I was wondering if anyone could give a rough idea of the power output of the engine I have ... (it isn't really easy to get it dyno-ed here in Spain).
    It is a 289 block bored 30 over with Keith Black flat-top pistons, the heads are 351W from 1970 with stock valve sizes and I worked the compression out to be 9.6:1. The cam is a comp cams 280h with .512 gross valve lift for int & exhaust and 230 duration at .050 at both intake and exhaust .. lobe separation 110. New comp cams lifters, valve springs and roller tip rockers with 1.6 ratio. The carb is a holley 650 with vac secondaries on a weiand stealth intake manifold. The headers are Try-Y or similar with 3 inch collectors leading to a 2.5 inch dual exhaust system with a H-pipe. Most other stuff is stock and the car has a 4 speed top loader with Hurst comp plus shifter.
    Nearly forgot .... GT350 side stripes ... must be worth at least 25hp. :D
    Sorry to have to post this, but I have no idea how to *guesstimate* HP.
    #1
  2. 68coupe408

    68coupe408 Member

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    I guess almost 1 hp per inch, so roughly 280-290ish @ the motor.
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  3. Ozsum67

    Ozsum67 Too much thin air Founding Member

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    There really is no way to get close without a dyno. You can add up HP estimates for various componets, but the tune of the engine has to come into play. In the end, it is only a guess and probably a very poor one at that.
    #3
  4. Spanish Dave

    Spanish Dave Member

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    Thanks for the replies
    Ozsum67 ... I do realise that there a lot of factors effecting hp, but as I said I have no idea where I could find anyone with a dyno round here in Spain ... they are not so long out of donkeys here, never mind horsepower :p
    It is not an exact estimate, just a rough guide as I have just rebuilt the engine so everything should be working to spec. with all nice new parts.
    #4
  5. Edbert

    Edbert Founding Member

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    I agree with Ozsum, but since he can't get to a dyno...

    The "Shelby-ized" K-code 289 got 306HP, that was by adding a manifold, headers, and carb to a 270 horse 289. That cam is fairly stout (much more so than the K) and the 351W valves really outflow the K heads. So I'd guess you are in the 320-330 range.

    Like OZ said, these are just guesses, and like opinions...well, you know :D
    #5
  6. Ozsum67

    Ozsum67 Too much thin air Founding Member

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    Another thing to conside is the accuracy of the stated HP ratings from the manufacturers due to pressure from insurance companies or just bragging rights. The starting point may not be a starting point at all.
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  7. Jonstantine

    Jonstantine Founding Member

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    with that huge cam, you could probably make a ton of power with some new aluminum heads

    the shelby's were probably rated with no accessories

    im gonna guess 300 at 6k rpms
    i dont think your low end torque is going to be all that great
    #7

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