HP calculator

Discussion in 'Race 400/430/455' started by BQUICK, Nov 13, 2003.


    BQUICK Well-Known Member

    Went to Speedworld site to use their HP calculator.

    According to their calculator my motor made 876 HP at the flywheel and 742 at the wheels!
    I seriously doubt it! Must be those little Chevy ponies!

    I figured more like 700 at the flywheel and 625 at the wheels.

  2. Staged70Lark

    Staged70Lark Well-Known Member

    Hey Bruce,

    Some of these calculators are way off but still fun to play with. The only HP calculator that I have found to be fairly accurate is the Moroso Power Speed Calculator 89650.

    If you put the slide rule at the ET or MPH it will give you an approximation of the HP for a given weight. Now... to figure out what the flywheel hp you must do another calculation. A vehicle that weighs 1600 lbs is going to have less HP loss through the drivetrain than a vehicle that weighs 4000 lbs. Therefore I was told by Moroso that you must add about 10% to a 1600 lb car and 18% to a 4000 lbs car. Again these are approximations but fairly close.

    Your car
    3700 lbs @ 10.30 = 610 Rear Wheel HP (RWHP)

    Now go 610 + 18% = 719.8 Flywheel HP (FWHP)

    OK... now how much additional power must an engine make on a given day to go 10.00s

    3700 lbs @ 10.00 = 670 RWHP ... thats a bunch more

    670 + 18% = 790... WOW...

    Now this is where I agree with Jim W. I doubt an engine like yours would make 790 HP on the dyno in a controlled environment. But 720 is surely possible.

    Take Care and Keep that thing flying!!

    BQUICK Well-Known Member

    Thanks John.
    That's amazing to me.....
    It's turning out to be a happy motor. Good OP, quiet.
    Put over 100 passes on it this year.

    I used the "cheap" machine shop on this one so I wasn't expecting much. Crap shoot sometimes.....

    Plan to run NMCA and PRO Edelbrock next year plus most of the Buick races.

    Take care////Bruce
  4. Mark Dalquist

    Mark Dalquist Well-Known Member

    Hey John- a friend of mine has an actual calculator that when you punch in the numbers it comes up with power/ET/mph. We calculated my car at 4550 lbs and a 12.07 @ 109.49 mph pass. The answer we got was 503 hp at the rear wheels which would be over 600 at the motor. I have always thought that this sounded a little stout and I was wondering if you could punch these numbers into your Moroso slider and see what it says. I would believe 450 at the wheels or possibly less but that other number seems suspicious:puzzled:

    Thanks if you can do this for me-------Mark D.
  5. Jim Weise

    Jim Weise 1000+HP


    If you have the data..

    Give me the buildup, and I bet I couild guess within maybe 10-20 HP what that would put out for corrected numbers on the dyno..

    I knew all that money I spend over there would come in handy someday.. :gt:

    I need to know:

    Compression ratio
    Camshaft intake duration, lobe center and where it is installed
    Intake manifold used, and carb, and exhaust
    Head flow numbers

    And any other little goodies, like windage trays, deep oil pans and such..

    No.. I'm not any kind of savant.. just have a dyno logbook here, that's about as big as a good size metro area phonebook..

    I think I have spent a couple grand on the dyno shop this year, and I am going again first thing in the morning..


    BQUICK Well-Known Member

    Hey Jim, here you go:

    .038 455
    12.2 true comp
    260/268 cam , 108 (+adv 4 deg)
    Wildcat intake, 1050 Dom, 2.125 headers with 18 in extensions, no mufflers right now
    head flow at 28 in 308/225 @.500 (Stage 2)


    BQUICK Well-Known Member

    Oh, Stef's pan with homemade windage tray, too.

    BQUICK Well-Known Member

    here it is with future racer.....

    Attached Files:

  9. heffsstage2

    heffsstage2 Member


    Hey Bruce.My brothers engine dynoed at 726 and 648 and it runs 10.00s at 134.5 all day long.It weights 3855 with me in it and we run it through tailpipes.It usally sixty foots at 1.40 to 1.42 , but its hooked solid.It has always been lazy off the line, but runs good on the big end.Its running stock springs homeade southside bars and homeade adjustable uppers , with a 13 year old air bag.As a side note , it has 60 footed at 1.35 with a 175 shot of n20 off the line, and it never spins.This is on 9 inch slicks..I believe some of the other eliminator cars are in the 1.37 range without nitrous, laughlin hart,etc, but im not positive.Hope this helps ya .Take care th.
  10. Dubuick

    Dubuick CMDR Racer

    My set up very simular to Bruce's but t/a 508s cam +4adv. ,heads flowed 328 248 at .600 ,same comp. t/a sp1 intake with 1000+hp 4150 holly ,deep sump pan
  11. Jim Weise

    Jim Weise 1000+HP


    0 deck?

    If so, on the dyno I work with, to corrected conditons (29.92 Bar, 72* dry air) it would put out 640-655 Hp.

    Now, when you take that motor, and run it at 30.6 Bar pressure, and 40* air, it will certainly put out more.. I would say closer to 680 HP..

    Points of reference used for my estimation..

    This year, I built a STG 2 464, 11-1 compression, 320 cfm STG 2 SE heads, 260/266 solid cam, SP-1 intake 850 Holley.. Block girdle motor with stock oil pan.

    That motor made 625 HP.

    Add 10-15 HP for your higher compression..

    Oil pan is about a wash, because you don't have a girdle. So clearance to the pan, from the spinning rods will be roughtly the same.. and that motor had one of my windage screen setups in it.

    Your Wildcat and Dominator are worth 15-20 HP.. over the SP1 and 850.. most of that coming from the carb.

    Cam is close, but you have a tighter lobe center.. that is worth more power in the middle of the powerband, than it is at either end. Penalty is idle quality.

    Another point of reference..

    Before we got involved with George Sweesy's car, it weighed 3250, (with a less than ideal tube chassis, so his short times were never real great- 1.39 was his best) but with it's 680 HP iron head roller cam motor, it did manage a 9.92 at 135, in BG, about 5 years ago, in considerably less than ideal air.

    Third point of reference is another motor I built this year.. 494, 12.8-1 compression, SP-2 and STG 2 TE heads, that flowed 350 cfm.

    1150 dommy and a 308s (268/274 108 LC).

    That motor made 710 HP.

  12. Staged70Lark

    Staged70Lark Well-Known Member


    Here are the numbers for Sweesy's car when it weighed 3250 lbs calculated by the Moroso slide rule.

    9.92 at 3250 = 615 Rear wheel HP.

    Now... 615 + 15% = 707.25

    Still... pretty close.

    Take Care
  13. Dubuick

    Dubuick CMDR Racer


    What do think of the t/a 508s cam do you think that is to big for my set up? and the deck hieght is at 0
  14. BQUICK

    BQUICK Well-Known Member

    Thanks for the info Jim!

    My deck on this motor is .020. Figured I'd leave some for the next cut when I'll pick some comp up. Also figured a little less compression would be a little easier on the parts....

  15. BQUICK

    BQUICK Well-Known Member

    stg2.jpg Found this old thread......same motor still in car....lost track of number of passes....amazing to me.....
    Last edited: Oct 5, 2020
    70 GMuscle likes this.
  16. pedalit2win

    pedalit2win Well-Known Member

    Great thread! Excellent info.

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