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Thread: Put the slicks on

  1. #11
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    Quote Originally Posted by Rick_L View Post
    "Taller" gears means less rpm at a given speed, not more. You want "shorter" gears, which are higher numerical.

    For formulas like this, it's not horsepower at the flywheel, or "horsepower used" , it's horsepower applied. Because that's what's known. Any implication of horsepower at the flywheel is an assumption of the drivetrain efficiency, including tire spin, converter slippage, power loss in the transmission and rear axle, etc.
    Just when I thought I had the "tall" and "short" gear lingo I used it backwards.

    OK, so are you saying the HP calculators that use weight, distance and time are bull?
    Tony

    1955 Bel Air Sport Coupe

  2. #12
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    Quote Originally Posted by 55 Rescue Dog View Post
    Gearing is more about torque multiplication, not horsepower anyway. If you pick a dedicated drag gear like a 4:11, unless you trailer it, it won't be much fun to drive to the track or anywhere else without buzzing that BBC at 4000RPM plus just going down the highway. Tire diameter is one factor, and determine what speed, and redline engine speed will be when you trip the lights. You wouldn't want to hit redline in high gear before you even get there. A G-force meter app, or similar can calculate horsepower, 0-60, 1/4 mile times, etc. You are also pushing a big shoebox into the wind. I would look at torque converters, not knowing what you have now, or how much traction you have,.
    Driving to the track will be no problem, it's just over 1 mile away. I drove it there and home with the slicks. Now with rpm calculators they are a lot better except allowing for converter slippage and I get this:
    Now with 3.42 28" tire 70mph I'm at 2873rpm
    switch to 4.11 gears and I'm up to 3452rpm
    get the 4L80E I've been planning on and I'm lower than now at 2589rpm. Right?
    Tony

    1955 Bel Air Sport Coupe

  3. #13
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    Quote Originally Posted by 55 Rescue Dog View Post
    Tire diameter is one factor, and determine what speed, and redline engine speed will be when you trip the lights. You wouldn't want to hit redline in high gear before you even get there. A G-force meter app, or similar can calculate horsepower, 0-60, 1/4 mile times, etc. You are also pushing a big shoebox into the wind. I would look at torque converters, not knowing what you have now, or how much traction you have,.
    No redline problem that I see with 4.11's and a 5500 redline I'll be good for 105mph or so. I don't think I'll be doing that in an 1/8.
    Tony

    1955 Bel Air Sport Coupe

  4. #14
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    Quote Originally Posted by 55 Tony View Post
    Just when I thought I had the "tall" and "short" gear lingo I used it backwards.

    OK, so are you saying the HP calculators that use weight, distance and time are bull?
    Rick is correct. Those calculators give the horsepower applied to the rear wheels.
    Dave, from the old neighborhood in Jersey!

  5. #15
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    Quote Originally Posted by chevynut View Post
    Don't know how accurate this is.....

    http://www.wallaceracing.com/et-hp-mph-8th.php

    "Your Flywheel HP is 287 computed from your vehicle weight of 3600 pounds and ET of 8.52 seconds."
    Wow, I can't believe it gives flywheel horsepower. It has to assume a lot of variables. I wonder if that's a mistake and it really should be HP at the drive wheels.
    Dave, from the old neighborhood in Jersey!

  6. #16
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    My old 70 SS Chevelle with a 76 peanut port truck motor with a .500 lift marine cam used to do 1.98 60ft and 14.0 1/4s with 3.31 gears and 255/60/15 Goodyear radials. I forgot stock fuel pump and Holley 650 spread bore. 8.50 in the 1/8 is pretty good for a turtles 60 ft. If I recall Tony is opposed to buying a real torque converter which would fix the 60 ft issue.
    Last edited by markm; 03-18-2018 at 04:45 PM.

  7. #17
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    OK, so are you saying the HP calculators that use weight, distance and time are bull?
    Not at all. Just that they are calculating AVERAGE, not peak, power at the wheels. Any extension to flywheel hp has to assume some kind of loss through the drivetrain. And remember it's average over the entire run.

    The 4.11 gears you are considering will raise the engine rpm over the 1/8 mile. This will in turn mean more average horsepower because of the higher rpm.

    I would not get too concerned with these numbers until you take it to a real track with real timing equipment and verify that the numbers you're now getting are even in the ballpark, because they may not be. markm's comment about a peanut port BBC going 1.98 in 60' with similar gears to yours is spot on. Your setup is either a dog or your timing numbers are suspect.

  8. #18
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    Quote Originally Posted by markm View Post
    My old 70 SS Chevelle with a 76 peanut port truck motor with a .500 lift marine cam used to do 1.98 60ft and 14.0 1/4s with 3.31 gears and 255/60/15 Goodyear radials. I forgot stock fuel pump and Holley 650 spread bore. 8.50 in the 1/8 is pretty good for a turtles 60 ft. If I recall Tony is opposed to buying a real torque converter which would fix the 60 ft issue.
    Oh markm you. Stop buttering me up. I'm not that kind of guy.
    Tony

    1955 Bel Air Sport Coupe

  9. #19
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    Quote Originally Posted by Bitchin'57 View Post
    Wow, I can't believe it gives flywheel horsepower. It has to assume a lot of variables. I wonder if that's a mistake and it really should be HP at the drive wheels.
    They make an assumption of drivetrain losses to come up with flywheel horsepower. I think they typically use around 15%.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
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    2003 Chevy Silverado 2500 HD Duramax
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  10. #20
    Registered Member chevynut's Avatar
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    Quote Originally Posted by 55 Tony View Post
    OK, so are you saying the HP calculators that use weight, distance and time are bull?
    It's just physics and math.

    If you put 3000 pounds of force on an object and push it 1000 feet, you've done 3,000,000 foot pounds of work. That's how much energy you used to push it that far, no matter how fast you do it. The time element is where horsepower comes from. If you do that amount of work in 10 seconds, you've done 300,000 ft-lb/second of work. If you divide that by 550 ft-lb/second = 1 HP you get 545.45 HP. So it takes that much horsepower to do that much work in 10 seconds. Less time takes more HP, or conversely more HP can do the same amount of work in less time.

    Horsepower isn't measured directly. It's a calculation, even when using a dyno. What they're doing is measuring torque at various RPM intervals, and calculating HP at those same intervals. HP = torque x RPM. At 5252 RPM horsepower and torque are equal, i.e. 400 ft-lb of torque ALWAYS gives you 400 HP at 5252 RPM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

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