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post #1 of (permalink) Old 06-19-2001, 12:02 AM Thread Starter
 
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where is my horsepower at?

I"msure this has been discussed before, but a buddy and i got in a big debate over it...the conclusions was...we don;t know.
Where is the Hp measured at? he's got a 1980firebird T/A with a 350 out of a 78 Ventura. engine is rebuild with a crane cam and flat top pistons...but thats about it. he wants to know roughly what Hp he's got...and it made me curious too. what do i have and where is it measured at? I've got the Vortec 350 with coldair K&N, and dual flowmasters...oh and Z-71 stickers so make sure to add in the xtra Hp that gives me...yeah right. thatnks fro the help
---Peacock

<font color=red>96 Z-71 EXTcab, richmond 3.73, detroit rear, cold air, dual flowmasters, new drive-train </font color=red>
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post #2 of (permalink) Old 06-19-2001, 12:28 AM
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Re: where is my horsepower at?

if you want your actual HP that's hitting the ground, then you measure at the rear wheels. the # at he flywheel will be higher...there is power lost before it gets to the ground at the wheels.



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post #3 of (permalink) Old 06-19-2001, 12:30 AM
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Re: where is my horsepower at?

well, the posted HP that manufacturers, etc claim is flywheel HP which can only be measured (to the best of my knowledge) on an engine dyno with the engine out of the vehicle. what everyone SHOULD use is rear wheel HP since thats what matters. this is measured by strapping the vehicle where the rear tires are on top of two big drums attached to computers and you make a few runs in the vehicle to certain speeds and RPMs and the computer figures out hp/torque and the curve for each. your HP is prob around 250 at the flywheel

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post #4 of (permalink) Old 06-19-2001, 12:31 AM
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Re: where is my horsepower at?

there two spots, dyno or rear wheel. dyno is hooked up to the crank shaft, transmission removed. rear wheel, is just what it sounds like, drive it onto the rollers and let it rip. by the way, you lose a lot of power before it gets to the rear end but basically all measurements are made dyno, example, the honda s2000 "has" 240hp, thats dyno, and no torque really, so its not going anywhre.
if you know the original hp of your motor (vortec is 250 or 255 i believe) add whatever upgrades you have, can't remember what caldair k&n is, the replacement is 5hp i think. with the replacement you would have 260hp.
and im ranting again, im done

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post #5 of (permalink) Old 06-19-2001, 12:02 PM
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Re: where is my horsepower at?

If you want a figure on a paper it goes like this...HP = atmospheric pressure (14.7 and depends on altitude) X cubes x Compression Ratio x rpm (peak operating hp of cam) X VE (Volumetric Efficincy. Depends on heads and intake..mild street is around .85) divided by a constant of 792000. So if you have a 350 with 9 to 1 compression, with a reasonable VE of .85 and the cam peaks out at 5000rpms it looks like this.

HP = 14.7 x 350 x 9 x 5000 x .85 / 792K = 248.5 hp (flywheel)

Then add Z71 sticker magic index of X 1.65 per sticker. You got one? = 410 hp. You got two? Oh man, 676.5 hp !!! Your standard drivetrain will suffer severly if you have 4 stickers because that equals 1842 hp !!![img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/laugh.gif[/img]

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post #6 of (permalink) Old 06-19-2001, 12:28 PM
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Re: where is my horsepower at?

he he! that was pretty funny. college courses should be taught that way.

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post #7 of (permalink) Old 06-19-2001, 08:11 PM Thread Starter
 
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Re: where is my horsepower at?

well nuts to the 383stroker then. I"ll just head to the dealership and get some more sitchers. do they have to be adhered to the body, or is a window ok?
thanks for the info and the laugh guys
--PEacock

<font color=red>96 Z-71 EXTcab, richmond 3.73, detroit rear, cold air, dual flowmasters, new drive-train </font color=red>
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post #8 of (permalink) Old 06-19-2001, 09:31 PM
 
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Re: where is my horsepower at?

I got a question on this topic...back in the old days, like the '60s, the hp advertised was always gross hp, right? Then they changed to net, which is at the rear wheels, whereas gross is at the flywheel....so, why are the Vortec's 250 or so at the flywheel? Did they go back to gross, or I am confused? thanks

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post #9 of (permalink) Old 06-19-2001, 09:34 PM Thread Starter
 
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Re: where is my horsepower at?

thats my very question...do i have 270 (exhaust, cold air...etc) at the flywheel, or at the rear skins?
--Peacock

<font color=red>96 Z-71 EXTcab, richmond 3.73, detroit rear, cold air, dual flowmasters, new drive-train </font color=red>
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post #10 of (permalink) Old 06-19-2001, 10:55 PM
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Re: where is my horsepower at?

If I remember correctly, gross HP was measured with a stripped down engine, e.g. alternator, A/C, etc were removed so that they would get the actual HP that the motor was putting out without any power robbing accessories.

The net HP was calculated with all the engine components connected.

Neither one of these really tells the story. The only thing anyone should be concerned with is HP at the rear wheels since that is all you can use anyway

1994 Z71 350, Xcab, Sportside, 285/75/16 BFG AT. Trailmaster 4" lift
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