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Old 01-02-2003, 06:36 PM
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Exclamation Build for Hp or Torque?

Hello all,

Recently for the sake of going faster, I traded my mild 355 for a BBC 396. As far as the buildup goes I have a pretty good idea of what I'm doing but I have a cam selection question.

I've been using desktop dyno to get a ballpark figure on HP and TQ numbers. Right now my setup will make around 450 hp and 440 ft-lbs But I notice If I change cams around a little bit I can make 400ft-lbs and 560 Hp and with more tinkering i can make 550 ft-lbs and 400 hp and so on.

I'm guess my question is, Whats more important in a 3400 pound street car More torque or More HP? or the highest close to even numbers I can muster?


Also, With plaing with more cams I can change the overall output. For example, With one combo I can get about 475HP and 480 FT-lbs (at peak) but with an average that is only in the 330's Where-as the combo I'm building now peaks around the 440-450 area but has 380-400hp-ftlbs from 2.5k-6000 rpms.

More peak power or more power across the board?
More horsepower or More torque?

Other info of intrest 3400 pound car w/driver and full of junk, 3.73 gears Daily driven everywhere. about 4000 highway miles a year. streetable? whats that?


Thanks in advance If anyone need any more info just let me know

Brandon

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Old 01-02-2003, 06:49 PM
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I suggest Horsepower......

In a 3400 lbs street car, a lot of torque blows the tires away. With the high Horsepower, you can get it out the hole with less wheelspin and as the power comes on...... the car is hooked up.


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Old 01-02-2003, 07:03 PM
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gotta find a balance... for me I am aiming to have a bit more tourque than HP on a 3200lbs car... It will light up the tires alot but whatever... thats all I do anyways... if I ever get into a real drag race with slicks the tourque will be handy (for the first bit) after that I will hopefully have enough HP to keep her going to the finish...
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Old 01-02-2003, 07:18 PM
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I have to say build for the flatest torque curve, That way all of your power will be avialable right off the get go. No matter where you are in the RPM range.

Surely you intend to spend some money on the suspesion to get the car to hook off the line and thats really where your gonna get most of the fast times. If you ever watch the EZ street class of drag racing thats where all their times come from. These Stock motors leave at 6000 and the chassis permits almost no wheel spin so they somtimes carry the front tires all the way past the 60 foot! And still manage to lay down consistant 10's at 130 plus!
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Old 01-02-2003, 07:24 PM
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All of these things are important. If you have a engine that has too much torque then you compensate with tires.

The broadest torque and horsepower curve is a really good to achieve.

The best thing to do is to test all of your combos in your car with out actually installing the engine by using a computer program.

Try these guys. Be sure to read about their client's car.

<a href="http://www.pchotrod.com" target="_blank">www.pchotrod.com</a>

[ January 02, 2003: Message edited by: 2quik ]</p>
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Old 01-02-2003, 07:25 PM
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If i were u i would concentrate on Torque. Remember your car is heavy and torque helps it move faster. But it depends on what your gear ratio is. And besides the big blocks make great torque where u need it in a street driven machine. I just rebuilt my 396 with a 40 over bore and a small comp cam extreme energy 256 cam in my 67 SS396 Chevelle. If its for a daily driving machine build TORQUE. As much as u can over the broadest range possible where u can use it the most. Oh and dont worry, the horsepower will follow but more important your engine will live. Try it.
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Old 01-02-2003, 07:30 PM
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I was thinking about cal tracs and 26X9 slicks for the track, My goal is to be in the low 11's maybe high 10's with a 150 shot Do you guys think I would be able to reach those times with the 450-hp 450 tq motor? what does it take to get to the low 11's anyway?

Brandon
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Old 01-02-2003, 08:08 PM
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What gives you the most area under the torque curve and the HP curve. This is called optimization of application and will build the engine to suit its strong suits and downplay any weaknesses. Doing a area calculation is not easy and takes some hard math to figure, I'm not sure if PC Hotrod does this calc for you.

After doing the calcs you'll see what combination gives you the most area under both curves (I add them together and apply a weighting to the desired outcome HP or Torque). You see there is one that gives the highest reading total and this is the one that best suits the characteristics of the BBC.

Little hint it's always the curve that is flat and broad and extends widely across the rpm range, most people would say this is what you call a midrange engine. Me I call it eating your cake and having it too.

Gear accordingly and dyno your build to verify the calcs. Of course if all your after is good ET's then horsepower should be your goal but it makes for a inflexible street engine.
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Old 01-03-2003, 02:41 AM
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Speed cost money how fast do you wont to go? Im' a old man to most of you guys but back in the erly 70s, my 55 chevy could run the 1320 in 11.60 at 125,mph not a lot of speed but good hook up and a lot of torque, the motor was a 327 out of a 66 vet 4,speed with 413s waying in at 2900.Remember better torque less speen good hook up = better Time!! Most drag races are won or lost at the line. If you like that kind of stuff go to <a href="http://www.gassermadnes.com" target="_blank">www.gassermadnes.com</a> and look around, you might find youer ansser there,there is a lot of dragraceing stuff to look at and to read.In drag raceing there is and old saying, and I quote the quick and the dead.I go with torque.But thats' ME let us know what you go with Chuck,

[ January 03, 2003: Message edited by: Chucks,57 ] <img src="graemlins/mwink.gif" border="0" alt="[mwink]" /> <img src="graemlins/mwink.gif" border="0" alt="[mwink]" />

[ January 03, 2003: Message edited by: Chucks,57 ]</p>
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Old 01-03-2003, 06:55 AM
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In building my 455, I was after torque. The car will never see a track or high revs, so I wanted mountains of torque on low end, I'll deal with tires. It all depends on how you intend to use the car. For a street car that cruizes to drive in's or goes out for fun on nice days, build torque. If Friday comes and you want to run the track, you'll have to give up some torque and build more hp. But lets face it, with the numbers you're talking about, either way it will be a monster!!! Keep in mind, for street applications I was after the 0-70 range, I don't really care if the car does 130 or not, I'll never find out. At I can still run 3:55 gears so cruisin around doesn't cost me a fortune.
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Old 01-03-2003, 06:56 AM
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PS - I use a set of Caltracs on my TA, love em. They were easy to install and the car launches!!
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Old 01-03-2003, 09:18 AM
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<a href="http://www.prestage.com/carmath/calc_Gears.asp" target="_blank">http://www.prestage.com/carmath/calc_Gears.asp</a>

I didn't know how to make a direct link but this is a good website that lets you make good decisions on HP, Transmissions, Weight, Gear Ratio, etc....check it out....it is very cool.

-Billybob
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Old 01-03-2003, 10:15 AM
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Thanks for your replys,

Bandon
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Old 01-07-2003, 01:16 AM
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torque is what moves

horsepower is what sells

with that said it is completely up to u on what u want more of.....a car that does burnouts all day with no prob.. or a nice fast car that will hook up
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Old 01-07-2003, 04:30 PM
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hey venturat, i use that program and enjoy it. i have massaged a 383 enery way you can and right now it makes 440 hrs/513 trq @ 4500 rpms. at 6000 rpm's it turns in 519 hrs/ 454 trq. it messed with cams, compression, cubes and stroke. the one thing i find interesting and the most curve changing input is the intake. i read in some of your previous replys about a flat torque line. i hear single plane is the way to go if your gonna turn high rpms and move alot of air but if its a flat torqe line your looking for plug that dual plane into your best engine build on your program. looks like you hit it with a hammer. anyway good luck. bern
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