torque vs horsepower - Team Camaro Tech
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post #1 of 10 (permalink) Old Jan 13th, 01, 04:14 PM Thread Starter
 
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What's more important for the street (stoplight to stoplight)/ or 1/8 mile drags, torque or high horsepower numbers? I've allways felt torque. So since I aquired my Desktop Dyno I have been working on an engine combo to be very mild yet yield big torque numbers. I have been using a theory I have had about camshafts so have been using various "custom grinds" I've had in mind. I finally hit on one that, at least on paper, looks like it would be a real killer in street/ 1/8 mile (short) drags. What do you guys think? The engine combo is VERY mild: 383 chevy, wedge heads stock valve size-2.02 pocket porting, 10:1 cr, 750 carb, dual plane, small tube open headers, hydraulic cam (my timing numbers). This engine combo produces OVER 400 ft.lbs. of torque from 2000 rpm through 5000 rpm ( I like high flat torque lines). Horsepower maxes at 5500 rpm with 414 hp. Your input: keeper or throwaway. I have run alot of the major cam manufacturers grinds against mine and none I have tested can duplicate this high, flat torque curve. They can produce more PEAK torque numbers for a much shorter rpm range, and higher peak hp. But nothing as wide and flat. Whatcha think?
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post #2 of 10 (permalink) Old Jan 13th, 01, 07:05 PM
 
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b-boy,

Theres a small block hydraulic cam out that does pretty good for a little bugger.

Something like 266/266, 209/209, 109/105, .414"/.414". It is a roundy round cam that does ok in the street rpm range.

If it is ground as a high lift solid, it would be better.

Is your custom grind a scale up of something like it???

Please do a search for this stuff because I've posted info on it in the past. It is fascinating to me. pdq67



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post #3 of 10 (permalink) Old Jan 14th, 01, 05:28 AM
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Torque is where its at! I have done similar simulations on the desktop dyno using the same ideas...one that I found (but had a hard time believing) was when I was playing with the numbers for a friend of mines truck. Since he already had 9.7-1 compression, small tube headers and duals, a dual plane intake and 600 cfm carb, and ported 305 HO heads, I tried some different cams (many of my own specs) and per the program, a stock gm 929 cam (300hp 327, or standard 350 cam, whatever you want to call it) made something like 416 lbs-ft at about 2500 rpm with a dead flat torque curve up to about 4500 rpm...of course it then hit a brick wall but that wasnt the point...we was looking for max torque. I think it would be interesting to build an engine like this and see what it would do in the real world. Unfortunately, us mere mortals cant afford to build engines just to test theories . I always thought it would be so cool to work in performance engine shop where you could play with stuff like this.

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
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post #4 of 10 (permalink) Old Jan 14th, 01, 05:41 AM
 
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travis,

You are talking about the same stuff I have generally found out. I know Dyno2000 is just a simulation program, but the trends in camshft selection when ran through it for a given family of cams is real neat.

The -929 cam was a very versatile cam, was used in (I think) everything from the 195hp/283 two barrel engine, through the 300hp/327 four barrel, next, the 295hp/350 and finally the 265hp/400 engine.

The -929 cam made the little 283 quite a runner and the 400 just a low rpm powerful one.

It would be neat to grind a solid high lift version of it and then look at the torque production.

This might sound stupid, but I'm wondering if the little -097 Duntov solid just might be that cam. Although, older in technology and lower in lift. But, hey, it's technology may not be that far off since it is a "tight-lash" cam.
pdq67



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post #5 of 10 (permalink) Old Jan 14th, 01, 11:26 AM
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I ran my motor - 406 SB, AFR 195 heads, 10.5-1 compression, RPM intake and 750 carb, and small tube headers - through DD and found the same thing with various cams. The smaller I went, within reason, the broader and higher the torque curve. Hydraulic roller cams really pop the numbers up all by themselves! I ran a Comp Cams hydraulic roller (XR258HR-10) with this combo and ran at 500+ ft.lbs. of torque from 2000 rpm up around 4500! Of course, you have to watch cylinder pressure buildup. The larger cams will bleed off some cylinder pressure with the more duration and a little overlap.

I think a good approach is to balance the torque and hp curves so the motor doesn't fall flat at 4500 rpm. I just ordered a CC hydraulic roller at 230/236 and .510/.520. This should give me close to 500 ft.lbs. and 500 hp in a nice broad curve.

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Scott
'69 400SB, Richmond 5-speed
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post #6 of 10 (permalink) Old Jan 14th, 01, 11:30 AM
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I forgot to address your original question. Torque is what moves the car, however, if you have a powerband that is from 2000-4500rpm and then quits, you have to match the trans and gearing to that fairly narrow powerband. IMO, you're much better off if you choose a soild torque curve supplemented by a HP curve that picks up where the torque tails off. This way you get a much wider powerband and the car will be more fun to drive.

------------------
Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1
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post #7 of 10 (permalink) Old Jan 14th, 01, 12:24 PM
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I definately agree with this last reply. Torque is only good if you match it with horsepower! At some point you are going to want too drive really fast and that is what horsepower is for.
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post #8 of 10 (permalink) Old Jan 14th, 01, 02:21 PM
 
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DanL,
All that has happened is that the torque curve has slipped sideways towards the top end and this is actually what produces the big hp numbers.

You lose a little low end torque and pick up high end torque as indicated by the big hp numbers. IMHO, pdq67



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post #9 of 10 (permalink) Old Jan 15th, 01, 04:05 AM
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One of the kids I race with has a 3rd gen Formula Firebird. He worked the motor for torque. The cam he picked it not far off from a stock grind and this car rides out of the hole. It will hit a "brick wall" after about 5,500 rpm, but it is a rocket up til then. Car runs high 12's, but it doesn't sound like it. Great sleeper!

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------------------
Mark

1992 Firebird 355/Six Speed (Soon to be LT1)
1991 RS 350 / 700-R4
1987 Toyota Pickup 383 / 500 + HP 10.963 @ 119.95 Slicks / 11.997 @ 114.23 Radials
"Speed KILLS, so drive a FORD and live forever!"
http://personal.lig.bellsouth.net/~racer383/
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post #10 of 10 (permalink) Old Jan 15th, 01, 04:33 PM Thread Starter
 
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Just got back to this post. Thanks for the input, guys.
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