horsepower or torque?

[keithq69]

I'm building an LQ4 for a 69 Camaro.
The car will see mostly street use but I do plan on track days. Just lapping, no racing.
I'm trying to decide if I should run the 317 casting heads and a cam more suited to torque which should put me somewhere around 430-470hp from what I can see. The other option is to go with the LS3 heads and intake with a larger cam to bring hp over 500 with a loss in low end torque.
I don't know if the loss in torque will make much difference on the street since the engine should still make respectable torque numbers.

What's better for the track?
The lower RPM range of the torquey engine appeals to me from a durability stand point but the high RPM appeals to the boy racer in me.



Keith.

[keithq69]

A few things I forgot to mention, I've got Eagle I beam 6.125 rods with ARP bolts and Mahle forged pistons with plasma rings.

[DirtShark]

Coming from a Sprint Car racing background, torque is king, horsepower is a number we get to tell all our friends about. Horsepower looks good on a dyno sheet, and torque actually gets the job done...

[BuzzKillian]

Torque is where it's at! It pulls you out of the corners, away from a light and generally just gets the job done. On the street or on the Autox... I want torque.
From what I have seen, LS engines make good flat torque curves. That being said... I still wanna spin it 6,000-6,500 LOL

[keithq69]

Thanks guys. I enjoy the torque too, I'll stick with the cam I chose and the ported 317 heads. It should still make close to 500hp at the crank.

One more question now, should I go with a standard weight flywheel or a lightweight one? The stock one seems to be about 28lbs and a chromoly SFI flywheel is about 20lbs.

[SSLT1KID]

Horse Power sells cars. Torque makes them fun to drive.

[CreepinDeth]

What's better for the track?

Horsepower IMO. You'll still have plenty of torque to get the car moving out of a dig assuming your suspension
is putting it all to the ground and not sitting and spinning. After that, horsepower is what will win the race.

Oldsmobile 455's were stump pullers with 500ft lbs of torque and 365hp (Gross) but only did 14 seconds in the 1/4.
Torque gets you moving off of the line, but horsepower is what helps you beyond that.
Now if those Oldsmobiles had 500ft lbs of torque AND 500HP they'd be a BUTTLOAD faster.

Emissions helped kill the muscle car and Horsepower era, but torque remained.
How fast were the mid 70's cars with choked off horsepower ?? Slow as dogs even with torque.

Example:
a 1978 Camaro Z28 had 280ft lbs of torque, but only did 17 seconds in the 1/4 mile.
Why ?? Because it only had 185hp. Proof that torque isn't the only thing you need.

With Ricer/Tuner cars you have the exact opposite, and that's why they do "From a roll" races.
Because they have higher HP but no torque to get them moving off the line fast enough.

[Norm Peterson]

It isn't entirely appropriate to use dragstrip-based observations as a basis for what street driving and a variety of road course activities really need.

Drag racing is specialized enough that you're hardly ever running the engine at revs below upper midrange, nor is your speed at any given instant affected by other traffic. Short of the guy in the other lane drifting into yours, anyway, which is something that can happen anywhere.

Street driving and open-tracking involve using rpms much lower into the midrange, and you spend relatively little time at peak HP revs. You aren't always going to be coming off the corners at the same rpm that a dragstrip upshift @redline would drop you back to, either. There's simply too much variety of cornering speed, so unless you've got so much torque that you can blow the tires off in 3rd gear at will, having a torque curve that's fatter through the midrange will be more useful than having a similar number of extra HP up top where you hardly ever get to use it.


I understand your examples, but the 1970's cars were torque limited and rev limited as well as power limited. 280 ft-lbs from a 350 is nothing to write home about and all done by 4200 means you certainly didn't trade torque for HP.

Let me offer another comparison - even with the stock tune the 4.6L in my Mustang made 35 ft-lbs or so more peak torque than 1978's Z28 5.7L. It makes almost 280 at the factory redline (6000) after a very mild tune, from over a whole liter less displacement. And it still isn't anywhere near being either a torque monster or a HP freak.


Norm

[Zachalanche]

for a 100% dedicated track car I would choose an engine that makes a lot of HP at a high rpm, but it would have to be geared correctly to make use of that hp. For most other applications you should be looking for the most area under the torque curve. for examle, my street bike has around 115 hp which would be considered a high hp motor for only having about 40 ft lbs of torque. the engine can run in excess of 17,000 rpms, so it takes a lot of hp to maintian any torque at that engine speed. the result is a torque curve that looks relatively flat from 5000 - 17000 rpms. while the peak torque isn't very impressive there is a huge area under the torque curve nd that's what makes the bike much faster than many bikes that have near double the peak torque.

Engines that are considered to be torqy (more torque than HP) make thier peak torque well before 5252 rpms butter that speed the torque is in the dirt. in this case there tends to not be much area under the torque curve. hopefully you have high gearing and a massive amount of torque here, because you will be shifting very early.

Bottom line is, that you wantas much torque as possible throughout the entire rpm range, but to make lots of torque above 5252 rpms you have to make more hp than torque. and sometimes you have to trade some low end torque to gain top end torque, but if the area under the curve increases they you have benefited.

as a starting point you really need to know what rpm range you will be running. then try to make as much torque as you can through that range. you will likely end up with more hp than torque. If you don't, that engine would be better off pulling a trailer.

[AMC Racer]

Power = rate of doing work. Torque = work
So horsepower = how fast you can apply the torque. So more hp = faster ... if it's geared to work in the rpm range of peak hp. A broad torque curve will give a broad hp curve.

People talk about strong low end and mid range torque, but that also equals strong low end and mid range hp. If it's a typical performance street build with typical street gearing, choose a cam that gives peak torque around 4500 rpm which should give peak hp around 6000 rpm. Go with a bigger cam with more gear, smaller with less gear.

1 hp = 550 lbf.ft / sec
tq = lbf.ft
if speed = rpms = revolutions / min = 2 pi radians / min = (2 x 3.1415)/60 sec/min.

So hp is simply the mathematical conversion of torque @ rpm:
hp = torque x rpms = lbf.ft x rpms / [(550 x 60)/(2 x 3.1415)] = torque (lbf.ft) x rpms / 5252

[SRD art]

A few thoughts from my specific experience...

My street strip 406 small block powered Nova makes 511 ft lbs at 5000, 562 flywheel hp at 6500. BUT because of the cam/ engine design it doesn't make enough power to break the drag t/a's loose below 3000, even with 4.56 gears. Case in point, I was running a 4500 stall converter and the car pulled 1.63 60' times. On the street I could boil drag slicks for all of 1st and into second. When my converter went south I threw a 2200 stall in there for a bit just to keep it driveable. Off the line it would take off smooth without even a chirp. Then when it hit 3500 it would break the tires loose and spin into second gear. My point here being useable RPM range is a just as important part of the equation.

My wagon with a mild 406 small block ran 15.7's at 84 mph, at 4500 ft altitude. It dynoed 222 hp and 281 ft lbs at the wheels. It had 2.41 gears at the time so the car was a dog off the line. With 3.73s it would've been much quicker. Point here- as has been said all of the car's components are an important part of the equation and have to be matched to maximize performance.

I've seen some old photos and a couple old videos of those Road and Track style car test from the 70's. I take those 1/4 mile numbers with a grain of salt because half of them showed the car boiling the bias 8" wide tires for half of first gear. I don't know specific stats so just a made up example- if a right off the showroom floor 72 Olds 442 with a 455 that made 250 hp and 500 ft lbs ran the 1/4 at 15.5 @ 105 mph using a suction cup wheel meter for the magazine road test, there's a good indication this is a low 13 or high 12 second car that can't hook worth beans.

Considering the above example, with the right driver that can control wheel spin, low end high torque always wins in short spurts- like light to light racing, autocross, changing lanes to get around the semi, good fuel economy while cruising at 2500 rpms on the freeway, etc. This is why I'm keeping the 5.3 truck intake on my motor and building it for torque. As a daily driver and once a month track car I want all the power I can milk out of it between idle and 4000 rpms.

Hope this all helps in some way.

[parsonsj]

Power = rate of doing work. Torque = work
So horsepower = how fast you can apply the torque. So more hp = faster ... if it's geared to work in the rpm range of peak hp. A broad torque curve will give a broad hp curve.

Exactly.

Torque and hp are not two distinct choices, one being better than the other. HP is derived from torque, and as such it makes little sense to discuss them as separate entities. A more meaningful conversation is to discuss RPM and torque separately, optimizing your gearing based on your rev limits.

[keithq69]

Agreed John. That was kind of my question, lower RPM range or higher RPM range.

From what I've found, the engines with the LS3 heads make more peak hp when using a cam to make the most out the flow but give up some torque below 3500 rpm.
The 317 heads make more torque in the rpm range that I will use the engine most.
I know that hp is a function of torque and that gearing, vehicle weight and rpm range all play a factor.
I would think that both engines in my 69 Camaro geared optimally for each engine one would be faster than the other.
Maybe I'm thinking it through too much, I should just pick what I prefer.
From driving some other cars that are designed for track use I find they usually go for the higher rpm range with less low end torque and gear them accordingly.
My brothers Aston Martin Vantage doesn't have much low end torque but really comes alive above 4000 rpm. It's fast on the track.
My friends R8 V10 is the same, the max torque comes in above 5500 rpm I think and peaks under 400ft/lbs. it makes 525hp and redlines at close to 8000 rpm.
The car is geared for that rpm and low torque. It will only do about 25mph in first gear at 7500 rpm but it accelerates like crazy because it's geared properly.
In contrast the Z06 makes about the same power at a lower rpm with much more peak and low rpm torque. With the stock gearing it will do almost 55 mph in first gear at redline. If gets to 60 mph as fast as the R8.

So I guess gearing really is the key.
I've got a 3.50 in the 9" and I'm going to run a T56 magnum so I have a choice between 2.66 and 2.97 first gear.

[TraviZ28]

A lot of reading in this thread. I come from my love of third generation Camaros. Back then the best models were rated 245hp and and an earth shattering 355ft-lbs of torque. They were fun off the line but the top end and overall acceleration was mediocre at best.

[Vegas69]

The most average power in protouring wins.

[DirtShark]

The most average power in protouring wins.

Agreed, look at the very last line on the dyno sheet it will tell the real story...

[MonzaRacer]

OK basic idea is make as flat a torque curve as you can up to red line.
Torque is used to computer horsepower with cid, rpm and torque in proper equation.
For a street car torque is king, teamed with proper converter and proper gears and proper tires you will have a fun car and quick.
For a track car your torque king wont run as well as you need the power in a different range, BUT it will be a major dog on bottom end compared.
Figuring air flow numbers for your engine help, then deciding which cam puts you in the rpm range you NEED.
If your heads flow good at 3500-5500, then your gonna need a push car and airplane gears. If you get heads that can flow and run well into the 6500-8500 range and not lose flow and quality then cam it for high rpm (means call cam company you like) thye have their programs and information on their parts.
I built a near stocker 355, put in a small cam to run in buddies race car till his 327 was done, he bowed out of racing so i got my engine back,,,decided to open up some heavy truck 991 heads to run bigger 1.94 intakes(came with 1.74) did my raising of guides a tad in ports, bowl work and an old Edelbrock Scorpion intake and 600 Carter, ran a TCI Saturday nite Special converter/TH350 and 3.42 gears and 275 60 tires,,,car was VIOLENT and had awesome traction. (3k lb 77 Monza).
BUT up top it lacked a lot,,,switched on my 780, it really got violent and fun.
This cam was a Lingenfelter designed hyd made to run with an older Accell Super Ram, so I know it was super tame compared to lots of cams.
It was split lift/duration mild cam.And swap meet cheap.
Making power at higher rpms for track work is tantamount to a fun,fast car.
But daily driving may be little more laid back.
Engines produce torque, horsepower comes from the torque numbers recorded on dyno, and the HP equation.
How about a step or two bigger cam that still matches the heads and make sure you have proper gears so your not rpming the crap out of it,,,oh and buy good rods and pistons for spinning anything higher rpms. Or at least good bolts and studs.

[RSX302]

My preference leans a little more toward HP on mostly street use. Anything over 400-450tq will be a tire roasters on basic street rubber anyway. It's all about what you can put down to the ground.(what tire size and compound?) 500hp at 400tq would be a great little warrior on smaller harder street rubber. 400hp-500tq would be worse because after you are done spinning your wheels thru first and second you are ready for the HP, but wait it's lower and peters out on you at higher rpm.

If you can get traction, equal HP/Tq would be best for all around good performance for the street and occational track.

[keithq69]

I've got Eagle rods with ARP bolts and Mahle forged pistons. I'm planning on using a stud kit top and bottom too just for peace of mind.
The rotating assembly will be balanced too.
Also going with chromoly push rods, new high volume oil pump and better rockers.
I think that covers all the durability issues.

Keith.

[keithq69]

I've got a 335/30/19 Nitto NT05 on the back so traction should be decent.
I think I'm going to go with a cam that gives me a good mix of both. One that gives me enough torque to make it fun on the street.
I'm thinking maybe a 1600-6600 rpm range. I've seen a few like that.