Torque is the actual force the engine produces, hp is torque in a certain time. In an engine, hp=(torque*rpm at that torque)/5252 . So Torque is the force created, and hp is the WORK done based on torque and how quickly the engine is moving(it moves faster, the force is being applied in a faster amount of time). Basically, when you build an engine, you should really build it for best torque where you need it, and that's where a cam comes into play. Like my77stang said, you can get 4x4 cams that move the power band DOWN to get better torque for off road, but at lower rpm you won't make as much HP, and torque drops off more quickly and you don't have top end hp, but actual force(torque) iswhere you need it. As opposed to a high performance street engine, where you need more torque in the mid range and up top to get the power where you need it. As a consequence of making better torque at mid and upper rpm's, more hp is created, though torque and hp are decreased at lower rpm. So basically, hp is a function of torque within a certain rpm range, but you need torque where you need it for what the engine is used for, off road, boat, race car, street car, drag, circle track etc etc etc. That's where cam selection helps, build torque that you need, and hp comes from that. That's why too many people build engines that are pigs, they look at hp without understanding how it relates to torque, and they end up with an engine that might make decent top end hp, but in actuality has no real usable power. http://www.epi-eng.com/ET-PwrTrq.htm here's another good read

 

Thanks!! So it appears that peak HP at a specific RPM is only useful for determining the gearing and shift points. And, Torque is what you really want. If so, then the stroker motors should also produce more torque because of the longer stroke. Interesting.

 

Peak hp just tells you how much torque you're making at that rpm, and how well the torque is used(high speed means better use of torque). But peak hp, comes from having good torque at an upper rpm, the faster torque drops off, the faster hp drops off as well if the increase in rpm can't compensate. That's why some Honda's are quick at speed, not much torque, but they maintain enough torque at like 8,000rpm to produce decent hp. But they still suck off the line and drive like pigs, no bottom end. Whereas a V8 let's say, can produce much more torque down low and consequently generate more hp at lower rpms, and drive with more "gusto" at lower rpm's.

 

BTW, a lot of the terms are used differently, but in science terms, force is like weight, lbs for example. Work is force across a distance, 50 lb-ft for example, and power is work done in a certain amount of time, 50hp for example. And 1hp is 33,000 lb-ft/min I believe, ie 33,000lbs moved a distance of 1 foot in 1 minute, OR, 1 lb moved 33,000ft in 1 minute

 

yes you can add a better cam but if you go too big of a cam youll have a rough idle and no vaccum so stoping gets to be fun i have had to run a vaccum pump before to have power brakes at low rpm. doesnt matter how fast your car is if you cant stop it

 

Very informative posts... thanks everyone