HORSEPOWER: MYTHS AND FACTS

Camshaft

Myth:

Installing a Hotter cam in a stock engine will always get you more horsepower.

Fact:

Often times this hinders the performance of the vehicle when going with a very aggressive profile. Without changing anything else within the engine there may be little to no gain.

A bigger camshaft should be complimented with better flowing cylinder Heads, valvetrain, more efficient Induction intake,  air / fuel system, Exhaust, compression ect. An engine is a big Air pump, the faster it takes air in and expels it out the more efficient it's going to be.  When the rest of the engine is choked for air it can only go so far.  A mild cam upgrade can help get a little more torque and horses just don't expect a huge gain unless the other pieces of the puzzle are factored in.

Cylinder Heads

Myth:

Installing a Cylinder Head with Big Valves and Runners will get more power.

Fact:

This may be true when dealing with an engine that has bigger cubic inches,  more compression, a large intake manifold, carb or injectors.

The power band of the motor changes as well, The engine may not start gaining power until 4000+ RPMs, below that it will be lazy.

The engine packages we offer are intended to be used mostly for the street, so get instant throttle response from your vehicle the runner and valve sizes

need to match the cubic inch size of the motor .  Typically a 302 motor we'll go with a 170-180cc runner size along with a 1.94 valve size.  When going with a 427w we will be inclined to use a 2.05 valve size along with a 210-225 runner size.

Big Block Vs. Small Block

Myth:

A Big block engine will outperform a HO Small block Ford Engine.

Fact:

True but most of the time not as practical as going with a stroker small block engine.

The small block is approx. 200lbs. lighter, more efficient on gas, fits more easily and HP and Torque aren't far from each other.

When comparing a 500HP small block and Big Block engine. The car will handle much better with the weight savings as well. 

Stall Speed

Myth:

Torque converters with high stall speeds will get your engine to rev faster.

Fact:

This depends upon your engine and vehicle.  HP and Torque of the engine, Weight, use of vehicle are all factors that come into play. We suggest speaking with a

transmission specialist on this. When faced between a smaller or higher stall speed Torque converter we suggest being more conservative.  Going to high of a stall speed

can be detrimental to the off the line performance of your vehicle.

Peak Torque vs Peak HP Ratings

Myth:

You need a lot of Horsepower to get a lot of Torque.

Fact:

There are two basic components to engine power. One is torque -- the amount of twisting force the pistons and connecting rods exert on the crank shaft. This is the force that gets the car moving.

The other is horsepower -- torque applied over time.

The equation for calculating horsepower from torque and rpm is:

HP = Torque x rpm
___________5252

where HP is horsepower, RPM is the specific RPM you're looking at, and 5252 is a constant that comes from the derivation of the equation.

Ideally, an engine's torque curve would be flat -- You get the same amount of torque whether the engine is idling or running at full throttle. In fact, this doesn't happen. There are many factors, from the engine's bore and stroke, breathing characteristics and cam timing to intake and exhaust tuning and possibly phases of the moon all affect torque at various rpm.

The result is a torque curve . Because horsepower is directly related to engine rpm and torque, the horsepower curve reflects the torque.

A "broad power band" would come from a flat torque curve. You get useful torque and a steady increase of power over a wide rpm range. A car with such an engine feels like you can put your foot down at any rpm and get power. It would be easy to drive at all speeds.

A "peaky" engine" is the opposite -- an engine's torque curve is much better at one narrow rpm range than at others. More to the point, this happens at the high end of the rpm range. This kind of car would feel "gutless" in the low to mid rpm range. Then it comes on with a bang when you get into the fat part of the torque curve. You would be shifting gears frequently to stay in the power band and have a tendency to bog down or stall the engine if you're not careful with the clutch.

Next question: What makes an engine "torquey" or "peaky?"

Torque comes from a long stroke and relatively small cylinder bores; this is called an "under-square" engine. As you know, the longer a lever arm you have, the more torque you can generate. The drawback of a long stroke/small bore engine isStreet Performance at FordCobraEngines.com that it can't rev very fast. Imagine trying to turn a three foot long crank, for example. The valve timing tends to be short, with little overlap between intake and exhaust, and there isn't all that much attention paid to intake and exhaust breathing.

Peak horsepower comes from the opposite characteristics: The cylinder bore diameters are larger than the stroke is long -- a condition called "over-square." In Formula One engines, they are very oversquare, with the bore 40% or more larger than stroke length. The cam shafts have high lift to allow a lot of air to flow into the engine. They also have considerable overlap, when both intake and exhaust valves are open, to allow cross-flow -- the exhaust gas leaving the cylinder creates a vacuum that draws the intake into the cylinder.


The over-all effect is an engine that produces prodigious power, thanks to its ability to turn at high rpm, but does not have all that much torque. That's good for running at high speed, but not so hot for accelleration.  The trick here is not keeping the rpm up, but not lighting the tires every time you push the accelerator!

Our engine packages have an excellent Torque to Hp ratio for a street performance car.

Question:

I just installed a new engine in my car but it feels like there isn't enough power..

Answer:

This can be a number of things. The rest of the car needs to be setup to accommodate the extra Horsepower and Torque.  IE. Rear End,  Torque Converter or Clutch, Headers, Tires, Brakes, suspension ect.  Your only as strong as your weakest link.

Definition The term horsepower was invented by the engineer James Watt. Watt lived from 1736 to 1819 and is most famous for his work on improving the performance of steam engines. We are also reminded of him every day when we talk about 60-watt light bulbs. What horsepower means is this: In Watt's judgement, one horse can do 33,000 foot-pounds of work every minute. So, imagine a horse raising coal out of a coal mine as shown above. A horse exerting 1 horsepower can raise 330 pounds of coal 100 feet in a minute, or 33 pounds of coal 1,000 feet in one minute, or 1,000 pounds 33 feet in one minute. You can make up whatever combination of feet and pounds you like. As long as the product is 33,000 foot-pounds in one minute, you have a horsepower.       If you want to know the horsepower of an engine, you hook the engine up to a dynamometer. A dynamometer places a load on the engine and measures the amount of power that the engine can produce against the load. Torque Imagine that you have a big socket wrench with a 2-foot-long handle on it, and you apply 50 pounds of force to that 2-foot handle. What you are doing is applying a torque, or turning force, of 100 pound-feet (50 pounds to a 2-foot-long handle) to the bolt. You could get the same 100 pound-feet of torque by applying 1 pound of force to the end of a 100-foot handle or 100 pounds of force to a 1-foot handle. Similarly, if you attach a shaft to an engine, the engine can apply torque to the shaft. A dynamometer measures this torque. You can easily convert torque to horsepower by multiplying torque by rpm/5,252. You can get an idea of how a dynamometer works in the following way: Imagine that you turn on a car engine, put it in neutral and floor it. The engine would run so fast it would explode. That's no good, so on a dynamometer you apply a load to the floored engine and measure the load the engine can handle at different engine speeds. You might hook an engine to a dynamometer, floor it and use the dynamometer to apply enough of a load to the engine to keep it at, say, 7,000 rpm. You record how much load the engine can handle. Then you apply additional load to knock the engine speed down to 6,500 rpm and record the load there. Then you apply additional load to get it down to 6,000 rpm, and so on. You can do the same thing starting down at 500 or 1,000 rpm and working your way up. What dynamometers actually measure is torque (in pound-feet), and to convert torque to horsepower you simply multiply torque by rpm /5,252. If you plot the horsepower versus the rpm values for the engine, what you end up with is a horsepower curve for the engine. A typical horsepower curve for a high-performance engine might look like this. What a graph like this points out is that any engine has a peak horsepower -- an rpm value at which the power available from the engine is at its maximum. An engine also has a peak torque at a specific rpm. You will often see this expressed in a brochure or a review in a magazine as "320 HP @ 6500 rpm, 290 lb-ft torque @ 5000 rpm" (the figures for the 1999 Shelby Series 1). When people say an engine has "lots of low-end torque," what they mean is that the peak torque occurs at a fairly low rpm value, like 2,000 or 3,000 rpm.    Home page FORD PERFORMANCE ENGINES 1-800-704-5385

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