Maximum Horsepower


What you do:

Choose carburetor or throttle body sizes, intake runner diameter, intake valve lift, intake valve duration, intake valve size, bore and stroke to produce maximum horsepower at the rpm you want.


Factors to consider:

1. Carburetor or throttle body size, intake runner diameter, intake valve lift, intake valve duration, intake valve size, bore and stroke all control air velocity. Air velocity is limited to the speed of sound, which is 767.58 mph (miles per hour) or 67547.4 fpm (feet per minute).

Small carburetor or throttle body size, intake runner diameter, intake valve lift, intake valve duration, or intake valve size all cause air to move faster and reach the speed of sound at a lower rpm. This is good if you want your power to come in early and you want big torque. Larger bore and stroke do the same thing, since each stroke of the piston draws more air.

Large carburetor or throttle body size, intake runner diameter, intake valve lift, intake valve duration, or intake valve size all cause the air to move slower and reach the speed of sound at a higher rpm. This is good if you want your power to come in at higher rpms. Large diameters and lifts allow the engine to breath, increasing maximum horsepower at the cost of the power coming in later.

Small bore and stroke allow for a high revving engine. It is possible for the small bore and stroke engine to draw as much air as a large bore and stroke engine, but the air will be drawn through at much higher rpms.

2. Turbo chargers and super chargers increase maximum horsepower and torque. They force more air in to the engine, which increases air density. Higher air density allows more fuel to be added, which increases power.

3. Maximum horsepower will often occur before maximum rpm. Most car engines are designed this way so that when the car shifts to a higher gear the engine drops to an rpm that still puts out a lot of horsepower.

4. If your maximum horsepower is 0, the most likely causes are:
1. The total of your intake plus exhaust valve diameters is greater than the bore. This means one of the valves is hitting the deck of the block, so it can't open.
2. You do not have a carburetor or throttle body (meaning you set both to 0).
3. One of the air passages is set to 0 (like intake or exhaust valve settings).