Racing Cam Basics - An Introduction To Camshafts

Cams that have big lifts and long durations are not just hard on the valvetrain, but they require a good bit of power just to function. If the heads and intake system cannot handle or fully utilize a high lift and long duration cam, then why use it? It is all about matching the components to make the engine work as well as possible and maximize performance.

The data will really drive you to making the selection on the cam you need. These are just the start of the questions you need to ask to make an intelligent cam selection:

What rpm will the engine be running, or what rpm do you want the engine to run?

- What power characteristics do you want from the engine?
- This will be dependent on the track you will be racing. Include factors such as:
* Low speed torque
* Midrange
* High rpm power

We are in the most advantageous time period to be a racer. Many of the cam sellers have hot lines that will help you to make the correct cam choice for your application. Armed with the right questions, you can get professional help making the decision on the cam you will be using for your particular application. The cam can and will have a very large effect on the power curve your engine will develop. You have to be careful that you do not end up building power over a very narrow range. This can have the effect of making the engine "pipey," a condition usually associated with two stroke engines, and one that will lead to very abrupt power delivery usually not conducive to smooth driving and fast laps.

Noted engine builder Billy Smith, of RPM Engine Development in Chandler, Arizona, has some great advice about cam selection. His words echoed McCarver, but he also adds some other interesting comments.

"It is important to understand the skill level and experience of the driver when making a cam selection," says Smith. "New drivers need power delivery to be smoother and less abrupt. This is especially important on dirt tracks and very tight asphalt tracks where the power delivery can upset the car and cause some real problems getting and keeping the car hooked up to the track."

Power characteristics are just as important as peak power and torque numbers. This is an area that you have complete control over.

Something else you need to remember: If you have a highly developed engine, just changing the cam is not going to net big gains in power. If you are running a Dirt Late Model with an engine making over 700hp, for example, changing the cam is not going to net a 100hp gain. The same can be said for engines in the lower power ranges. Engine building is about making the right decisions and integrating all of the parts together to develop a well rounded package where you are balancing power, durability, drivability, and budget.

From a tuning perspective, you can make a cam selection that will allow you to further optimize your engine package at a later date. You may be able to tune with rocker arms with different ratios to adjust your engine to a specific track and make your engine dollars go that much further. You may want to try running different ratio rocker arms on the exhaust side of the engine. Oftentimes it is possible to change the power characteristic by using a rocker arm on the intake to increase the lift of the intake over the exhaust. Or you may want to use a rocker with a smaller ratio on the exhaust to lessen the amount of lift.