CFM - Technical info

There are several types of heads and intake set ups for all types of engines. Choosing the right one for your application can be a tough decision. Here at CFM we believe in helping all that we can. This page will delve into different tech topics concerning engines and cylinder heads. Remember that the information contained in these pages is general. If you have specific questions please feel free to call or E-mail.

 

Info will be posted and updated often

Basic tech

A look at producing power through air flow

When most people think about additional airflow they think about the heads alone. Airflow needs to be looked at as a total package. How is the air going to get from one end of the engine to the other. This would include looking at everything from the air cleaner to the tail pipes.

When choosing a direction to take, many deciding factors should be considered.

Where would I like my engine to make power?

How much power would I like it to make?

What will be the primary purpose of the vehicle?

Will I be using a power adder?

Is streetability even a concern?

Only after you have laid a basic outline of what you wish to accomplish, can you advance to the next phase.

Choosing components

It is very important to match components so that they work harmoniously. It will do no good to run racing heads with stock intake and exhaust manifolds. Matching of components has become easier than ever with the dyno proven slew of available crate engines and power packages.

Don't be afraid to ask questions of those who may have a running combination similar to the one you would like to build. They have already done the ground work, you might as well reap the benefits of their labor.

Most components are generally rated for a specific RPM range or engine size. Recommendations for parts such as intakes, carbs, cams, ect can be provided by their manufacturers or a reputable engine shop.

The camshaft is the key to good useable power

Choose a camshaft with your head and not your pride. All too often a hotrodder can get carried away with lift and duration figures. It's not always the biggest cam that will be the best for the particular situation. When choosing a camshaft it is better to be conservative than overzealous.

 

Advanced tech

useable power

Ever have a buddy with a high HP engine that never quite ran as well as it should?

Many times peak horsepower numbers can confuse an eager racer. In most forms of racing, acceleration will play a very key role. Drag Racing's primary objective is, in it's self, an acceleration contest . Peak power does not do a very good job of accelerating a vehicle alone. It takes the entire power curve of the engine to do this. Too many racers get caught up in the peak power issue.

Let's say you had two engines in the same car. One engine made 800 HP at peak, but only averaged 450 HP through the intended RPM range. The other engine peaked at 700 HP, but averaged 500 HP through the intended RPM range.

Which one do you think would accelerate more quickly?

Average power will almost always prevail. The same theory applies to airflow. Big peak airflow numbers are meaningless if not accompanied by good average flow numbers. When a camshaft opens a valve to full lift it will see that number one time during the cycle. Every number below max lift will be seen twice in the same cycle. It is these numbers that are seen twice that should be the biggest concern to a head porter, engine builder, and racer. Good average flow will make even a mediocre engine come to life. If you break down what an internal combustion engine actually does it gets quite simple. All it really does is pump air and fuel in and out of itself. Hence, the more air and fuel you can pump through it, the more power it should make.

Valve angle and placement

There are three major types of cylinder head design, Wedge, Canted, and Hemishperical. There are many types of each variation which alter the angles, placement, and shape of the valves.

 The Wedge type places the valves inline along the bore of the engine. Some examples are Chevy, Ford, and Chrysler small blocks.

The Canted valve type places the valves at a cant, or angle away from each other and the walls of the cylinder bore. A perfect example of this is the big block Chevy.

The Hemishperical or "Hemi" type is well know to most of us. It places the valves in a half sphere shaped chamber perpandicular to the bores centerline. Both Chrysler and Ford offered such and arrangement. The "Hemi" design is widely used in professional drag racing for many of the top classes.

You may often hear about altered valve angle heads. This is most commonly done to unshroud, or move the valves away from the cylinder bore wall. It also allows for some rotation of the port to give a better line of site to the valve and cylinder.

 

More to come