Picking the Right Headers

Picking the Right Headers
By Don Terrill (c) - www.RacingSecrets.com

Choosing the right Headers has as much to do with making more power as it does with where that power happens - at what RPM.

What needs to be decided and in what order:

1. Primary Diameter
2. Collector Diameter
3. Primary Length

Questions that need to be answered:

1. Engine Size - More cubic inches = more cfm required.
   
2. RPM - More rpm = more cfm required.
3. Application - For your type of racing, where do you want the power band?

Power Band Tuning: (general rules)

1. Larger primary diameter moves power band up, smaller down.
2. Larger collector diameter moves power band up, smaller down.
3. Longer primary length moves power band down, shorter up.
   

Industry Myth: You must have equal length primaries. This myth has been around for decades and is alive and well today. One of the major goals of equal length headers is to equally space exhaust pulses at the collector. The problem is the engine firing order is not taken into account. Let's look at the small block chevy.

Chevy Firing Order: 18436572
Gap between firings = 90',90',90',90',90',90',90' Crank Rotation

Now let's look at how the driver's side header sees the pulses.

Driver's Header Firing Order: 1357
Gap between firings = 270',180',90',180' Crank Rotation

Do you see the problem?

Do you still think every application needs equal length Headers?

Biggest header mistake: Leaky Header Gaskets - it's not just annoying, it can kill a noticeable amount of power.

Want to send off a nasty email about how wrong I am? Well, first read this and then write your own article.