One of the more controversial areas of cylinder head theory is swirl, but it’s a concept that packs more hype than substance. Swirl proponents say it contributes to a more homogenized air/fuel mixture, which eliminates lean pockets and reduces the potential of detonation. However, Judson isn’t too convinced of its merits. "Experts can’t even agree on how to accurately measure swirl, and every device that measures swirl affects it somehow," he says. "Promoting swirl adversely affects inertia and flow. While it may help with gas mileage, emissions, and to some degree power, optimizing quench is a much more effective method of homogenizing the air/fuel mixture without the adverse effects in airflow associated with swirl." In other words, quench trumps swirl every day of the week.

WHICH MAKES MORE POWER?

Iron vs. Aluminum Heads: Which Make More Power?
"Unless rules require it, you don’t want to run an iron head. The only advantage is the lower cost. All this hoopla that heat escapes too quickly out of the chambers with aluminum heads compared to iron heads is pure B.S. If you’re that worried about heat dissipating too quickly, just move the water jacket farther out. How hard is that? Iron is more prone to cracking and much harder to repair; you have a whole lot better chance of salvaging an aluminum head if it’s damaged. You can also port aluminum twice as fast. I remember the days of spitting up black stuff for two full days after porting a set of iron heads. Another major problem with iron is that you can’t weld and add metal to it, which takes away from a skilled porter’s creativity in reshaping ports and combustion chambers. The weight difference isn’t too bad with typical small–block wedge heads, but the penalty is significant with big–block or canted–valve heads, or any time you raise the runners. Some circle–track guys say you need an extra 35 hp on a motor with iron heads just to make up for the additional mass, since the weight is so high up off the ground and so far forward in the chassis."