DV: Do you have any words of wisdom you care to share in ports?

Judson Massingill: JM: Heck I share everything David, you should know that but these days it is only at a price. Often information you get for nothing is worth about that–nothing. I also warn them that often those who do the most talking are the least knowledgeable.

But there is one thing I'd like to get off my chest. I’ve read in several popular publications comments about having too much cylinder head interfering that a head that flows too much will hurt power. Let me tell you there is no such thing as too much cylinder head in terms of airflow, only too much port cross sectional area or not enough motor under the head. If you could have too much cylinder head the justification for turbos, blowers, and nitrous would take a serious dive.

DV: Feel better now?

JM: Yes-thank you.

DV: Got anything more to say on ports?

JM: Yes, lots more that you have space for. But here’s something worth spending time talking about–the amount of port flow required to get the job done. When I’m talking of ’the job’ I mean achieving a target output from the motor consistent with a respectably wide power band. If there is a target output there will need to be a target head flow. If the head falls below that flow the motor will need more cam to compensate. That means a cammier motor with a narrower power band. If the target flow is exceeded then a shorter cam will allow the target output to be achieved. One of the first things I teach my students is achieving this target flow. Determining what this flow may be depends on the number of inches of cylinder it must supply and the rpm the motor can be turned. The rpm is dependent on the stroke and the number of "Gs" the rods can stand. Good rods–more rpm; stock rods–less.

DV: Do you think the flow bench is the entire answer to port development?

JM: Well there is to my mind little doubt that good flow is indispensable but there is a lot of evidence to support the fact that as the output per cube goes up, port shape plays an increasingly important role. The thousands of hours I have spent on the dyno seems to paint a reasonable, and not unexpected, picture of the situation. If we consider a street motor then–unless you have a real gift for screwing up–more air always means more power. But that unwritten law of diminishing returns slowly but surely starts to come into effect at about 1.5 hp per cube. By the time we get to 2 hp per cube, factors other than cfm seem to play a greater role. For instance, the position of the choke point in relation to the valve, the shape of the short≠side turn, the port’s taper out to the end in the manifold, the radius at the end and so on. You can change one of these factors, see little difference, if any, in flow and get a 20–30 hp change in output. Isolating what these factors are and passing them on to our students has been an ongoing priority.

DV: Let’s talk about the fuel deliver system for a moment, how do you feel about carbs and fuel injection?

JM: I know there are a lot of folks who are not going to want to hear this, but in terms of outright hp, an unrestricted single 4–barrel or a tunnel ram and carbs is hard to beat. However, if you want to put some street manners into a big cammed street motor then for drivability at low speed the injection is the way to go. Now I don’t want to make it seem like there is a huge power difference between the two systems. If we are talking the same manifold design on either fuel injection or carbs then there might be 5–10 hp in the 600– to 700 – hp range. But consider this, our current race carb setups are the result of close to 40 years of intense competition development. With fuel injection there are still dozens of variables to deal with other than regular calibration factors. If Pro Stock ever goes to fuel injection I predict things will move forward in a hurry.