Port and Air Flow in practice and in theory

This the best practical video I've seen on this subject for quite some time. I'd call this a very light porting job. That's safest if you don't know how thin the metal is in different places, but a way around that is to get a metal ultrasound tool and find out where it's thin, so you can do a more aggressive job.

Personally, I'd remove more in the combustion chamber. Get rid of those machinist ridges more. Sure, it's a small compression loss, but you're probably getting the cylinder head shaved anyway, right?

It takes a lot more skill, but if all you're going to do is a slight smoothing of the port, why scribe for the gasket? Sure, you don't want to go beyond the gasket line, but my point is, matching better to the gasket is a tougher way to go, but an industry standard for a more aggressive porting job.

Could be more like a stage 2 to do that.

If you go bigger, you have to use T tools to measure the inside and make sure those ports are matched.

I bet they weren't matched at the factory! According to headbytes, the more points of measurement to have them even, they higher the stage, more so than how much material is removed. Kind of a balanced way of looking at the stages. Please understand, this is not slander, there is a lot of evidence stacked up on YouTube and many websites, which mention that headbytes of YouTube isn't in good business practices. I learned a lot from him. His engine knowledge isn't perfect, but it's among the best. I've learned a lot from this artist. Some artists don't make good businessmen. Maybe he has a lot of personal issues that have prevented him from keeping up with his promises in porting engines, but a lot of people have lost money and they aren't getting their sometimes rare and original parts back that belong on their classic rides.

Lets get back to something prettier.

More flow, smoother flow. These are common concepts. People sometimes worry about losing torque at lower RPM because making ports larger, while it can increase flow (it can lose flow as well if you do it wrong), it also lowers the air velocity in your ports, which is more needed at lower RPM. Know though, that people porting for racing aren't worried about a little loss down low when they're getting better flow bouncing off of red line and back up to it with each gear shift.

So while I'm working toward a cylinder head project of my own, I probably shouldn't open the ports up much as the automatic transmission keeps my RPM low most of the time. This would cost me power, even if on the on ramp to the freeway the higher possible RPM, which won't ever happen in the city, lets me have more power there, the car would be less driveable in every other way...at least that's how the theory goes. I so want to put this in practice! I still don't have the electric die grinder or bigger air compressor which I need.

In the video above they talked a little about how to get swirl, but this was one of the video's down falls as I don't think the technique they're talking about would actually create more swirl. To learn more about that, go from watching the practical example above to my theory video below.



Source: Port and Airflow Theory, PolyQuad cylinder chambers, Creating Swirl by DENichols

When it comes to swirl, on single valve intakes you need a different technique than you do in dual overhead cams or DOHC.

David Vizard's concept in the video above is to make one of the vales larger, support that valve with more porting. The idea is to make for more flow on one valve so that as it's great velocity air goes into the chamber, it causes a swirl. Swirl also squeezes more air into the combustion chamber. Swirls prevent fuel molecules from colliding as much. Turbulent air, like what is shown to be reduced in the first more practical example video above makes fuel droplets collide more, which makes them less atomized and less burnable.

By AutoBravado