Keep in mind that because the valve lift in diesel engines isn’t very high, we know the biggest differences will be that the diesel cylinder head is producing more swirl and doing it faster. Now in a diesel cylinder head, the swirl from the intake port entering the combustion chamber can be as much as three times the rpm of gasoline cylinder heads. This generally takes place from approximately. In a typical small block Chevy, swirl ranges anywhere from 700 to 1,400 rpm, in accordance with how much lift is measured at the valve. Air tends to flow better with less bends and restrictions On a flow bench, swirl is measured with a swirl meter which will, in turn, be measured in rpm. This happens because you are reshaping the port’s design for more airflow and most of the time the head porter is trying to straighten the port. On the flow bench you will often see that porting cylinder heads for more cfm causes the swirl percentage to drop. There are different levels of swirl found in gasoline engines depending on whether it is a stock, mild or more wild application. we take what you just said, re-do it using what I like to call "the right way" and see where we end up? Man, since port swirl and flow doesn't play any role of significance in a forced induction app, think of the $3500 i wasted in porting and head work that I could've done myself in my garage with a few carbides. once you take off too much you can never put it back. remember to go slow and check your work often. this way you can get them all close and then measure them for the final touches. this way you kinda get a feel for what it looks like visually. another suggestion is to do all the intake ports at one time and the same with the exhaust. sanding stones did not work very good at all. for tooling, several size and shaped carbide burrs seem to work the best with various sand rolls to smooth it all out. port size is important and I would recommend measuring them as you go until you have done a few. the valve guide area can cause shrouding due to the sharp edges and overhang. but if you do get into this "less dense" material it can allow moisture to seep through into the intake and exhaust runners. the swirling is not really that important as the application is forced induction and the fuel is injected directly into the cylinder. The real worry on a 7.3L head is that removing too much material can get into areas of more porous metal.
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