I work for one of the major diesel engine manufacturers, and used to be involved in cylinder head testing. We played around with many different port designs on the flow bench, and one thing that was always of major importance was the swirl dams that were cast into the bottom of the bowl on the intake ports. Although detremental in naturally aspirated gasoline engines, swirl is very important to diesel engiens, in order to achieve even and efficient combustion in the bowl area of the piston. I can't remember if the Cummins had a swirl dam in it, but most of the other manufacturers did. The company I worked for had different heads with different swirl rates, depending on the engine application. These swirl rates were used in different horsepower applications. I would be curious if Cummins does the same thing? Also, when we did any work on the ports, we were always very careful when working around the swirl dams. In fact, 2 different heads would produce 2 different swirl numbers, due to casting variations. Although increasing the flow of the ports is important in gaining additional power, my experience in head flow is that swirl is also of great importance, and that by just porting out the head to a larger size, it is possible to cause a decrease in swirl, which is detremental to engine performance. It all depends on if the swirl dams are disturbed in the porting process, and if the port becomes overly large then some of the airflow is not directed through the swirl dam area. This fact may have already been looked into by those who have ported the Cummins B head, but I had never seen any info on it posted here yet. Just thought I would add a little insight from my experiences. I would be curious to see what kind of improvements the ported heads would make.
Attention: TDR Forum Junkies 
