There is a lot to cam profiles . The numbers at .050are just part of the story. I have a 210 degree @ .050 exhaust lobe that has the same .200 numbers as the 218 lobe. I use it where we are trying to fit a bigger cam in a tight clearance motor. The Duramax has considerable more rocker ratio on the exhaust then the intake. The correct Ratio is 1.34 Intake and 1.64 on the exhaust .
I hear a lot about LSA ( Lobe separation Angle ). This number and ILC ( Intake Lobe Center line) are number often used for the novice cam buyer to get an idea of the specs on a cam but really have no use to an advanced engine builder The only proper way to look at cam profiles , is to look at each events numbers individually . IE Open of exhaust , Close of Exhaust, Open of the Intake and close of the intake.
When you are chasing power, and doing engine development, you should only change one of those numbers at a time. For instance, if you have a small cam profile like a 205 210 110 installed in at 100 ILC that works well. This cam spools the chargers well, and runs good but will hit the wall around 4500 rpms. The smart move is to let the intake valve stay open longed to catch a little more air. This profile,closes the intake valve at 22.5 degrees ABDC meaning the pistons is 22.5 degrees coming back up the bore, lets add 10 more degrees. The intake is now closing at 32.5 degrees ABDC. This 10 degrees is a good amount , and will move the upper RPM up by about 500 rpms , It will starting getting a little softer around 2000 rpms , but not much. Nowthe ILC it has now changed to 105 and LSA has changed to 112.5 so the cam spec are now 215 210 112.5 installed in at 105 .
Why only changed one number. You have to make little steps , and keep an open mind I hear the Cummins guys say that only one LSA works in a Cummins 108 . This is just lack of real knowledge of how this all work. I some times believe that when you buy a Duramax its like changing from a blond to a brunette
I have done cams as big at 240 210 116 , these are extreme and will lose lots of power down low , but make incredible power in a narrow power band up high.
as in any part of a development program you will eventually grind a fence post , but you have to go there to know where the end is at. Then years latter like in the Pro Stock cams what we once thought was not right comes back around.
There are people that bolts parts in and expect to run as fast or make as much power as the guy that beats on his stuff and tinkers . You get power buy working on it .
