I've noticed that many cams for the 235, including some OEM, feature longer exhaust duration. The bias ranges from a few degrees to 12 or so longer.
In general, intake ports are sensitive to increased lift, either by lobe height or rocker arm ratio, but exhaust ports are more sensitive to the crank position where the exhaust valve cracks open (in degrees BBDC).
This is partially due to much higher pressure at the exhaust valve (up to 70 psi), which quickly vents the cylinder once the valve opens, while the intake port pressure may not rise above 3.5 psi even with a tuned exhaust system.
The stock cam in the 216 is dual pattern grind. I am running a regrind based on an ancient Isky specification (DP#2)
Inliners Post circa '04Isky advertised it as a 250/280 affair.
Stock spec is 220/231.
I asked the guys at Delta to regrind a cam to the Isky DP#2 spec. The cam doctor report for the stick indicates:
248/264 @ .020
205/233 @ .050
Theoretical Lift is .41/.40 with stock 1.5:1 rockers. Add lash & rocker retreat - it's more like .39x.
