"The above said, if the valves are not properly adjusted, a 216 or 235 can be a lot noisier than it should be."
When you next plan to adjust the valves, take off the rocker-arm assembly and inspect the surfaces on the tappets that contact the top of the valve stem. They might have wear-indentations in the contact-surface. This produces noise and also results in incorrect valve lash/gap settings (most likely affecting gas mileage and performance?)
These surfaces can be carefully resurfaced/smoothed. If that is needed, you will have excessive noise when the engine is running. (there are other "wear areas" in that assembly (the two "pipes"), but those indentations on the tappets/rocker-arms are the most most common wear areas)
If/when you ever visit northeastern NC, please stop by my house for a ride. You can sit in the rear seat of my Suburban and we will be able to easily talk with each other at 60-65 mph.
