they should sound like a well oiled sewing machine, if adjusted to be silent you risk valve recession, especially if hardened seats haven't been installed and/or you run it hard .... better a slight 'noise' [as factory designed] than burned valves or seats

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics