"61"- - - -as in "1961" I assume? That's the next-to-last year of production for a 235, assuming it's got an original engine in it. All the car engines from the late 50's, and, I believe, the late-model truck 235's had hydraulic lifters. Hydraulics are supposed to be virtually silent when they're adjusted properly, but lots of factors can influence the noise level, including how much wear all the parts have.
If you use the search function here for "valve adjustment", you'll find lots of advice on adjusting valves, both mechanical and hydraulic, and at least some of it is correct. There's more misinformation out there about adjusting hydraulic lifters than possibly any other topic up for discussion among stovebolters. I prefer using the "companion cylinder" method of adjustment, with the warmed-up engine stopped, then rotated by hand until each cylinder is in position to be adjusted. I've never found an effective way of doing an engine-running adjustment on hydraulic lifters, but then, I've only been doing it 49 years!
Jerry
