Don is right on target about the hydraulic lifters leaking down in a stovebolt! After two years of having my newly overhauled 235 six lifters leaking down-especially in during the Winter months- I installed solid lifters and had no more problems. Sure the solids are a little more noisy but that's how a 62 Chevy truck is suspose to sound. I swapped the lifters after consulting the experts there at Stovebolt.com and boy do they know their business!