My hydraulic lifters in my 95 Suburban 454 sound like mechanical lifters that need to be adjusted. Engine was rebuilt last year. Valve train has been noisy since. The cam is a Summit SUM-1300. I have replaced the lifters since with a set of Comp Cams lifters. Same noise. They are adjusted to 1 1/4 turn past zero lash. Oil pressure warm is 25psi at idle and 45 at cruise. Any Ideas?