Bill; where in N.Y. are you? Nevermind. I did a mapqest search. Lynbrook. If worse comes to worse, I know a excellent mech. in Huntington on MainSt. (Rt.110) near Rt. 25A
I doubt a small rad will have caused this problem. How many miles on the engine? The lifter could be getting sticky. But since new.... could be a bad lifter of a lifter bore to small/out of round.
Hydrolic lifters ... should there be an adj? - as I mentioned, I am no engine builder.
Hyd. lifters do not have any adjustment for you to do. There self adjusting. There should be a certain amount of preload or amount of depresion on the top from the pushrod. Thats it.
As you mentioned, your no engine builder. You need not be one to make some simple adjustments or changes to the engine. If your a rookie/novice to engines, we can point the way and explain, but nows the time to ethier pay the mech. to fix it or get dirty and try yourself. Remember, we were all there once.