65 170 lifter question



I am new to this site and also new to in-line six's.
I just bought a 641/2 vert mustang with a rebuilt 170 (but sat for 3 yrs after rebuid) and it wasn't running good so I took valve covers off and saw about 2/3 of the pushrods bent from stuck tarnished valves. I took the head off and cleaned all the stuck intake valves and bought new pushrods, gaskets and such. 3 of the lifters had the top clips off of them so I took them out. In order to put the clip back on I let out the oil in the 3 lifters. I read a article on hydralic lifters saying it wasn't necessary to load the lifters with oil, infact it said it was better not to so you can set the lifter in the center position and that they would fill with oil after running. Well after putting the engine back together it fired right up, runs good but I can here the lifter clapping noise in the area of the 3 lifters in question.

Does anyone have any info on this... does it take awhile for the lifter to fill up on its own or was the info I got wrong?

Thanks and glad to find a nice site on in-line six's