Sounds like what you are describing are shims below the valve spring that may have been used to set the correct closed-valve spring height/tension after the valve seats were recessed some time in the past. The shims may or may not be all the same thickness. Check for correct spring height... that should correct the loose caps if the springs are the correct free length, as they should have a minimum closed tension of 55lb, +/-, higher for newer 235s and 261s. This table may help, from Pre '68 Dave's blog: Valve Spring Pressures and Installed Heights.

Last edited by drdoug; 05/14/2020 6:33 PM.
1947 2nd-Series GMC FC152 3/4-ton
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1953 Chevy Bel Air Sport Coupe Powerglide