to clear off whether valves are hitting piston top.
what pistons are you using?
what's the cams lift?
you're rotating camshaft with heads on
and valve spring pressure?
i've never done that.
sounds kind of hard.
i know 283 but not 305 heads.
let me see, smaller chamber equals
valve closer to head or not?
is this a fresh engine or problem just start?
have a nice day!