440 wont start

67Dart273 got it.. back off the rocker shaft bolts about a turn, and maybe a little more if it still pops, this'll give you lots of Valve clearance.. then fire it up,,slowly and evenly retighten the rocker shafts while engine is running, as you tighten down the bolts,,the engine will slow.. stop tightening until it picks back up, then tighten a little more.. if you do it too fast ,, it will kill the engine, and not give the lifter time to bleed down to proper size, .. what is likely happening is valves aren't closing all the way, cuz the lifters pumped-up.. is quick easy fix.. watch out for spraying oil on exhaust manifolds.. I put soaking wet shop towels on em.. .. sounds complicated, but is easy after the first dozens times.. lol

Happened often after planing heads, or changing over to steel head gskts from composite, at times was nec to shim up shafts, or preferably shorten pushrods, but that was before adjustable pushrods..

Oh, and by the way, the dipstick makes an excellent tool to hold the pushrods up as you put rocker shafts on.. just lay dipstick across the top of all the rocker stands, pushrods above it.....