[sigshooter]

timing and todays poor grade of fuel will give you a clatter under a load. Set the timing and try a higher octane fuel or some fuel additive. How old is your fuel in the tank? if it has been sitting a few months while your engine build was going on it could have starting loosing its kick. Todays fuels aren't meant to be stored for very long.

We live in a fast paced world now where Autos get driven more in a day than they would in a week when our trucks were new. They don't plan on fuel sitting in tanks, plus all the good stuff is bad for the enviroment .... no more lead = no more valves