The Stovebolt Site Forums The Shop Area Engine Shop 216 problem

If they have checked these things-weak breaker arm spring, breaker points improperly adjusted, wrong type of spark plugs- and everything is as you have aid, it can be nothing else but a weak valve spring. Did they check the "new"(?) valve springs before installing them? Sometimes ven new ones are weak. What cam is in it? May need to double spring it for a high-lift cam. But I will guarantee that it is the spring. That is all that will give these symptoms.