It's a friend's 67 C30 with a carb'd 350 in it. I just got done putting plugs, filters, and a performer intake on it. After setting the points, my son and I set the timing. What we found was that where it would rev without stumbling on throttle snap, it wouldn't start. Where we could get it to start easily, there was a huge stumble, almost to the point of dying when you snapped the throttle open. We compromised on the timing to minimize the stumble but still start. After going out in the woods yesterday for our first load of firewood of the year, I noticed that when the engine is hot, it doesn't want to crank easily, like the timing is still to far advanced. If I change the timing a little more, what can be done about the stumble on throttle snap? It is completely stock except for the manifold.