340 cam in a 318

The 318 is not a huge engine. That is why cam selection requires careful thought, with respect to the rest of the combo such as diff ratio, weight, etc. Easy to convert it to canine status....
It is not like a stock 454 Chev where a bigger cam is going to automatically add more HP. As you increase cam duration, you reach a point where instead of HP increasing throughout the rpm range, you are just shifting the power, ie, power is depleted from the low end & added to the top end.