Originally Posted by curtis73
As a general rule, "bigger" parts means bigger HP, but it means it shifts the power up in the RPMs. Bigger cam, head ports, compression, carb, intake, etc... it all has to be matched. The nice thing about bigger engines is that you can get that bigger power without shifting things up in RPM.
A stock TBI engine (which is what I assume you have) has the tiniest of everything; tiny cam, heads, TBI (carb), and tiny displacement. They were done that way basically so the vehicle had a means of moving around; not much power, but great on emissions and MPG.
When we talk about upgrading an engine for more power or torque, we are basically banking on the fact that the factory made very mild engines. We can put some slightly "bigger" parts on it and get nice power upgrades without putting the power too high in the RPMs. Factory engines typically use parts that make it suited for low power from idle to 4500 rpms. Street engines use head, cam, intake, and carbs designed for 1000-6000 rpms. Race engines use bigger parts and usually don't make power until the 3000-7000 area. The ticket is choosing the right "bigger" parts so that you match the target use with your desires.
On the street, size is king, so a 350 will be much easier to get your power goals without revving to the sky to get it. Then you fine tune it depending on your use. A performance truck that sometimes tows a boat? You're going to want to keep it on the mild side of that 1000-6000 rpm range. A light-weight Camaro that only gets driven on the street on the weekends? You can get away with a lot more.
The other thing to think about is the rest of the vehicle. You can modify a stock engine a little bit without changing the rest of the vehicle, but keep in mind that torque converter stall, transmission gearing (and strength), rear axle ratio, tire size, traction, rear axle strength, and a whole host of other things come into play. For instance, in that truck, chances are it has a monster rear axle with 4.10 gears already, but the Nova might have a wimpy 7.5" rear axle with 2.73 gears. The more power you add, the more you have to modify the rest of the car to match it.
But... most mild street performance can be dropped in place of a factory wheezer without too much modification.