Supercharger vs. N/A build!

[olddog]

500 / 302 = 1.66 hp/ci That is difficult to do NA

500 / 347 = 1.44 hp/ci

My rule of thumb is 1.3 hp/ci is about as much a you can build, without going expensive parts and having a high strung peaky engine that is no fun to drive. From my rule of thumb 450 hp out of a 347 or 390 hp out of a 302 is about as much as practical, as you can get to NA.

A 302 can get to 500 hp NA, but not on a moderate budget. To get there the only part out of your existing engine you can use is the block, and I would recommend against using it. If you haven’t heard, the 5.0 block cracks between the main bearing and cam bearing oil galleries. There are pictures around, where the block split completely into two pieces. It’s partly Hp and it is partly rpm. As you go above 400 hp, the odds your block will split get worse, and the higher you go, the more rapidly your odds get worse.

Supercharged:
2 hp/ci is fairly attainable. A supercharged engine can be quite mild mannered, depending on how you build it. Again I wouldn't recommend any parts out of your current engine.

Not all superchargers are the same. Positive displacement blowers (lobbed or roots style and twin screw compressors) give you a very flat torque curve. Non-positive displacement blowers (turbine or fans) make pressure based of tip speed of the fins. Thus at low rpm they build, almost, no pressure. The torque curve goes up at about a 45 degree angle, in my opinion, making the engine useless for anything other than drag racing, and bragging. Others disagree.

Blowers can be used with a carb, but I wouldn’t do it. Sitting a carb on top of a roots blower (on the suction side) works, if you don’t mind it sticking up out of your hood. Putting a pan around the carb and pressuring it works, but then you have to vary the fuel pressure to match the pressure in the carb. This setup does not tolerate sudden throttle changes well, if the boost is high. In my opinion, EFI solves a bunch of problems and makes it much easier. Getting the timing and fuel right under boost is critical and an EFI computer makes it easy. Boosted engines act like a grenade, when the fuel or timing is off for a very short time. The higher the boost, the shorter the time and the less forgiving, on how far you can be off.

You might start by explaining what you want to do with this engine and how did you come to a 500 hp goal. Getting that type of power out of your 302 is not very realistic.