318 For Fun

How much hp you after?

Seem like you want the best idle to 4500 rpm maybe 5000 rpm max powerband. Right ?

Idle to 2500 rpm is hard to improve over stock. Lower pumping loss, friction, efficiency like Cr can help but overall best you can hope for is least loss or little gain while trying to gain in the 2500-5000 range which shouldn't be to hard, cam choice would be the biggest factor. Hp is torque over time (rpm) and torque is mainly a product of displacement so the easiest way to gain in a fixed powerband is displacement either Naturally aspirated and or artificial like blower, turbo. Even rpm is a form of displacement, you Rev 10% more you displace 10% ish more air.

As for velocity, to make power you need to increase air flow 'cfm' and efficiency best you can do on that front is bump Cr, as for air flow exhaust and dual plane 4bbl are a given and generally no downside. Which leaves heads and cam, modern hemi an LS engines use head flow with mild cams to get streetable power, restrictive heads with bigger cams for same power is a less street friendly way.

So say your looking to make 1 hp per Cid which is a healthy but streetable engine if done the right way. So say your cam gonna be a mild 210 @ 0.050' .475-.500' lift 110-114 you need a head that will flow enough to make 325 hp with that cam, a stock 318 head wouldn't magnum should, speedmaster easily. Not saying velocity ain't important but people over worry about. In a full throttle run you spend little time under 2500 rpm, driving at speed needs very little hp, so it only under light to mid acceleration could be a problem, I'd say it would be worse with restrictive heads and bigger cam, if you go with gears in a light car a mild stall even less of an issue. Were not talking fully ported W2 here.