300 HP out of a 318, is it possible with bolt ons?
Hot Rod magazine built a 400 horse teen (supposedly) with zero deck pistons, a 230°/.512 Comp Cam The lift was using Magnum heads and their 1.6 ratio rockers. Intake was a MP open plenum with a 750 Demon etc, etc. Here's a link. I think a zero deck Teen with some mildly massaged Speedmaster heads and the right cam could get to 400 horse easily.
https://www.motortrend.com/how-to/mopp-0409-318-engine-build/
But the 400HP 318 was measured using magazine horse power. That's different, dontchya know? lol
in 2007 built exactly this motor, to the T, from the article and can confirm that it puts down 400hp. i did not spray it with laughing gas, though.
in fact, it was so nice i built it twice. i sold the car the motor was in so i built another one to put into my other, other dart. on the chassis dyno something went wrong as i went for power pulls. either a valve guide was too tight and hung an intake and it and the piston had a logistics problem or two of my push rods were too short resulting in an unplanned meeting in the cylinder.
so, off came the heads. miraculously the piston was undamaged. cracked two valve guides and bent two valves. yay. so i upped the ante and went for the RT heads and threw some harland sharp roller rockers at it while everything was apart. the single plane was fun times, but with the light weight aluminum flywheel and race clutch it was damn near undriveable in traffic, so i replaced the M1 with a performer RPM. i lost a bit on the top end, but torque and street manners were way, way better.
i was working at a dyno shop at the time. i bought all my own parts, nobody was sponsoring me and there was no outside influence. old school clayton water brake dyno, chassis dyno was in floor dual roller. there was no finger on the scale, the number was the number.
i don't know if i have any of the paperwork-- a lot of it went with the car, and my personal stuff i've moved about 5 times, so i don't have the granular numbers to the 1/4hp & tq but i can tell you it ran the damn number.
here's the car too:
1965 Dodge Dart F/S