how can i get 400hp out of a 318?
Depending on what the OP wants to do with his 400 hp, a turbo may make perfect sense. Daily driven reliability, the ability to turn the performance up or down, run garbage gas if you need to etc.
400 horsepower is single turbo territory. It does not need to be complicated. I designed & built the system for the SB chebby below in 1978. We used a target motor straight from the dealer, baselined it on the dyno @ 190 hp with a smog legal Quadrajet & 1978 distributor set @ 5 ATDC.
With 6 psi from a single Rajay turbo, we could get 450 ft/lbs all the way to about 4400 rpm - which is 375 hp in anybody's dyno room. Stock smog cam, draw through the OEM Quadrajet. Smog legal components & timing. Easily the worst cast piston made in mexico junk GM ever made. 375 horsepower. Drove like a stock engine unless you opened the secondaries.
It worked well. I still see them for sale on e-bay occasionally 30+ years later like the example below. Making a system for a 318 in an A body would mean making or modifying a passenger side exhaust manifold to mount a properly sized turbo. Really the hardest part of the fabrication comes down to that one manifold.
B.
Depending on what the OP wants to do with his 400 hp, a turbo may make perfect sense. Daily driven reliability, the ability to turn the performance up or down, run garbage gas if you need to etc.
400 horsepower is single turbo territory. It does not need to be complicated. I designed & built the system for the SB chebby below in 1978. We used a target motor straight from the dealer, baselined it on the dyno @ 190 hp with a smog legal Quadrajet & 1978 distributor set @ 5 ATDC.
With 6 psi from a single Rajay turbo, we could get 450 ft/lbs all the way to about 4400 rpm - which is 375 hp in anybody's dyno room. Stock smog cam, draw through the OEM Quadrajet. Smog legal components & timing. Easily the worst cast piston made in mexico junk GM ever made. 375 horsepower. Drove like a stock engine unless you opened the secondaries.
It worked well. I still see them for sale on e-bay occasionally 30+ years later like the example below. Making a system for a 318 in an A body would mean making or modifying a passenger side exhaust manifold to mount a properly sized turbo. Really the hardest part of the fabrication comes down to that one manifold.
B.