how can i get 400hp out of a 318?

Rat Patrol said
You're off beam on the issue of strokers -

Nobody with any intelligence would say that a stroker is going to make more peak HP than a std stroke block using identical compression, heads, induction and camshaft.....what works for the std stroke will starve the stroker - not that anyone would build either motor the same way anyhow.

The point of choosing the stroker route is simply to arrive at a more versatile and less temperamental SB engine for a target HP.

The OP didn't specify what type of "duty" the engine was going to see -Or did I miss that?

I'm guessing most engine builders would know from running a three speed trans auto on the street - anything you can do to lower converter stall, compression, increase torque at a given RPM and smooth out cam lope is a win on a hot stinking day in Arizona in work day traffic.

However - If its a race car - go nuts.....I recommend 13:1 comp and Avgas with Eddie heads and 1 &7/8 TTIs.

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I put an ebay ($1,000.00) Vortech supercharger on a 360 Magnum that had been treated to a set of TTI headers, an air-gap Chinese clone intake manifold and a Hughes cam. Those are the ONLY performance pieces on the otherwise BONE STOCK engine. It makes 10 pounds of boost.

The blower took it from a 13.35/102mph to mid 11s @ about 117. Made a different car out of it...

There was no "KIT" so I did all the necessary mounting stuff, myself. It was frustrating, but fun, too.

Here is the dyno sheet from a local \chassis dyno, and a coupe of pictures...
If you believe the 85-percent for the chassis dyno figure formula, it makes 525 flywheel hp.

Anyone with a 318 could do the same, with only minimally smaller output, I think. JUst an alternative to a big cam and high compression...