Done this a couple of times; no bore nothing required, but IMO a waste of time.
The 318 is compression challenged to say the least, and big port heads just make it sluggish out of the gate. And the 340 cam just makes it more sluggish.
IMO, if you wanna wake a 318 up, just throw a 2800TC at it, a small-port 4bbl, dual exhaust and the biggest darn gears you dare drive. She does real good with 4.30s, pretty good with 3.91s, good with 3.55s but no less than that, until you bring the compression up..
With the factory cam, those big-port heads are a waste, and usually a pressure loss, and that kills bottom end. The late closing intake of the 340 cam bleeds more pressure, so the bottom-end goes away some more. If you keep the 2.76s found in most teener cars, you will keep her in the sluggish zone until ~40 mph. Sux to be there.
If you actually wanna spend money on the teener, the absolute best thing you can do for her is pump up the compression, then dual exhaust, then a 4bbl., and no cam until you bump the compression.
If you do the above including gears, then I recommend a lil more valve spring, so she'll go to at least 5000rpm,5500 is better, still on the factory cam. This really helps the car jump at the gear change.
4.30s will let her hit 60@~5000 in second gear with 26.5tires.... and that will be killer, I know, and still as virgin, but with duals and the 2800 to launch with. You won't believe it's the same engine. Hyup I ran that engine that way for about three winters, in my hotrod, while I freshened the 367.
