The "Throw Away 318"

Dave_J said
318 or 340 pistons and rings being the main differences in costs, what is the reciprocating weight savings? A set of 318 pistons and rings will weigh less... and then if you balance the crank and remove weight out for the 318 piston set, its even lighter.

If you max port the heads and use the same cams, at a MAX build of both engines, what is the HP ratings? Maybe the maxed 340 will make 20 to 25 more horses but the 318 will rap a little quicker.

A free 318 short block VS a $1000+ 340 block is the main argument here for some.
That $1000+ will go a long way on that FREE 318 block.

Someone that is PRO 340 will always find some argument to support their feelings. ;) But if you give me a 340 block I'd make a 426 stroker out of it.

If max power is the point, a 340 would be the answer, whether stock stroke or stroked. Using the same crank and rods in either block is just a few cubes difference.
The larger bore 340 will have less valve shrouding which will help breathing. Knowing that, cam selection can compensate some along with judiscious porting.
Again I would say if you have a 340 or 360 then use it. If you have a 318, build it with the research and correct parts combination to build a strong runner and be happy.
The biggest cause of the 318's bad rep is the cam the factory installed. The Chubby 305 has a similar rep for the exact same reason.A friend had a 1980 Pontiac 2dr with the sloped back window that had the 305 4V. Pretty regular oil changes and the car lasted longer than him. 440,000km or about 243,000 miles. The plastic cam gear finally packed it in so he had an RV style cam installed with a double roller timing set. The heads were never off and it ran well. His brother has it now. So the basic engine is not the problem. Pull the stock cam and use it for lawn darts.