The cost to build a 350P is a bit higher than the 400 simply because of volume. There are 20 400s being built for every 350, so pistons and rings are less expensive. The rest of the parts are not only similar, they are the SAME. For dollars spent versus power gained, no comparison between 350 and 400. The 350 cranks DOES "fit" in the 400, but balancing IS required.
If you have "small valve" heads, and really want to stick with the smaller engine, it can be made to run VERY well. many will use "large valve" heads because Pontiac did on some engines. This is not the best way too make power with the small bore. The small valve heads will flow better under these conditions, especially if proper porting procedures are followed.
To make "real" power with it, you're going to need to "rev" it high, as with any smaller cubed engine. This calls for high qual;ity rods and pistons, in particular, and good valves and springs, as well. A solid lifter cam will go a long way to producing really good power numbers.
Rick C.,
For clarity only, I must point out a couple of misconceptions you appear to display. First, catalytic conveters, mandating "unleaded fuel" first appeared in 1975, under EPA laws. Unleaded fuel doesn't "clog" the converter, where lead does. Initial EPA rules for EGR (exhaust gas recirculation) were for '72, but many manufacturers weren't "ready" so they pushed it back to '73. Pontiac WAS "ready", and the '72 intake is unique because of it. It's a sort of a "cross' between the '71 (non-EGR, early crossover) and the '73 (EGR, "later" crossover). The '72 has the later crossover, but not the EGR provisioin. Good intake... Anyway, the induction-hardened exhaust seats were first found in SOME of the '72 heads. ALL for '73. It was felt the added heat from leaning the idle could harm the exhaust seats (correct assumption). While to a degree, it WAS about "unleaded fuel", mostly it's for longevity in a higher heat environment than originally designed for. Adding the converter compounded the problem.
Lastly, a 350 Pontiac isn't REALLY 350 CID. It's 354, but GM didn't want any one division "stepping on the toes" of other GM divisions, so they ALL were called "350". Each division except Caddy, had their own "350", unique from the others, until around '77, when "corporate" engines became the rule.
FWIW
Jim
