273ci thoughts?

MoparLeo said

The part that has the biggest effect on HP is the cylinder head and because of the small bore, big valve heads will not work. The intakes would contact the block unless you grind relief notches in the deck. Keep the 273 what it is. Any 4 bbl 318, 360, 5.9, or 5.7 will far out perform the 273 and have unlimited parts available.

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True but we don't know how much actual effect the bore size will have on flow. Haven't seen anyone do flow numbers a 318 bore nevermind 273. Did see one article on 350 vs 305 bore sizes on some Chevy cylinder heads and there was like a 10 cfm difference. I know 305 has a bigger bore than 273.

To get 400hp out of 318/340/360 the formula seems to be 200-220 cfm heads 10:1 cr and a 285 ish cam. With a 273 probably got to add another 20 cfm. The main problem for some would be at 400 hp you would need to turn the 273 around 7000 rpm.
If I was gonna build a 273 between 250-400hp I'd go with mild ported stock valve size magnum heads on a notched block with some 4.??:1 gears out back.