I don't know how hard a 318 would be to get 500hp out of, I like to take the path of least resistance. A 360 with a 4" crank is easy.
My 340 was .030", 11.4-1, ported Edelbrocks, Weiand X-Cellerator, 750DP, Hughes 236/242° @ .050", .580" ish lift flat hydraulic ran 7.24 @ 94 and change at 3240# on pump 93 shifting at 6400.
If Wallace is close it was around 425HP. So what would it take to get the extra 75HP out of 21 less ci?
Using the 1/4 mile numbers Wallace says the 340 was in the 390-410HP range.
I guess a race motor with plenty of compression on alcohol with a good solid roller would be easier. All my builds are centered around pump gas though.
Again if it's so easy where are they and why aren't more people building them?
