454?

[Taylorman]

Is the gen IV the most common bbc. im starting to look for parts to build a bbc and need to know which one is best to build. im assuming its the gen IV. Also, is rectangle or oval port heads better?

[napabob]

This might help:
http://www.macmaster.on.ca/bbgm.htm

[hondajoey]

the 454 is the way to go for motors, if you are gathering parts for a 454 the rectangular port are the best heads for max HP but if you find a older set of the oval port heads that have the big openings they work good, some of the later 70's 454 oval port heads have small intake runners.
i would stick to the gen 4 stuff, unless you can get a hole gen 5 set up block,heads, oil pan, intake, that the older stuff wont match up without special head gaskets(i was told this I dont know for sure)
the bellhousing & mounting is the same

[TIMINATOR]

Ported oval ports w/ big valves to 5500 rpm, after that, square ports. Dual plane intake to 5500 rpm, then single plane. Unless you like a looker that doesn't run, and/or uses a lot of gas, stay away from tunnelrams and dual carbs. Most jetters around here suffer from "MONO HOLLEY-NON-CHROME-APHOBIA" thats the fear of having only 1 carb and not enough chrome. Me, I have 1 Holley, no chrome and black headers. But it runs good and doesn't use much gas (regular). Your choice may vary. BUT you may want to catch a ride in mine first..... TIMINATOR