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Cathedral vs Square port heads

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  • Cathedral vs Square port heads

    Talking to a couple racer friends from down south and I made a comment about cathedral port heads being better than the new big square port.
    They respectfully disagreed and said to check with anyone who knows cyl head flow #s and sent me a bunch of links proving me wrong.
    So I found the article below. To summarize--this article clearly shows the LS3 square port flow numbers being far superior to cathedral, but dyno power gains weren't that different.
    My question is if flow numbers don't matter--then why pay to have cyl heads flowed anyway? Just for cfm bragging rights?
    I can't put square port heads on my 346 anyway, so it doesn't matter to me. I'm happy with my 243s with lightweight valves.
    The question of the day seems to involve the difference between the original cathedral-port and modern rectangular-port LS heads. More specifically, which one i

  • #2
    Some of these cyl head dummies don't know squat about what happens when you run a head that has a port that too big. Sure the big port will flow more air "it's bigger" duh, but the quality of the port is more important than just air flow numbers. Here's what those dummies don't think about, would you take a 355 SBC and dump a 265 cc head on the engine and go out and race or street it? NO because the 355 would be a big mutt performance wise. Same thing goes for a 364 LS engine, a new sq. port head at 265cc is too damn bid for that engine. Same goes for the BBC with the sq. port head on those engines they are always too big on the smaller engines. I proved in the last couple of years that you can run tiny heads and make great power to blow the doors off a lot of bigger headed engines for sure. My belief for a 6.2 is, if I were to put a set of 235 cathedral cnc ported heads on my 6.2 I will kick you ass at the track and on the street against a 6.2 with the sq. port heads. If I were to build a 5.7 LS engine I would use a set of ported 4.8 heads, better compression and a stronger head when I get done porting them. 6.2's are pigs at the track, had an old codger tell me that his 2011 Camaro SS was faster than my peanut port BBC engine in my Camaro. He got ass raped at the track, not only did he get beat badly he still could not figure out how I beat him so bad with outdated parts LOL.

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    • #3
      Yup - when the ports (or valves) get too big for the engine, scavenging is worse due to the velocity being too low.
      There is more stupidity than hydrogen in the universe, and it has a longer shelf life. - Frank Zappa

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