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  1. #1

    GM High Perf Head Flow Numbers

    Anyone know anything about these heads as far as flow numbers?? If not, where is the best place to find them??

    GM High Performance Aluminum Heads, 2.25/1.88, 315cc runners, 119cc chambers, Rectangular ports

    Thanks, Allan.

  2. #2
    Registered Turbojack's Avatar
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    Do a search here on OSO, there has been some threads with that info. I think it was the chev magazine's website

  3. #3
    Charter Member #139 /Moderator/Platinum Member Charter Member klaw's Avatar
    My Boats:
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  4. #4
    My Boats:
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    Somethings wrong with the chevyhiperformance database. The rectangular port information is missing. The information was there a week ago but now missing. The link for category 3 BBC heads (rectangylar ports) takes you to the category 2 data (large ovals). Category 3 data is missing. I've e-mailed them but no response yet.

  • #5
    Thanks, did not have exactly what I needed, I am going to check Pace Parts......Allan.

  • #6
    Registered Turbojack's Avatar
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    Go to Air flow research's web site, they had spread sheet with a number of the different heads

  • #7
    Washed Away
    These are the numbers for gms 401 heads 118cc chambers and 322 intake port

    intake exhaust

    .100=35 .100=53
    .200=145 .200=112
    .300=200 .300=137
    .400=236 .400=170
    .500=275 .500=194
    .600=310 .600=213
    .700=330 .700=226
    .800=340 .800=234

    exhaust to intake ratio = 72%

    I downloaded this off of the High Performance site some time ago.

    They said:

    This is Chevys smallest rec port head, yet it flows extremely well for its size. Having a very similar port volume to the 990 head the 401 head flows dramatically better, especially at higher lifts. With the combination of great flow and being lightweight, this head would make a great mid-priced aluminum head for a hot street rat motor.

  • #8
    Thanks, Washed Away,
    The nymbers are very helpfull and the advise seems great too

  • #9
    Registered KAAMA's Avatar
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    A boat?....What boat??? How about a galvanized warsh tub wit a tornady strapped own da rear!
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    Western Michigan
    Washed Away,

    The flow numbers on those 401 heads from .700" and .800" lift are most likely something you are not going to see in a boat with any degree of reliability. Typically, a cam for marine use in a "turn-key" type of application is not going see .700/.800" lifts unless your out to "burn the house down" so to speak. Marine engines with decent reliability usually don't use a cam much over the .650" lift at best---this is especially true in a supercharged application. It's more the lift numbers between .200" and .600" lift that will have a lot to do with performance especially in a marine application. I too, had to learn that higher lift/flow numbers aren't going to make much difference if I am not running a cam with that kind of lift. And the more lift you use the more the reliablity is going to go away from you. I hope you understand.


  • #10
    Washed Away

    I have a pretty good idea on flow numbers. I understand that most marine applications are 3000 thru 5000-5300 rpm motors and high lift flow numbers are normally not an issue. Blower motors may be able to use the extra cfm but cubic inces and torque make the average motor go. I posted these numbers for Blown1500. I had them laying around and the quotes are from High Performance Chevy. I cringed everytime I used the site being the Mopar man that I am, but what you have to work with what ya got!

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