New Peanut Port Big Block

Discussion in 'High Performance Modifications' started by 1980RS, Mar 9, 2019.

  1. 1980RS

    1980RS Veteran Member

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    I looked up some exhaust flow on the 236 heads and 781 heads. The 236 head has the same port as the 781, but the 781 flows about 25% better. I though that was pretty interesting.
     
  2. jeff swisher

    jeff swisher Veteran Member

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    I have been accused of that.
    I had a guy race me years ago and said he was shifting his stock 76cc head 355" at 8000 rpm with the 270H comp magnum cam.
    I ran the same cam and was shifting at 6900rpm with ported and milled double humps in a 350"
    I went for a ride with him and said it feels weak and you are early shifting it.
    I looked at the tachometer and sure enough 8000 rpm.
    He had it on 6 cylinder.
    After switching it to 8 he still shifted early because 2 years of driving it that had become habit.

    I later ported his heads and picked up a lot more rpm and power but he still could not beat me.
    He then got 64cc sportsman II heads 200cc runners and ran the same. sounded different though.

    It is not that I need to switch my tachometer it is I need to get out of the 1970's way of building things.
    The time when 5.40 gears were good street gears and BBC's early shifted at 7000 rpm.
     
  3. 1980RS

    1980RS Veteran Member

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    I got a call from on of my friends today, who tried to tell me that once you port peanut port heads they flow the same as an AFR 265 head, ya no, I told him and he says he has the data to back that up, ok. I for one know the limits of those little heads and if that was the case everyone would get the little port heads. This is the same guy that last fall asked if I want to trade my PP heads for his Procomp heads, I passed on that. I don't need the headaches that those heads have. Good news, the 360 ported heads are getting flowed next week, keep you posted on results.
     
  4. jeff swisher

    jeff swisher Veteran Member

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    You should have asked for his proof.
    But even if he made them flow the same I feel there could be a big chamber difference.
    Now I did see one spot in the chamber that was talked about on a forum on the exhaust side.
    It is on the flat deck area directly behind the exhaust valve behind the long side .
    The flat deck area was opened up and tapered like a slide it was said to really increase the exhaust flow.

    Now look at the peanut port chamber and now look at a 781 and do you see a difference in that area.
    [​IMG]

    Look at the LS head notice that slide shape going off the flat deck into the exhaust valve.

    On a pair of my 601 heads I have on my 57 chevy now I tapered the entire edge right there intake and exhaust both.
    Just as an experiment and at 10.87 compression they have not dis
    disappointed me.
     

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