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Thread: Has anybody ever had their GS1100GL (or other 8V) head ported?

  1. #11
    Join Date
    Jun 2008
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    New Buffalo, Michigan 49117
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    5,717

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    I found this guys videos recently. His slant head 6 engine build is very informative!
    Reducing weight by grinding off overbuilt parts and casting flanges, inside and out. Very good concept goals in describing his work on a very crude engine head.
    "Only fe' collected the old way, has any value." from His Majesty O'Keefe (1954 film)
    1982 GS1100G- road bike, body, seat and suspension modded
    1990 GSX750F-(1127cc '92 GSXR engine) track bike, much re-engineered
    1987 Honda CBR600F Hurricane; hooligan bike, restored

  2. #12
    Join Date
    Dec 2019
    Location
    Columbus Ohio
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    187

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    I have been in automotive performance for about twenty years now, and I do understand the principles of cylinder head porting. However, I limit my porting work to reworking manifolds and leave the head work to the guy I have been trusting for almost twenty years. There are many many more ways to screw up a head than there are to help it, and what looks good to me doesn't necessarily look good to gas molecules moving at 2/3 mach.

    The head is now in the hands of my machinist. I have instructed him to do only light port cleanup since I don't want to spend a heap of money to make only a small improvement in power that requires me to u[grade carbs anyway.

  3. #13
    Join Date
    Apr 2005
    Location
    APE Willow Springs, Ca.
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    645

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    Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.
    Speed Merchant
    http://www.gszone.biz

  4. #14
    Join Date
    Jul 2009
    Location
    New Zealand
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    3,477

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    Quote Originally Posted by Big Jay View Post
    Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.
    I was recently shown a CNC port mill locally. Imported from the US. We looked through the heads that were already pre-programmed into it and one caught my eye.
    It was for the late pro-stock Chrysler hemi heads. Valve angles look very close to the GS 8V heads.
    I asked if it had a scaling function on the machine- and the answer was yes.
    If I ever do another 8V race GS engine I may well go this route - if the customer can afford it.

  5. #15
    Join Date
    Aug 2012
    Location
    Columbus, Ohio
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    3,601

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    Quote Originally Posted by Big Jay View Post
    Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.
    Hmmm...this sounds tempting! I'm looking for everything I can have done or do myself to make a GS400/425 big bore engine really scream, yet still not such extensive porting or large cam that it's a race-only high-rpm-only engine... I assume the old 8V engines would have the same type of small seat throat issue, and could benefit from some seat throat boring and porting in this same fashion?
    Last edited by Chuck78; 05-13-2020 at 11:52 PM.

    '77 GS750
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