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  1. #1
    Chrisrokc's Avatar
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    Reliability with Milled Stock Head

    I am looking to milling my stock head for either 89 or 91 octane. I have talked to Lowell and he tells me he wants me to take a hot compression reading after riding. Then when I send my head in he will beable to make the psi reading up accordingly to which ever I choose.

    Now here is my question...

    What will a milled head made for 150psi 91 octane do to the stock bottom end? I have heard many things from your motor won't last very long to it will last forever.

    Whats the real verdict?


  2. #2
    All hail the Chief! fullboogie's Avatar
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    Lots of people have run a higher compression head without a welded crank for years with no problems, as long as it's within reason. And Lowell won't give you something that isn't right. Go for it.

  3. #3
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    I am looking to milling my stock head for either 89 or 91 octane. I have talked to Lowell and he tells me he wants me to take a hot compression reading after riding. Then when I send my head in he will beable to make the psi reading up accordingly to which ever I choose.

    Now here is my question...

    What will a milled head made for 150psi 91 octane do to the stock bottom end? I have heard many things from your motor won't last very long to it will last forever.

    Whats the real verdict?

    If the bottom end is good you will be fine. If the bottom end has a lot of hours on it, it will take its toll.

    I had a MX bike that had a lot of hard hours on it but the piston tolerance was a little big so I ordered a new jug and piston. I got about 1 hour out of it before the lower end came apart in a BIG way. The compression on the worn bottom end was just a little too much for it.

  4. #4
    Chrisrokc's Avatar
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    Well I just had a slight rebuild last season because of an over heat.... damn hose...

    It including

    Rings
    Rotary shaft oil seal
    bearing needle
    o-ring
    c-clip


    Thats not a whole rebuild but they took it all apart and checked everything and put it back together good as new. Currently I have 45 hours and about 20 of those are since they fixed it.

  5. #5
    My son (mohawk man) jeffsntx's Avatar
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    Quote Originally Posted by Chrisrokc View Post
    Well I just had a slight rebuild last season because of an over heat.... damn hose...

    It including

    Rings
    Rotary shaft oil seal
    bearing needle
    o-ring
    c-clip


    Thats not a whole rebuild but they took it all apart and checked everything and put it back together good as new. Currently I have 45 hours and about 20 of those are since they fixed it.

    With 45 hours you shouldnt have any problems with it. Like fullboogie said, GO FOR IT!!

  6. #6
    Duke's Avatar
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    Quote Originally Posted by jeffsntx View Post
    With 45 hours you shouldnt have any problems with it. Like fullboogie said, GO FOR IT!!

    Ditto.

  7. #7
    Chrisrokc's Avatar
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    When will I start seeing problems though? Well possible problems.

  8. #8
    (When will I start seeing problems though?)

    Chris you are asking questions that are answered in only one way... When ever you increase the power output of any engine, you increase the load and heat on all load bearing and reciprocating assemblies, which in turn, ALWAYS shortens engine life to a certain extent. Its a hi performance piston engine fact of life. Either you want to go fast and say damn the risks and engine life, or you can sit on the porch and swing really slow and continue to fantasize in your mind what it would be like.. But remember, even totally stock engines fail also, why? Because they can! So you just never know... So be like nike, and just DO IT, you know you want to or you wouldnt be on this forum... Ross

  9. #9
    Chrisrokc's Avatar
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    Quote Originally Posted by rossnemo View Post
    (When will I start seeing problems though?)

    Chris you are asking questions that are answered in only one way... When ever you increase the power output of any engine, you increase the load and heat on all load bearing and reciprocating assemblies, which in turn, ALWAYS shortens engine life to a certain extent. Its a hi performance piston engine fact of life. Either you want to go fast and say damn the risks and engine life, or you can sit on the porch and swing really slow and continue to fantasize in your mind what it would be like.. But remember, even totally stock engines fail also, why? Because they can! So you just never know... So be like nike, and just DO IT, you know you want to or you wouldnt be on this forum... Ross

    Hahaha, your right. I wanna do it and I will.


    When I am modding LSx's (ls1, ls6, ls2, ls3, ls7, ect..) I know about what horsepower the bottom end starts to take a hit. Example, LS6 will make 550-600rwhp reliable for awhile but it will go so you better start saving for a bottom end. Is this the type of thing I will be getting my self into by throwing on a head? Or are we talking it is going to last longer than that?


    Just good to know

  10. #10
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    I ran 145 psi all last year on my GK BB . This year I stepped it up to 155-160 .. stock head milled by GK, two layers of 1200r gasket. the .010 and .008 one.
    My squish was .043 I think? I have it wrote down out side.

    It runs great !

    But with the key advance of 3* it Cranks hard. (start it be fore I leave (no chokes also) then top off the battery. I am going to a Gell battery next year.. I relocated my battery to the back. And I think the pounding took it's toll?)
    But It runs like a crazy man On CRACK! waaabaaaa!

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