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  1. #1
    Napkins........ I Fly a Starship seajm's Avatar
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    Questions pertaining to GP1200

    Hey guy's,
    I wouldn't say I'm new here, but I've been lurking here for about 2 years reading this and that. Thanks for all the great info and tips, but I've come across a snag and can't seem to find what I'm looking for. I have 2 Gp1200's one stock the other some minor mods, but let me cut to the chase the GP that runs I'm a little concerned about. I have about 110 psi comp. all the way across. I can't seem to find any info on acceptable readings on the 1200 non pv plenty on the 1100. I'm using a new Actron comp. gage, is 110 acceptable? or is it time for a top end? I have about 162 hrs now. I have a Pro Design head with 30cc domes I want to install, but I don't want this motor to let go on me because of this. Any input would be much appreciated!!! Again, thanks for all the info and tips, very helpful!


  2. #2
    Mpeavler's Avatar
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    As long as the 3 are within about 10psi from each other your good. Stock is around that so as long as they are close your good. Keep in mind unless you use a good compression gauge, they can vary from 10-15 psi per gauge. IMO...if all 3 indicate that...your fine!

    M

  3. #3
    Flying Scotsman's Avatar
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    Quote Originally Posted by seajm View Post
    Hey guy's,
    I wouldn't say I'm new here, but I've been lurking here for about 2 years reading this and that. Thanks for all the great info and tips, but I've come across a snag and can't seem to find what I'm looking for. I have 2 Gp1200's one stock the other some minor mods, but let me cut to the chase the GP that runs I'm a little concerned about. I have about 110 psi comp. all the way across. I can't seem to find any info on acceptable readings on the 1200 non pv plenty on the 1100. I'm using a new Actron comp. gage, is 110 acceptable? or is it time for a top end? I have about 162 hrs now. I have a Pro Design head with 30cc domes I want to install, but I don't want this motor to let go on me because of this. Any input would be much appreciated!!! Again, thanks for all the info and tips, very helpful!
    30 cc domes on a pro design head would be 215 psi if im not mistaken better be running race gas lol.........

    I think there more likely 38 cc or 36 cc

  4. #4
    Napkins........ I Fly a Starship seajm's Avatar
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    Quote Originally Posted by Mpeavler View Post
    As long as the 3 are within about 10psi from each other your good. Stock is around that so as long as they are close your good. Keep in mind unless you use a good compression gauge, they can vary from 10-15 psi per gauge. IMO...if all 3 indicate that...your fine!

    M
    So 110 is acceptable for a 1200? I thought that a 110 was good for a 1100. What is a good gage in your opinion?

  5. #5
    Napkins........ I Fly a Starship seajm's Avatar
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    Quote Originally Posted by Flying Scotsman View Post
    30 cc domes on a pro design head would be 215 psi if im not mistaken better be running race gas lol.........

    I think there more likely 38 cc or 36 cc
    I hope they are 36cc or 38cc! I am being told that they are 30cc domes. I will cc the domes when the head gets to me. I just don't want to blow this motor by putting this head on. In just about 2min. I'm dropping 8 bills on a 140 hour fresh water 1200 for my stocker GP. I don't feel like dropping even more for another motor. Those biatches are not easy to come by. SBT is a little shakey for my taste!!

  6. #6
    Old Ski Insanity w/rpm500's Avatar
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    personally I use a Snap-on gauge set, though my older K-D tool gauge has been acceptably accurate.....


    take note: this high of compression put extra stress on other parts of your motor and may lessen the life of the motor before rebuild or replacement...

  7. #7
    Napkins........ I Fly a Starship seajm's Avatar
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    Quote Originally Posted by w/rpm500 View Post
    personally I use a Snap-on gauge set, though my older K-D tool gauge has been acceptably accurate.....


    take note: this high of compression put extra stress on other parts of your motor and may lessen the life of the motor before rebuild or replacement...
    Oh man, you can guarantee that if those domes are 30cc they WILL NOT be installed. I'm only looking for about 150 psi give or take. I might put those 30cc domes on my B1!!

  8. #8
    Flying Scotsman's Avatar
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    I have some 38 cc domes for a pro tech head and they look like there stamped 30 cc if you dont look closely.
    I think that may be the case.
    Send me the 30 cc domes and ill try them in my head when I get my ported cylinder done someday.

  9. #9
    Napkins........ I Fly a Starship seajm's Avatar
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    Quote Originally Posted by Flying Scotsman View Post
    I have some 38 cc domes for a pro tech head and they look like there stamped 30 cc if you dont look closely.
    I think that may be the case.
    Send me the 30 cc domes and ill try them in my head when I get my ported cylinder done someday.
    Ahhh, I don't ever read that chit. I'll cc them with a syringe. So what your saying is that you want to trade domes if they are 30cc?

  10. #10
    Moderator OsideBill's Avatar
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    The pro design domes are stamped in the side.
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