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  1. #1
    TheXrider's Avatar
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    Need Help LOW COMPRESSION

    I just checked the compression on my 08 Motor and the compression is low on 1 and 3 is 120psi and on 2 is 115psi so I am going to be rebuilding my block and maybe the head also new valves. I am not familiar with these motors so If I have it rebuilt I want to upgrade the weakest links for example I had an 01 Ford Lightning that I was putting 525 to the wheels I couldn't put out more power because my short block would go and the weakest link was the rods the pistons and crank would hold way more power but the rods would always go. So my question is on RXP motor since I am getting it taken apart what would be the weakest link that I could upgrade? I just don't want to replace all the internals if not needed.. I would appreciate all the info given


  2. #2
    PEST!'s Avatar
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    Those compression numbers are not out of spec. if its a 185,215 or 255. Engine type is important to tell whats ok and what aint. No one makes an engine that has perfect compression between cylinders all the time so they have allowed %20 on most.

  3. #3
    GOT BOOST? Dockside's Avatar
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    I remember read a thread not to long ago a member had low compresion on all 3 and did something with the timing to bring it up.

  4. #4
    TheXrider's Avatar
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    It's a rxp-x motor witch should be the same block as an 08 215... I figured 120psi is already on the low side.. maybe the exhaust valves might not be closing all the way since they tend to corrode...

  5. #5
    Moderator Snoman's Avatar
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    Quote Originally Posted by sportsterme View Post
    I remember read a thread not to long ago a member had low compresion on all 3 and did something with the timing to bring it up.

    Correct..IF you retard your cam timing you will see the compression numbers go up..

  6. #6
    TheXrider's Avatar
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    So I might not even need to do a rebuild, I'm going to take it up to Duke and see if he can get it right...

  7. #7
    Moderator Snoman's Avatar
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    Quote Originally Posted by TheXrider View Post
    So I might not even need to do a rebuild, I'm going to take it up to Duke and see if he can get it right...

    No, From what im seeing the numbers are all within spec,,Ill bet hell retard the cam timing some and youll be fine..Youll notice better accelration once he does it too..

  8. #8
    TheXrider's Avatar
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    Quote Originally Posted by Snoman View Post
    No, From what im seeing the numbers are all within spec,,Ill bet hell retard the cam timing some and youll be fine..Youll notice better accelration once he does it too..

    Thanks.... Hopefully Duke can work on it soon

  9. #9
    Moderator RX951's Avatar
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    Make sure you have a realiable gauge too.

  10. #10
    Work Harder, Millions on Wellfare Depend On Us! ultramaxracing05's Avatar
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    maybe you can reseat the valves, by removing the retainers and go to your local car parts and buy that tapping paste and the sucking tool to reseat the valves,

    since you will be having the head off it wont hurt to do this.

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