Compression

Discussion in 'Softail Models' started by thehoggyboy, Dec 27, 2010.

  1. thehoggyboy

    thehoggyboy Member

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    Hi Guys, Just a quick fire question, I have a 2006 Heritage Classic vance & hines big radius exhaust, Spike air cleaner, No engine Mods, 33000 K's (21000 Miles) Compression 3 times front cylinder 145,145,145, 3 times rear cylinder, 145,145,145, Engine warm not hot, possibly could have gotten a little higher but the battery faded on me. I dont have any probs that i can hear,feel, or smell,Just wondering if these figures would equate to a healthy engine, Thanks for your help Guys. Regards Steve.
     
  2. R.Bingham

    R.Bingham Active Member

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    Both front and rear cylinders are reading equal which is good. I would only be concerned if they were more than 3% different.

    What elevation are you at? If you are at a high elevation that would contribute to the low numbers.

    Did you hold the throttle wide open during the test?
    If not that can contribute to the low numbers.

    What brand of compression gauge did you use?
    A cheap gauge can give an incorrect reading.

    According to the Big Boyz calculator, an 06 TC 88 with stock cams(06 H-D injected 40* intake close) @ sea level you should be around 156.5 psi.
    At 1000' above sea level it drops to 152 psi. If you are at a higher elevation it will cause you numbers to be lower.

    When you get ready to update the cam chain tensioners you might want to look at the Andrews 48N conversion cam. It will really wake that 06 up. It has a 29* intake close and a lift of .548". This will be considered a bolt in cam for the 06 because it has bee hive springs which will accommodate up to .575" of lift. This will bump up your CCP to 164.7 psi @ sea level. And it will bump up your performance all across the board.:s

    Randall
     
  3. thehoggyboy

    thehoggyboy Member

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    Randall, thanks for the reply mate I am that close to sea level it doesn't matter, Brisbane Australia.The tester i was using was a Grimek screw in type, and yes i am thinking about wakening the beast and your info is greatly appreciated,and will be kept in reference, And yes i did the test wide open throttle,but the battery turned up its toes pretty quick which made me think i could have gotten a little higher and as per your numbers at the moment i think i am running very well.Once again mate thank you.Steve.