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What should i get off a compression check from a 10:1 355?

Discussion in 'The Garage' started by dirtwarrior17, May 6, 2005.

  1. dirtwarrior17

    dirtwarrior17 Banned

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    Just need to know what kind of psi i should be looking for out of a compression check on a 10:1 355.

    thanks,

    shane
     
  2. Jagged

    Jagged 1 ton status

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    10:1 is a pressure ratio right... so it'd be ambient pressure times 10 i would suppose ;)
     
  3. 1979jimmy350

    1979jimmy350 1/2 ton status

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    take the reading that you get and divide it by the atomspheric pressure. For example if it is 14.7 psi when you do the test you should get around 147 psi on the test. This is only a rough estiment other factors like valve timing can effect the readings. This should get you close though
     
  4. chulisohombre

    chulisohombre 1/2 ton status

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    if i remember right from when my engine building friend told me.if you have at least 120 or more per cylander you are still alright and dont need a rebuild yet.
     
  5. Jagged

    Jagged 1 ton status

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    it depends a lot on current weather and altitude too (less air to compress at higher altutudes and in low pressure weather systems)
     
  6. dirtwarrior17

    dirtwarrior17 Banned

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    Does anybody have a psi off a 10:1 motor... Im looking for a psi "ballpark"
     
  7. 1979jimmy350

    1979jimmy350 1/2 ton status

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    i said the ballpark would be around 147 psi at sea level.
     
  8. dirtwarrior17

    dirtwarrior17 Banned

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    OH.... does it get higher or lower with more elevation?

    I've heard people getting 160 psi on stock comp so i guess they spun it too many times or somethin.
     
  9. Jagged

    Jagged 1 ton status

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    Higher elevation = less ambient air pressure = less air compressed... so in short, lower at higher elevation.
     
  10. 1977k5

    1977k5 3/4 ton status Vendor

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    The psi itself doesn't mean anything, as long you are within a few psi you are fine. Mine has 9.7:1 and at 6000 ft. read 160 psi all around.
     
  11. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    Compression will vary due to cam duration but 160~180 is a good ballpark number. More important is how close the spread is, if this is your new motor it should be damm close or identical across all the cylinders.
    George
     
  12. unclematty

    unclematty 1/2 ton status

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    Thank you for correcting these guys, ambient pressure is directly related to your altitude and the weather( to put it crudely) 14.7 is the standard reading at sea level and at 59 degrees F' If you live at a higher elevation the pressure will be lower. any way to answer the question is for a 10:1 compression engine is approximatly 175 - 185 psi, assuming there are no problems. I only say this because I have tested a few hi-comp engines, not because I worked it out mathmatically :D
     
  13. dirtwarrior17

    dirtwarrior17 Banned

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    cool.... thanks guys...

    As soon as i get my hands on a gauge (couple days) i plan to see if i got screwed off ebay. I REALLY doubt i did but i want to make sure...

    And yes this is my new motor.
     
  14. beater_k20

    beater_k20 Banned

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    camshaft has a lot to do with it. not only the profile of the cam, but the cam timing as well (assuming you degreed it, probably not). no way to accurately say this is good, and this is bad. honestly, a compression test is pretty pointless anyways. you've got a brand new engine, why worry about it? if you want to know something about your engine, do a leakdown test.
     
  15. dirtwarrior17

    dirtwarrior17 Banned

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    I've had it opened up 3 times and am about to finish up cleaning out the heads and start it up.... i want to know if anything got into the cylinders and damaged any after i run it for a few seconds.

    I NEED to get the prominator and labtop but now i'm getting nothing from my dad(owes me over 2k) so I'm mobbin the honda for a couple months.
     

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