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Compression Test Results, High??

Discussion in 'The Garage' started by mini_mull, Apr 6, 2005.

  1. mini_mull

    mini_mull 1/2 ton status

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    Ran a compression test when I replaced the plugs. (OK, my hubby did it while I supervised since I'm due next month) The numbers were all within 10% of each other, so that's good, but they seem a little high compared to other people's that I pulled up when I searched, what would cause that? Here's the results:

    8-190 7-177

    6-187 5-186

    4-180 3-183

    2-183 1-185
     
  2. Eric M.

    Eric M. 1/2 ton status

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    12 to 1 compression pistons! JK :D Good rings I guess?? I wouldn't worry about a high reading .... it's when they're low that you start to wonder :thinking:


    Eric M.
     
  3. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    sounds like you were spinning it too many times.. we usually go 5 "puffs" on the gauge..
     
  4. mini_mull

    mini_mull 1/2 ton status

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    Thanks guys, I feel better now. I guess we did spin it too many times. The directions on the test said 4 cycles or until it stopped going up. I just did the later for simplicities sake, I'll have to try the 5 puff method next time.

    My results should still be accurate as far as the variance between cylinders though, right?
     
  5. RustyMule

    RustyMule Registered Member

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    From what I know, it tops out after 4 or 5 "puffs" anyway. You could spin it all day and it won't really get much higher. And higher is never bad. :grin:
     
  6. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    Looks fine to me, just crank till the guage stops going up...
     
  7. rhuarc31

    rhuarc31 Registered Member

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    Actually those numbers are pretty right for a bone stock tbi motor in good shape. The stock cam and heads are designed to fill the cylinders up at low rpms, causing high readings. Heck the motor in my suburban hits 160's with a much bigger xtreme 4x4 grind cam. Sounds like you've got a nice healthy motor that you don't need to worry about it. BTW readings can vary as much as 10-20 lbs on identical stock motors due to stock variances in deck height and such. This doens't even call into effect atmospheric pressure that day, so i'd say you're good to go.
     
  8. Fierospeeder

    Fierospeeder Banned

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    you can have carbon coated on the piston and the heads which increases the pressure
     
  9. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    yep. carbon buildup = higher compression. :blush:
     
  10. mini_mull

    mini_mull 1/2 ton status

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    I thought if you had a lot of carbon buildup it would run rough or sputter. It doesn't run bad, pretty strong, in fact, especially for a motor w/ 214K. Should I be worried about that (carbon), or only if it starts effecting performance? Is there any way to clean it off short of tearing it apart? That's not exactly an option right now. Some kind of oil additive maybe? I don't really want to do the water thing, too nervous about home brew remedies on a DD, with no $ to fix anything that I mess up for at least a few months. Thanks for the info. Keep those explanations coming please.
     
    Last edited: Apr 8, 2005
  11. dirtwarrior17

    dirtwarrior17 Banned

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    there is really nothing you can do without tearing it apart except for valve cleaner... any kind of oil additive won't get to the top of the piston where the buildup is the worst. I wonder if one of these guys is going to come up with some sort of solvent i've never heard of that you pour through the valves once you get the cover off...

    Carbon buildup doesn't necessarily mean a weak motor... it depends on where the buildup is. If you have a lot of buildup on the valves or exhaust port then you can expect sputtering and less performance. besides raising compression the buildup on the top of the piston shouldn't hurt anything, its the other pieces that you have to worry about.
     
  12. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    you could Seafoam it....

    but i wouldn't bother, considering your looking to repower it sometime soon anyway and it runs good..
     
  13. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    10% is cool. Keep cranking 'till it stops moving. If it seems high you've either got a throttle that opens more than other peoples(you are doing this on WOT aren't you?), got a carbon build up or your motor's a bit smokey and the oil helps seal the rings up giving higher comp. :)
    Good luck with the sprog!! :D
     
  14. mini_mull

    mini_mull 1/2 ton status

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    Thanks guys. Guess I won't worry about it for awhile, if it's not going to hurt anything, at least until I can actually do something about it. That's a relief. :D
     

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