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compression?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by baldbandit, Feb 14, 2001.

  1. baldbandit

    baldbandit 1/2 ton status

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    how much compression should a small block chevy run? I'm fixin to run a compression check on my 400. It is weak and probably needs a rebuild but i would like to run a compression check first. A tune up might help, but i feel like a compression test would tell me what i need to do.

    baldbandit
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I would guess that if it was around 120 to 150 and all cylinders within 10% of each other that would indicate a decent set of numbers. My old Ford F250 with 130,000 miles on a 400M (dog) was 150 across all but 2 cylinders, the other two were 160 and 155. It ran pretty good and wasn't a high compression engine.

    Rene

    [​IMG]
     
  3. baldbandit

    baldbandit 1/2 ton status

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    Thanks! I'll be doing the compression check saturday. weather permitting!

    baldbandit
     
  4. Butch

    Butch 1/2 ton status

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    It is going to depend on what size heads you have and what kind of pistons. If it has dish tops and 76cc heads you will have in the 120 to 125 range. Anything less than 100 and you will lose most of your power and foul plugs alot. If you are 115 or better and like Rene said within 10% then drive it a while. If you do get a cylinder that is low take a squit can and give it two or three squirts of motor oil into the cylinder and recheck the compression if it goes up 10psi or more then your rings are shot. You probably know, but the motor should be at normal operating temp as well

    I thought I was wrong once,
    but I was mistaken<P ID="edit"><FONT SIZE=-1>Edited by Butch on 02/15/01 07:55 PM (server time).</FONT></P>
     

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