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Compression spec for B18A1

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Compression spec for B18A1

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    Compression spec for B18A1

    Hi, I searched for this, but I couldn't seem to find the exact answer. What is the factory compression specification and tolerances for a 93 LS motor? I only have the Chilton manual, and they seem to have left that vital bit of info out (even though they have references to it elsewhere in the book . I know mine is low at 150-150-150-140, but I'm just wondering how low. Thanks!

    #2
    Are you asking compression ratio? 9.4:1 or 9.8:1 I cant remember. But as long as you did the compression test correctly those #'s are "ok". General rule is as long as the number are within 10 of each other the engine is doing well.

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      #3
      I know the compression ratio (9.2:1 BTW), and I know that the variation isn't too bad. I'm just interested in how far down from the factory numbers my motor is. Does someone have a factory service manual or something that gives this spec and its tolerance?

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        #4
        the max. compression you want is about 184psi and the min. is 134 mine is at 150, 175 for the other 3. what is it doing to make you chack the compression?

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          #5
          Just curious, did you check your compression on a warm engine at WOT for 7 or more cranks?

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            #6
            My engine is a little down on power and idles a little rough, but it's to be expected. The rings have almost 340K miles on them.

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              #7
              thats alot of miles

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                #8
                Wow over 300k and still pulling 150+PSI? Hmmm maybe mine are shot then lol, my b20b has less than 1/3 that many miles and im pulling 160-160-160-165 Is there somthing wrong with my engine? Or is his of higher compression from the factory?? I thought b20b's were 9.2 or 9.6:1

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                  #9
                  Compression ratio and the compression spec aren't necessarily directly related. The compression spec for the CBR600RR is only 175psi for its 12:1 compression ratio. There are many variables.

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                    #10
                    My b18a1 had about 184k on it when I last did a compression test... it was roughly 180 across the board.

                    I thought 175 - 185 was the psi out of the factory.

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