Compression test results and plug color question.

Small Block Mopar Engine

  1. MileHighDart

    MileHighDart Well-Known Member

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    So the other day I decided to run a compression test on my 5.9 magnum. Haven't done one since I put the engine together a couple years ago, so just decided to check it out.

    Numbers look pretty even across the board, all between 139 and 144.

    Plugs look kinda of black and sooty probably because the choke was on most of the time when I was warming it up before the test. (im guessing). But I know it's probably running a bit rich too.
    So most of the plugs are black or brown, but wondering whats up with #8 ?
    Looks bright white compared to the others. Any Idea why that one looks so lean?

    IMG_20191111_121158425.jpg
     
  2. yellow rose

    yellow rose Doctor of Thinkology.

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    What plug is that? You definitely have some distribution issues but number 8 looks the best at cruise. The rest of it would be a guess with the shells on the plugs but if it's that pig rich at idle and cruise it's probably pretty rich at WOT.

    What carb and intake? Cam timing?
     
  3. jimjimjimmy

    jimjimjimmy lobsterman FABO Gold Member

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    [QUOTE="yellow rose, post: 1972736343, member: 4180

    What carb and intake? Cam timing?[/QUOTE]
     
  4. MileHighDart

    MileHighDart Well-Known Member

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    Edelbrock Magnum airgap. Edelbrock 1406 carb. It's got a 5.2 Magnum cam. Don't remember all the specs right off, but I know it's 112 lsa and 110 installed center line.
     
  5. MileHighDart

    MileHighDart Well-Known Member

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    P S. I am getting ready to finally install my Innovate air/fuel gauge so I can dial in the carb a little better.
     
  6. yellow rose

    yellow rose Doctor of Thinkology.

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    Don't use the gauge until you learn to read plugs first. The gauge can send you down a rabbit hole.
     
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    • GEO

      GEO Sarcasm Inc.

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      number eight does looks odd, kinda like a head gasket issue where it is sucking coolant in the combustion chamber
       
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      • oldkimmer

        oldkimmer FABO Gold Member FABO Gold Member

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        Or a vacuum leak on number 8. Kim
         
      • 70aarcuda

        70aarcuda Master Hoader of SBM FABO Gold Member

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        at 5307 feet above sea level...i would be changing some metering rods...or jets around.
         
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        • RustyRatRod

          RustyRatRod Weenie idiot loser. FABO Gold Member

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          What's that plug read from? Did you just take um out after driving around or did you do a wide open blast like you're supposed to and cut it immediately off? Exactly WHAT are we reading here? If it's idling in the driveway, They look pretty dang good.
           
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          • MileHighDart

            MileHighDart Well-Known Member

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            Yes, it was just idling in the garage till warmed up. Didn't know about doing a wide open blast before pulling the plugs. And I didn't really pull them to read the plugs, but to do the compression test. Just thought I'd ask what you guys though cause #8 looked so much more white than the rest.
             
          • RustyRatRod

            RustyRatRod Weenie idiot loser. FABO Gold Member

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            Yeah. You caint read plugs like that. You're supposed to get it up to temp, do a full throttle blast through the gears and "I" always shut r down before I even come to a stop good so the engine doesn't get into idle at ALL. Then look at um. Opinions vary, but that's MY method.
             
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            • greymouser7

              greymouser7 Vagrant Vagabond “Veni Vidi Vici” FABO Gold Member

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              thankyou
               
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              • famous bob

                famous bob mopar misfit FABO Gold Member

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                There was a pretty well known racer around Tulsa quite a few yrs. back , had a new 426 stage 3 wedge, 63 plymouth. He was going to do a plug read/chop the throttle , throwing it in neutral/shutting it down at the same time , to acuratly read the plugs. He went thru neutral into reverse , he ended up with jaws wired closed , and sold the drivetrain to another friend, that's all that was left !. He quit dragracing .
                 
              • midnight340

                midnight340 Well-Known Member

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                Having a reverse lock-out (like on the B&M Pro Stick) takes some getting used to, but I like it to avoid the risk of this sort of thing.

                ALSO if you have a locking column be careful shutting down, you need to be able to go where you planned!!
                 
              • RustyRatRod

                RustyRatRod Weenie idiot loser. FABO Gold Member

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                Those car were NOT play toys, even in "stock" form. If you can call it stock.
                 
              • RustyRatRod

                RustyRatRod Weenie idiot loser. FABO Gold Member

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                Exactly why they are NHRA mandated. I've always like them too, but they are a trick to get around quick sometimes.
                 
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                • midnight340

                  midnight340 Well-Known Member

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                  My local Mopar machine shop (that has built and raced Mopar engines for many years) has mentioned to me that it's not too unusual to have some fuel distribution variance, in particular, to be leaner on #8. Something about it being an end cylinder in combination with the way the firing order is designed.

                  And maybe this would be worse at idle as well???
                  (this according to my memory of a conversation months ago, so... you know.) :)
                   
                • yellow rose

                  yellow rose Doctor of Thinkology.

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                  There are 4 cylinders with an extra corner in them, even with a single plane intake.

                  I'm thinking (not ready to test yet) that some of those distribution issues are really reversion related. I can't prove that, but that's what I think.
                   
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                  • TrailBeast

                    TrailBeast Slightly Twisted Member

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                    Do you have a PCV, and where is it connected?
                    Might be the answer this time, but Rob is spot on about plug reading.
                     
                  • MOPAROFFICIAL

                    MOPAROFFICIAL Well-Known Member

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                    Be careful if you have power brakes before shutting it down.

                    Check port alignment to head.
                    Disconnect the pcv, plug it and drive it cruising, no wot and then check the plugs again...who knows.

                    Everyone else have covered most things to check. Shortest wire of a set of crappy high resistance plug wires perhaps, lol. Maybe not, maybe you have good wires...maybe you fouled the plugs at one time, short of that one and they never cleaned up. Lol
                     
                    Last edited: Nov 24, 2019
                  • famous bob

                    famous bob mopar misfit FABO Gold Member

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                    Not many reverse lock outs around in 1963--------
                     
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                    • famous bob

                      famous bob mopar misfit FABO Gold Member

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                      Agree with this post, we flowed 3 diff. intakes and there was a bunch of diff. in them , read hughs intake tests.
                      I got the victor down to 15 cfm scatter, and a toquer 2 down to 25, a weiand team g down to 24 , and I aint no pro -----
                      Would love to have Wilson manifolds do one for me , but $1500 is a too much for me !
                       
                    • midnight340

                      midnight340 Well-Known Member

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                      True dat!! Unless you count the Hurst Mystery Shifter that I couldn’t get into reverse!!!!! :rofl:
                       
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