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Looks RICH to me

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    #16
    I agree with the possibility of rings. When an engine runs rich for a while, they wash the oil film off the cylinder walls and the rings round edges and polish the bores. One that happens, it's a runaway feedback loop and just progressively gets worse. This also lowers the octane of the fuel by adding oil vapor to the mixture, causing MORE un-burned fuel, causing MORE cylinder wall damage etc etc etc.


    Can you post some close ups of the cylinder walls?

    We have a DBilas ITB m20 car here at the shop right now. The previous shop had botched all kinds of things and caused cylinder wash down. We pulled the oil pan and pistons in situ, deglazed the cylinder walls, found 4 cylinders with rings not only stuck in the lands, but three top rings and one second ring was actually broken. New rings, plop it back together and this time will get a proper tuning session. I've had several of these type jobs over the years - and the very reason I keep repeating that the m20 does not need to go with larger injectors, specially a stock one.
    john@m20guru.com
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    Transaction feedback: Here, here and here. Thanks :D

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      #17
      These are the best I have. The car is back together and running great.

      Re-ringing in the car that is badass!



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      JH
      HIK Fab

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        #18
        Well, apparently the rings are fine! :)

        And yes, we have re-ringed several motor in situ. When you get down to the bare block, you wonder why you just didn't pull it, but it does cut down the overall working time. This particular car only had once snag that backed us up a few hours, the previous shop welded the headers and exhaust as one unit. Derp.
        john@m20guru.com
        Links:
        Transaction feedback: Here, here and here. Thanks :D

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          #19
          Awesome

          FFirebird your engine work is amazing and Thanks for all you do around here!
          HIK Fab

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            #20
            Originally posted by JGee View Post
            Awesome

            FFirebird your engine work is amazing and Thanks for all you do around here!
            And thank you guys for keeping these heaps around, so my shop has work. :p

            With the new forum layout, it took a minute to find this post and update. The bad injector car had the rings swapped out and the couple cyls that were ~60psi jumped to 180-185, and the rest were in that range. Started the car up, and it obviously had a bad mass. used a laser IR thermo and had odd readings (approx). Cyl 1,2,3,4,5,6: 280,320,360,130,310, 380, 370. Seeing #1 & #2 rings were broken on #1 & #4 and three other compression rings were broken, I gather the lean cyls detonated and snapped the rings. Compression in the cyls with good second rings all did 180psi before, bad cyls were 60psi and 120psi. The high numbers on the cyls with broken rings probably was due to the excessive blow by and oil coagulation in the rings after shutting down.

            when the pistons were pulled, there was a ton of carbon buildup, took many rounds of ultrasonic cleaning, measuring, and checking to make sure they were usable. The car now has 180-185psi across the board, BUT, #4 was still at 125-ish hot on the primary. Pulled the rail, slid a [iece of cardboard under them, and hit the starter switch - #1 shot a 2"pattern, #4 shot a 1/2" pattern, the rest were easy 3+". Swapped in a couple used injectors, now the temp patterns were in pars for the three throttle sets (ITBs). Client is sending the injectors to WitchHunter for flow matching and rebuild, the car will come back to do a throttle balancing, then we will go to the dyno and live tune it. This is now a rebuilt bone stock m20 with DBilas ITB's, and will have an actual live une for the system. Will be interesting to see how they compare to the several other engines we built with(out) ITB's etc, and add to the dyno library:





            john@m20guru.com
            Links:
            Transaction feedback: Here, here and here. Thanks :D

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