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Thread: Broken rocker arm jet valve tab

  1. #1

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    1986 Dodge Ram 50
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    G63B

    Broken rocker arm jet valve tab

    Hey...

    Not that it makes any difference now, but...I didn't pass California smog...too high NOx....tech suggested it was EGR...so while I was toying around the motor I pulled off the valve cover and discovered that the no. 2 rocker arm broke off its jet valve tab... the tab and the adjusting nut and screw were carefully lodged in the recess where the fuel pump rod runs through to the fuel pump, I don't believe this is what caused me to fail smog as every plug was snow white so I retarded the hell out of the timing and got the color to come back on the plugs...so I probably screwed up the timing install at some point...anyway, what could have possibly made the tab break off the rocker?

  2. #2

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    Adelaide, South Australia
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    1985 Mitsubishi L200
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    G63B
    Jet valves usually burn out from running too lean but it is possible it seized for some unknown reason. Is this the first time you've pulled the rocker cover off to inspect it? Maybe someone in its previous life over adjusted it when trying to set the clearances... How much did it fail emissions by? That one dead jet valve = 25% less exhaust gas recirculation into the engine (when looking at how much ex gas enters the intake system it isn't a lot to start off with, but there wouldn't be an allowance between a pass and fail)

  3. #3



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    Pittsburgh, PA
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    1980 Dodge D-50
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    G54B
    Jet valves are fresh air injection for swirl at under 1/2 throttle - no connection to EGR, but it does lean out the charge sort of, if the stock carb is in use.
    Pennyman1
    The best Dodge that Dodge never made
    Living the D-50 lifestyle since 1980

  4. #4

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    Thanks for the input guys....Geez...no, I have had it off before, the last time was about 4 months ago when I pulled the motor to replace the clutch and all the motor seals. In California there are about 4 different categories of emissions tested at 15 mph and 25 mph...the motor was incredibly clean at every category and both speeds except NOx....excessive combustion chamber temperatures. No smoke, no smells i.e. oil fuel etc.... just a bunch of invisible atmospheric hazards...so says our state government. Anyway, I'll just keep working on it, I really like these little trucks...bought my first one in 1979 as a service truck for my plumbing business, and was so impressed with it I bought 2 more...I no longer own a plumbing company (still take side jobs) but it is fun to tinker with it and attempt to bring it back to what it was back in it's day...IMHO the best import truck of it's time....btw guys...O'Reillys does not have a listing for the jet valves...Rock Auto also does not list them...are they a dealer only item?...same for the rocker arms, I didn't look at RA yet but I will in a bit.

  5. #5



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    1979 Dodge D-50
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    Chevy V6
    Install a delete kit for the MCA valves. Cut off the arm ends. Clean out the EGR and hook up so it works again. Replace the cat if she fails again. The timing can not be out more then 1 or 2 deg or they will fail you. In the old days we could crank it way retard to pass. Not any more. Check all timing marks cam, crank and running. The High NOx tells me the cat is on it's way out. CO = carb HC = engine internals NOx = EGR or Cat. It's a after burn problem. You can dbl check with Claych and noahwins
    Oh and check the air injection system to the exhaust manifold
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