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Tune up and secondarie woes.....-gctid401966

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    Tune up and secondarie woes.....-gctid401966

    Hey guys, this may sound amatuerish, but hear goes......

    I put my 89 2556 5.7/omc in the water for a little fishing trip. After getting up on plane and pulling back to about 3600rpm we are cruising nicely when we start loosing rpm. And i mean alot of rpm, continues to drop till its only at 2200. I let out of it thinking maybe a clogged fuel filter and it would catch back up. No such luck. Temperature isnt high, plenty of fuel. I shut it down and we decided to fish where we stopped. Upon restarting, i notice a miss. After pulling wires at cap, i see its missing on number 5 and 7. Changed those plugs and we start back. Still a definate miss. Barely get 2200rpm out of it.

    I bought this boat with very little hours on it (under 100) and before i put it back in service i did the usual for a boat that sits up that long. IE cap,rotor,plugs,points,condenser,wires,carb rebuild,timing,fuel system cleaning,oil change. Distributor advances correctly and base timing is correct.

    After getting it home i did a compression test and i notice 0psi on 5 and 7. So off comes the valve cover to see if maybe it bent some push rods. Both intake valves were too tight. I adjust them and my compression returns to 160psi! I put it back together and double check timing and now its purring like a sbc should.

    Here are my questions; 1. How did they get so far off, and why at 97 hours? Ive built many 5.7 sbc's and normaly after getting up to temp once or twice you adjust the valves and your good to go for a while. It seems odd that they tightened up the way they did. The po who owned this boat was a good freind and he only cruised the chesapeake bay for a short while before he and his admiral were caught in a storm. She wouldnt go out anymore and he dry stored it. He never abused it, had all the maint done at the dealership(he was a bayliner salesman). I cant get my head around it...

    2.My secondaries never opened on the way back. I figured this could have been because the valve problem, but they still wont open. Are they adjustable on marine carbs? I remember adjusting the spring tension on these on my hot rod. Hopefully its a little too tight and the engine vacuum cant overcome it. It is a qjet btw.

    I will be taking it out monday i hope, and plan on doing a fuel pressure test and playing with the secondaries then. I'll post as i go and learn more.....:hypnotysed:

    #2
    Well , i decided to hook up the muffs and try a little diagnosing in the driveway. (Bad weather) I pulled all the plugs and did another compression test. #1-160,#2-160,#3-162,#4-138,#5-101,#6-160,#7-160,#8-161. I shot oil in the #4 and #5 and it didn't come up at all. Also i noticed there is alot of moisture coming through the vent tubes back to the spark arrester. Could this be a blown head gasket? Ive seen them blow straight to the water passage before but there is no water in the oil. The way this is designed ,i can't tell if there is steam going out the exhaust.....anyone have any ideas? I'm so grateful for all the expert advise so far. I've been doing auto and equipment repairs for awhile but this is pretty new stuff. The 5.7 isn't that complicated, i'm just not familiar with these cooling systems and exhaust. Thanks for taking the time to read this and please feel free to give me anything you have!

    You pros out there don't know how much you guys help us and are appreciated sometimes!!!!!!:worth

    Comment


      #3
      Re; your post #1:

      How did you determine that the #5 and #7 intake valve rocker arms were too tight? I understand that re-adjusting re-gained valve operation and brought your cylinder pressure back up.

      But had these actually been set incorrectly, it would not have taken very long to damage these two valve seats.

      Rocker arms do not typically become too tight..... they typically loosen.

      FYI, some will go through valve adjustment (of which is actually cam follower plunger depth adjustment) on a fresh engine using the 2 or 3 stop static procedure.

      IMO, this is a NO NO! :thumb

      Instead, use the 8 stop static procedure, and go right down the firing order beginning with #1 TDC C/S, and while doing both Int/Exh simultaneously........ and/or use the dynamic procedure once up and running.

      NOTE: there is approx .100" plunger travel within a SBC cam follower (aka "lifter"), so you'd need to be off quite a bit in order to cause any damage.

      Let's assume that these did become too tight after the initial adjustment!

      IMO, the only plausible cause would/could be a valve that has been settling into the valve seat. This would bring the valve stem up taller.

      As the valve stem becomes taller, the rocker arm now sets the plunger deeper into the cam follower.

      If the plungers were to reach the bottom of their travel, the cam and cam follower would now prevent full valve seating, of which I could then understand.

      But why no valve seat damage as displayed by your NOW good cylinder pressures?

      If these had been adjusted incorrectly from the get-go (perhaps favoring the bottom of plunger travel), a slight settling into the seat would/may explain this.

      Re; your post #2:

      I now see in your second post that these two cylinders did not fully recover.

      This takes me back my explantion of the cam follower plungers preventing these two valves from fully seating during the compression and combustion cycle.

      If so, and if the 2 or 3 stop procedure had been used, spread the word.

      This is NOT the procedure to be using, IMO! rod

      I've some lengthy conversations with the good people at MichiganMotors, and they do NOT use this procedure, for what that's worth to you guys!

      .
      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Comment


        #4
        Thanks for the confirmation Rick.

        I came up with the same thing. I can only think of the valve droping in the seat to cause this . I did the adjustment the first time by setting tdc #1, adjust it ,turn crank 90 degrees and follow firing order, adjusting as i go. The second time i did it running with a modified cover. (cut out top portion to allow access to rockers). I just can't understand why they dropped, maybe the old gas that remained in tank forming deposits and burning seats? Just a guess. Anyway i guess i'm pulling heads now.

        What about the moisture in the arrester? Maybe a bad head gasket as well? If it is maybe ill get lucky and won't have a burnt valve......

        Do i need any special gaskets for marine application or is it the same as an auto? I have a head set in my shop if its nothing special....

        Is there anything else you would check or look for before pulling it apart?

        Is there a way to drain block so water doesn't get in engine when i pull manifold and heads?

        Would you recomend an aluminum intake? I have a fairly new weiland split plenum...

        I know i have alot of questions but my dad taught me a long time ago, "There are no dumb questions when your asking with the intent of learning".

        Thanks again for the insight!

        Comment


          #5
          711brett wrote:
          Thanks for the confirmation Rick.

          I came up with the same thing. I can only think of the valve droping in the seat to cause this . I did the adjustment the first time by setting tdc #1, adjust it ,turn crank 90 degrees and follow firing order, adjusting as i go. The second time i did it running with a modified cover. (cut out top portion to allow access to rockers). I just can't understand why they dropped, maybe the old gas that remained in tank forming deposits and burning seats? Just a guess. Anyway i guess i'm pulling heads now.

          What about the moisture in the arrester? Maybe a bad head gasket as well? If it is maybe ill get lucky and won't have a burnt valve......
          • 1 wrote:
          • Do i need any special gaskets for marine application or is it the same as an auto? I have a head set in my shop if its nothing special....
          • Is there anything else you would check or look for before pulling it apart?
          • Is there a way to drain block so water doesn't get in engine when i pull manifold and heads?
          • Would you recomend an aluminum intake? I have a fairly new weiland split plenum...



          You are welcome.... don't know if it helped you much.
          • 1 wrote:
          • #3 suggests RWC'd engine. If so, then yes, you will need the Marine head gasket set.

            If CCS, then a high grade automotive set will work just fine.
          • I think that this points to valves, but if curious, do a cylinder leak-down test.
          • Yep, remove the side engine block drain plugs, and probe them for rust scale debris.
          • Not if RWC'd. The PH of river/lake/ocean water will eventually cause problems... and likewise with head early automitive head gaskets.

            If CCS, then yes, that would be OK.



          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            Thanks for the help buddy, i'm off to gather the gasket set and hoses to start this job. I'm so glad i installed the camper top for the boat, now i can work in the rain!

            Attached files [img]/media/kunena/attachments/vb/705818=29926-561385_481932151821709_2053750958_n.jpg[/img]

            Comment

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