Announcement

Collapse
No announcement yet.

C90 rocker arms

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • C90 rocker arms

    I learned something in the last couple of weeks.

    Probably old news to many of you.

    C90's have an intake rocker arm and an exhaust rocker arm that are different.

    Apparently the intake one is not drilled with an oil hole to the valve.

    Seems to me that I have never seen such a rocker though.

    Do the get commonly replaced by the drilled version?

    Dave R

  • #2
    Re: C90 rocker arms

    3-23. ROCKER ARMS AND SHAFT
    Two rocker arm assemblies are pivoted on a tubular
    steel shaft, which is ground on its outer surface to a
    push fit in the cylinder head support bores. The rocker
    is a steel forging with a bronze bushing. A pushrod
    socket is machined in the lower end. The valve
    contact surface, at the upper end, is hardened and
    ground to an arc. A small oil hole, drilled from the
    center of the pushrod socket, intersects a hole drilled
    upward and through the bushing wall. A groove
    around the bushing's inner surface carries the oil
    channel to a second vertical hole, which ends in a
    squirt nozzle facing the valve stem. An orifice in the
    valve stem end of the exhaust valve rocker arm
    provides lubrication to the exhaust valve stem during
    engine operation.

    P/N 639614 Intake; 639615 Exhaust
    N36007 1941 BF12-65 STC'd as BC12D-4-85

    Comment


    • #3
      Re: C90 rocker arms

      Thanks Gary,

      I have never seen them, each engine I have seen has drilled rockers on each valve.

      Makes me curious.

      Dave R

      Comment


      • #4
        Re: C90 rocker arms

        As an owner and non-A&P I asked the same question Dave. On one C-90 overhaul of mine we sent them out to be yellow tagged and what came back were all drilled 630615. I guess the interesting question would be what's the problem with that? Maybe oil on the intake would contribute to oil consumption? These parts are around $500 new from Continental. Reconditioned likely less. Maybe Dr. Tim knows or other rebuilders here?

        Gary
        N36007 1941 BF12-65 STC'd as BC12D-4-85

        Comment


        • #5
          Re: C90 rocker arms

          I suspect the bigger problem is NOT having them all drilled because then there is a good possibility that an exhaust valve gets a non drilled by accident.

          Where as if they are all drilled all valves get cooled and lubed.

          Dave R

          Comment


          • #6
            Re: C90 rocker arms

            Yes. Good point Dave. Unless there's a disadvantage to having a drilled oil rocker on the intake, then why not offer that option? Maybe those that deal with this overhaul process can comment.

            In the meantime......http://www.tcmlink.com/pdf2/M77-19.pdf which offers some fog clearing info and this link implies AES can drill the arms to meet 630615 oiler specs http://www.aircraft-specialties.com/...s-rocker-arms/ which may be why they returned all of mine drilled?

            Gary
            N36007 1941 BF12-65 STC'd as BC12D-4-85

            Comment


            • #7
              Re: C90 rocker arms

              Yep, I remember an O-200 that the mechanic got distracted while reassembling and swapped the drilled and non drilled rockers. It made it about 35 hours before it ate the exhaust valve over Stevens Pass in WA. Lesson learned! I'll take them both drilled anyday!
              John
              I'm so far behind, I think I'm ahead

              Comment


              • #8
                Re: C90 rocker arms

                Originally posted by N96337 View Post
                Yep, I remember an O-200 that the mechanic got distracted while reassembling and swapped the drilled and non drilled rockers. It made it about 35 hours before it ate the exhaust valve over Stevens Pass in WA. Lesson learned! I'll take them both drilled anyday!
                John
                On the pilotsofamerica website, there is a mechanic in Washington state that put an 0-200 together, put in a C150 and the engine quite 35 or 40 hours later, the FAA found the bolts in the camgear broke and fell out with the saftey wire in two of the bolts, and the cylinders had "a black substance" around the skirt and cylinder base O-ring on 3 of the cylinders, the 4th cylinder didn't have anything on the cylinder skirt, the case halves had the same "black substance" on the mating surfaces, later the mechanic said the bolt were "owner supplied", but he is still an IA, so I guess the FAA gave him a pass, sure doesn't sound like the engine was assembled according to the MM

                Comment

                Working...
                X