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C-85 Upgrade - What else while the plane is down?

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  • C-85 Upgrade - What else while the plane is down?

    I'm diving full in on the C-85 upgrade. I pulled the a65 motor today along with exhaust and engine mount. New motor should be here by the end of the month. I'd love input from others that have been through the process in general or as to what else should I consider doing while I have the plane down and access. I am planning to repaint the firewall and will clean up and paint the motor mount. Mags, carb, harness, and prop are all either new or overhauled so not much to do there. Thanks for the input in advance. The picture is of the plane as it sits today since pulling the engine. I can include more pictures/info as I go if people are interested in the progress.
    Attached Files
    Stu

    '46 BC12D
    Jefferson County (0S9)

  • #2
    Consider replacing the fuel, primer and oil lines with bulkhead fittings at the firewall in place of the grommets

    Scott
    CF-CLR Blog: http://c-fclr.blogspot.ca/

    Comment


    • #3
      If you EVER have to pull the engine again you will think Scott is a SAINT for that recommendation! Now if there was just SOME way to put a disconnect into the oil temp line!

      Comment


      • #4
        If you use the short mount, you might consider making a dish pan for the fire wall, pending which mags you use and starter and generator.

        Comment


        • #5
          Really good point on the bulkhead fittings. I can see how that would be a big help. The engine is a -12 with bendix S20 mags, however I am not planning to run a starter or generator at this point.
          Stu

          '46 BC12D
          Jefferson County (0S9)

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          • #6
            Anything you can do to make it lighter is like adding free power.

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            • #7
              Are you doing the wing mods? (or leaving those for another time?)

              Rob

              Comment


              • #8
                There really isn't much else I can get rid of to lighten it up more. I am about as bare bones as it gets for panel and interior.

                No wing mods right now. I will likely try and tackle them this winter. I would love the 80lb increase but am also trying to get it back in the air quickly given it's prime flying season.
                Stu

                '46 BC12D
                Jefferson County (0S9)

                Comment


                • #9
                  Speaking of oil temp, remember to keep the old adapter with the temp bulb.

                  Sully

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                  • #10
                    My distant recollections (from 2005) are:

                    You will probably need to "dish" or hammer the firewall to clear the magnetos. It's really tight with the -8 rear case and it's even tighter with the -12 rear case. If you can live without the -12 rear case and use the -8 you will be happier. But this may require a different part number for themag, since the gears may turn the other way on the -12. If there are any other options that are legal now (smaller mags, or somebody's electronic ignition) then that is probably well worth it. We had to hammer the firewall on mine and it still left zero clearance for getting themags in and out.

                    You will have a fair amount of small detail work and "fiddling" with the front left cooling baffle. Be prepared for this IMHO

                    Replace the rubber pushrod seals on the engine with the new leak-resistant spring upgrade thingies. Definitely worth the effort. If you don't want to do that, then make sure sure sure the stock ones fit well, and replace those awful "hog rings" with screw clamps (aka "Breese clamps"). The hog rings really suck. I would also use "fuel lube" fuel proof grease, or Permatex, or some sort of non-hardening oil-proof sealant there as well.

                    IMHO DO NOT follow the STC where it says to move the fuel valves under the instrument panel. LEAVE them in the wing root. Much safer that way... you always want to be able to sgut off a fuel leak at the source. The STC was originally based on the 1948 production re-certification, and they were trying to make the CAA/FAA happy. If you feel it is absolutely necessary to dot every i and cross every t, then call Terry and ask him to authorize this deviation.

                    While you have evrything apart, take out the main fuselage tank shutoff valve and either verify it works perfectly, service it, or replace it with a teflon ball valve. Another big PITA to deal with once the aircraft is flying again.

                    .Inspect, service, repair or replace the Dzus fasteners on the firewall and cowl s needed, most of these have not been looked at in 70 years.

                    You don't have to do the wing mods at this time, but PLEASE DO have a good look at the root fitting attach lugs. My bolt holes were worn oval, and we had to do a repair. It had been annualled over and over and over with this issue. You cam check this quickly without taking the wings off... Have someone there with you. Make sureit is absolutely 100% quiet, not even the birds chirping. Have your helper lift under one wing at the strut attach. Lift until the tire is off the ground. While he is lifting, you are listening with your ear directly against the wing root fabric at the fitting. If you hear any clunk - clunk as the airplane is lifted off the ground and set back down, this noise is coming from the root attach bolt moving back and forth in the fitting holes. Again most airplanes have not had this stuff really inspected in many years if ever.

                    I had three consecutive engine failures (power loss) on takeoff one time after I had done the upgrade. I believe this was due to the stock T-craft vent system being overloaded from the increased air and fuel flow through the larger enginee. The STC talks about a lot of additional vent lines and cross-vents between the wing tanks. All that is just fine, but remember the wing tanks do not feed the engine on this system, they only re-fill the main tank. So I am guessing (GUESSING) that there is no positive vent on the stock main fuel tank other than the hole in the cap where the float gauge wire goes through. I cannot remember whether the STC adds vent lines to the main tank or not, but I vote for adding some kind of a forward facing vent line to the main tank. Whether that line goes up and ties into the wing tanks, or the new crossfeed, I can't remember. However or wherever it is done, I vote for adding more venting capacity to the main tank. The "fix" for the power loss on takeoff, supposedly from the Luscombe world, was to pull carb heat on takeoff, which reduces the fuel flow requirement to the engine. So you get to give up part of the extra power you just installed.

                    What was mentioned regarding bulkhead fittings in the firewall... I WISH I had been smart enough to do that ! Definitely a first class idea !

                    Lots of other small airframe mods and upgrades could be done during this time, but that falls even further outside the scope of the OP.



                    Taylorcraft : Making Better Aviators for 75 Years... and Counting

                    Bill Berle
                    TF#693

                    http://www.ezflaphandle.com
                    http://www.grantstar.net
                    N26451 (1940 BL(C)-65) 1988-90
                    N47DN (Auster Autocrat) 1992-93
                    N96121 (1946 BC-12D-85) 1998-99
                    N29544 (1940 BL(C)-85) 2005-08

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                    • #11
                      The 85 STC's tank venting can be improved via larger diameter forward pointing upper tank cap vents, and if a third non-pointing vented cap replaces the original wire gauge. Atlee Dodge sells both of the vented cap styles.

                      Edit: The STC calls for the main tank to be vented through the wing tank(s) with forward pointing wing tank vents fabricated. Fuel lines are sized according to expected demands for flow and the three gallon main tank minimum recommended for the F-19's and later advisable for earlier 85's and Strokers. In my experience exposed tank vents can become temporarily plugged by snow and insects so a backup vented cap on the main tank (with the vent protected from the elements) might be worthwhile. That's how mine's rigged.

                      http://www.fadodge.com/fuel-cap-for-180hp-piper/
                      http://www.fadodge.com/fuel-cap-vented/

                      Gary
                      Last edited by PA1195; 07-02-2019, 13:46.
                      N36007 1941 BF12-65 STC'd as BC12D-4-85

                      Comment


                      • #12
                        I would install a new header tank valve, fuel lines and hoses. P leads, are also another common complaint. The Bendix mags are a pain because of the shielding and adapters needed to fit to the mag.

                        I would also look at how you are going to mount the gascolator, I have moved it to the firewall to clear the Luscombe exhaust, I also put stainless hard line between the header tank valve and gascolator and I built a braided teflon hose between the gascolator and carb with a fire sleeve.

                        Replace that oil pressure line with one that is braided teflon and fire sleeve it, also get an orfice fitting for the engine, I recommend the ones from Vans aircraft, it has a .040" hole in it.

                        What kidney tank are you going to run? I would get a new oil tank cap gasket, most rebuilders and sellers dont change them.

                        New 5/8" aluminum vent line and do the aerobatic breather mod. Also put on new Mil-6000 hose for the breather fitting to the line. If you can send me your old fitting, I can solder in a brass tube for a small fee.

                        I would also make sure that every hole in your firewall is sealed, if you have a small hole, stick a screw in it with a washer. Now is the time to fix your baffling.
                        N29787
                        '41 BC12-65

                        Comment


                        • #13
                          Originally posted by PA1195 View Post
                          The 85 STC's tank venting can be improved via larger diameter forward pointing upper tank cap vents, and if a third non-pointing vented cap replaces the original wire gauge. Atlee Dodge sells both of the vented cap styles.

                          Edit: The STC calls for the main tank to be vented through the wing tank(s) with forward pointing wing tank vents fabricated. Fuel lines are sized according to expected demands for flow and the three gallon main tank minimum recommended for the F-19's and later advisable for earlier 85's and Strokers. In my experience exposed tank vents can become temporarily plugged by snow and insects so a backup vented cap on the main tank (with the vent protected from the elements) might be worthwhile. That's how mine's rigged.

                          http://www.fadodge.com/fuel-cap-for-180hp-piper/
                          http://www.fadodge.com/fuel-cap-vented/

                          Gary
                          5/16" ID valve header tank valve, which I have, -6 line in both solid and hoses to the engine.
                          N29787
                          '41 BC12-65

                          Comment


                          • #14
                            This is sorta' going beyond normal needs but I've installed these caps on large fuel tank vents exposed to the elements on a few planes. Cut the end of the tip off the cap so the tank can breathe while parked through a small hole and later remove before flight for full air vent flow. It'll keep out snow, rain, and most insects.

                            Gary

                            Click image for larger version

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

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                            • #15
                              Well since the engine is off, weld in a 3/4" tube and tabs so you can put in toe brakes, it goes forward of the pedals.
                              N29787
                              '41 BC12-65

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