Everyone knows it is vitally important to keep your expenses as low as possible, but I would like to encourage you to "hang the expense" when it comes to engine installations. To let things slide or try to get by cheap in this area only provides a false sense of economic security, and can actually cost you in many other ways. Following are a few suggested priorities to follow when installing a fresh engine on you ag plane:
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Find a knowledgeable mechanic, who knows the particular engine being installed, even if you have to take the plane to him or pay his travel expenses to come to you. It will be worth it! (Note: "A & P" is not always equivalent to "Good Radial Engine Mechanic")
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Use all new hardware, especially where fiber lock nuts are utilized. Has your R-1340 ever whistled to you while idling on the ramp? Chances are, this was caused by worn out fiber locks being used to install the carburetor. Everyone hopes to get at least 1600 hours out of a new engine, which is reason enough to install fresh mount rubbers with each zero hour engine. And remember: no two engines will run or feel exactly alike.
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I feel strongly that fresh engines should have fresh accessories, especially the primary engine accessories such as carburetors and fuel pumps. Spend some time checking around to find which manufacturer's accessories are holding up the best, as well as the cost of the product.
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There are several publications available to you as reference material. The Pratt & Whitney Maintenance Manual (PN 118611) is one of the best available. Another good source is Air Tractor's 8-page article entitled, "Radial Engine Tune-Up." The P & W manual is available from Covington Aircraft and I'm sure Air Tractor would send you a copy of the article if you requested it. This material will save you time and money, while also providing more accurate information than you "buddy up the road" could ever hope to give you!
Properly cleaning the oil system, along with replacing the oil cooler, will eliminate many headaches with a freshly overhauled engine. This is especially important on engines installed on aircraft that have experienced a previous engine failure, and therefore, have generated a lot of metal contamination. I have found that it is virtually impossible to get all of the metal out of an oil cooler unless it is disassembled and "boiled out," and the oil lines to and from the engine are pressure washed or flushed out. It is also important to remove the stand pipe/screen from the tank for flushing.
Thoroughly clean the prop and the governor. The oil dome on the Hydromatic and the Piston/Cylinder on the Ham Standard are both effective centrifuges and will collect large amounts of sludge and contamination (or flake metal). Flush out the governor with a lightweight oil or diesel and check for hand operation. I should turn with only light to medium hand pressure and feel smooth.
You now have a fresh engine with a really clean oil system! All new "lord" mounts and installation hardware are in place, everything is hooked up properly, and all control linkages are checked for full travel (hopefully with some "cushion" allowed). Service the engine with the appropriate weight non-detergent mineral oil.
Your engine should now be ready for priming the oil system and then cranking her up. I want to stress the importance of properly priming the oil system on the radials, especially on engines that have been in storage for sometime. I recommend the following procedure:
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Remove the top two rocker covers, main engine sump drain plug and the front spark plugs
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Crank the engine with the starter until you see fresh oil at the valves on top.
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Flow approximately one gallon of oil out of the engine sump.
Note this procedure will probably require considerable cranking, so allow your starter sufficient cooling time between cranking periods, (no less that three-minute cranking periods are recommended).
Finally, I would like to address engine operation during the break-in period, or first 100 hours of operation. Most OHC radial engines are equipped with channel chrome cylinders that do not require any special type of delicate handling during break-in, like the steel cylinder engines do. In fact, babying a chrome engine has actually proven to be detrimental to the piston ring-to cylinder seating process. Chrome cylinders tend to "glaze" when operated at low manifold pressure and abnormally cool operating temperatures.
While marginal glazing does not directly effect performance, it does effect the piston ring's ability to scavenge oil, resulting in greatly increased oil consumption. In my opinion, a freshly overhauled engine should be operated with the same power settings that you normally work with on an engine that is already broken in.
God bless you this season!
