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Thoughts on engine selections......

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  • Thoughts on engine selections......

    I have been browsing places like barnstormers for a while to get an idea what good (or possibly good) cores are running.

    I seem to be seeing that 0-or IO-360 cores seem to be out of sight-----8-10K for an "as-is" prop strike high time motor----
    more for a mid time prop strike. I see some of the lesser-in-demand motors are less than half that for the same general condition.

    I am guessing that all the RV builders who need motors have driven up the prices of the 320's and 360's.
    I WAS thinking that a IO-360 with high compression pistons making 200 hp might be a good selection for the 4 place.
    less weight than the 540 but part of the way there in HP. But it looks like the chances of finding a reasonably priced core may be
    small. (this sounds like a partial clone of Lycoming's experimental version)

    I have also heard of some converting lycoming -360 's to 390's by using over bore pistons + cylinders. It appears that gets to
    about 200HP with standard compression.

    If I dont use an O-360 or IO-360 Lyc. core---- there seems to be little middle ground- in terms of weight- between that and the lyc. 540.
    There is the cont. 360 which could put out 210 hp---- but is weighs all most as much as the Lyc. 540. Plus it has the more difficult
    engine mount design. (or at least -- less common--) (If I build the mount myself anyway-- is that any problem ?) I read somewhere that
    the Cont. 360 cores were way less than the Lyc. 360's --- but when I have been looking -- they appear to be just as expensive........ (?)

    I wonder if it could be possible to find a prop strike 360---- and get it before the insurance company can buy it from the owner as part of the settlement ? I am guessing that maybe the insurance companies wouldnt pay the claim if the owner sell any parts beforehand. ????
    I would guess that the insurance company is effectively purchasing the hull from the owner- and they might decline if it was not intact ?
    Of coarse you might luck out and be there when an un-insured plane groundloops---- but that would be improbable I suspect....

    I expect lots of you have traveled down this road before...... if you all have any ideas. I could also just collect individual parts
    as well---but I wouldnt expect that would be any price advantage over a complete core. and with a complete core-- you know everything
    is compatible. (there are so many variations of the 360 )


  • #2
    From my point of view, the -540 is the best bang for your buck. This would be my sales pitch:

    The weight savings aren't really adding utility, because it's CG that limits most of your operations. I never run out of useful load in my machine, no matter how much weight I put on the nose. The -360 or -390 is probably the best for short landings mind you.

    Yes a 360 with high compression sounds attractive because you get a theoretical 200hp. With such a small engine generating so much energy, overheating is going to limit how long you can run 180 or 200 horsepower. Whereas a 540 will run at 210hp all day long without exceeding 400*F. A highly stressed 360 is going to have a much shorter lifespan than a lightly stressed 540. There's no free lunch.

    There's also no substitute for horsepower. A small block 540 delivers between 250 and 290hp, which is a big jump from 195hp. In a backcountry environment, this alone is probably the one deciding factor to rule all the others. If you are cruising over flat lands, the option for extra airspeed is also nice.

    The added cost of running and maintaining a 540 is negligible, leaning means the cost per hour can be almost identical. When you consider the 540 core will probably be cheaper to acquire and last you much longer, the real cost per hour is equivalent or possibly even lower on the 540. If a light stressed engine goes 3500hrs that makes a huge difference to the economics, compared to an overstressed engine which might be lucky to make 1500hrs.


    • jaredyates
      jaredyates commented
      Editing a comment
      Excelent points for sure. Also keep in mind that the high compression pistons are going to require higher octane fuel. With the uncertain future of TEL and thus 100ll, one might not be wise to put such futute ooerational restrictions in place for such a modest HP gain. You can always prioritize output or reliability, but you don't get both without huge R&D. I always cringe when folks say "it's good enough for a race car so it's good enough for an airplane." I'd hate to end up with an airplane that required the maintenance schedule of a race car.

  • #3
    ^^^^What J Battson said.

    Most airplanes designed for a 4 banger are seriously compromised by putting a 540 in it. The Bh, kept moderately light, is not. With a 4 cylinder you will run out of CG before you run out of useful load, unless you are putting 500 + pounds in the front seats. You CAN make it equivalent by mounting the 4 cylinder a few inches farther forward.

    Bob's price for a 540 is a smokin deal. I haven't heard any complaints about his engine productsw.

    I still think the "ultimate BH" has a big 4 cylinder mounted a few inches farther forward. But that gives me a less powerful engine, at greater cost. Slightly shorter landing distance, Longer takeoff distance. And at this point, I would be a test pilot for a 400+ cubic engine, very expensive engine.

    For me, now, I will put a 540 in it.


    • #4
      Thanks guys......
      Strangely---- all of those points yall make seem right down the line common engine sense from my modest knowledge base.
      I dont think it too hard to take some of the highly stresses air race engines-- and look at their time between failures---- and extrapolate
      backwards the other way and see the reliability advantages of THAT ! Say you are actualy using 100 HP at a medium cruise
      (picked a random number) ---- it seems obvious that spreading that between 6 cylinders instead of 4 will greatly lower the stresses
      on the engine. And - all else being equal- should lead to greater life span and less chances of cracks somewhere. (and reduced thermal stresses)

      There seem to be LOTS of models of 540 out there---- does there seem to be a favorite version for the BH to use ? That is---
      which models should I be watching for ? Are there versions that can use either fixed or CS props ?



      • #5
        I had alot of the same questions when I was choosing an engine, though I knew that I wanted a 360 for the lower initial cost and fuel burn (and weight). Battson makes a good case for the 540 also. I'm very happy with the 360 but having flown the 540 I can tell you it is nice if you don't mind its few drawbacks.

        My suggestion is to find an engine builder that you trust, explain your mission to him, and give him your money. In my case this person was/is Bob. There are so many variants out there, and so many things you don't know about a core when you buy it. If Bob buys a core that turns out to have a bad crank, he spreads the cost of it over several engines. If you buy one with a bad crank, the cost of your engine just went up by several thousand dollars.

        I realized after two weeks of engine research that there was no way I'd be able to acquire the level of knowledge or the supply chain of someone like Bob with even a year of research, so why not pay him for those skills? In the end the cost of his ready-to-run engine was at most a couple thousand dollars more than I'd have been able to buy the parts and outside services for, and that's if I got lucky and did everything right. Engine building is a specialty. You can do it yourself, but it's a safe bet you'll spend more in the end, especially if you put any value on the cost of your research hours.
        Last edited by jaredyates; 05-16-2018, 08:03 AM.


        • #6
          What about the Continentals? A 470 core can be obtained significantly cheaper than a 540. I know, Continentals are heavier than the Lycomings, I've struggled to find good data on exactly what the weight differences are because it's not clear whether the listed weights include accessories or not. I think Whee touched on this in another thread.

          My project came with an IO-470 core, and I've struggled a bit deciding weather or not to use it.


          • #7
            One thing I would consider with either engine is to have the heads ported and polished. I got my cylinders from Lycon and they will port and polish them for around $300 per cylinder. They claim a HP gain of 3-5 HP per cylinder, so 12-20 HP for a 4 cylinder or 18-30 HP for a 6 cylinder. All its doing is improving airflow into the engine, there isn't any extra stress on the engine as far as I can tell so I don't see it hurting longevity or reliability or anything like that. A pretty cheap way to get some extra power, especially if you are on the fence about high compression. I personally went with port and polish and high compression. My Patrol performs great on the IO-360, I think the 4 place would be fine on 200 HP, but would be a lot more impressive / fun with 250-280 HP.
            Rollie VanDorn
            Zanesville, OH
            Patrol Quick Build


            • #8
              I've been told that the 6-cyl boxer-style engine is the most naturally balanced engine design of all normal engine cylinder configurations. I have flown both 6 cyl and 4 cyl aircraft, but not enough to make good comparisons. I do know that on the Subaru boxer engines, I much prefer the 6. I have owned 8 Subaru cars and wife and I currently drive a 6 and 4. The 6 is so much smoother and has power to spare. We took a 1400 mile trip last week and we opted to take my older high-mileage 2011 6-cyl because it is so much nicer to drive. I averaged 28+ mpg for the trip; my older 4 cyl Subes never did that well at freeway speeds. I am installing an O320 in my Patrol. Wish I'd had access to a 150 hp 6-cy aircraft-engine when I was out shopping.
              Last edited by bergy; 05-18-2018, 08:07 AM.


              • #9
                Now you have got me thinking if I am doing the right thing.....

                I have an Aerosport IO540 in my RV-10 and I love it. I had it port and flowed and it runs beautifully. With the Bearhawk B, my thought was to build light and put in a 4-cylinder. I have no need for super-STOL performance and thought I could save money and increase payload. But if what you guys are saying about the C of G is right, I'm wondering. I did, however, believe that the longer engine mount for the 4 cylinder compensated for that.

                Anyway, I am looking at Aerosport's IO375. They put on a longer throw crank to give the extra capacity, so it messes a bit with the compression ratios. The standard pistons give you about 7.9:1 (which means that MOGAS can be used) and 195hp. The high compression pistons come in at about 9.5:1 and 205hp - but 100LL only. I do not intend to routinely use MOGAS but, being in Africa, it is nice to have the option if needed. So I am going for the 195hp version. With port and flow and PMags, I think I will probably get around 200hp anyway......

                Now, in the summer around my area, I routinely get density altitudes in the order of 5000'. Am I going to be short of power?


                • jaredyates
                  jaredyates commented
                  Editing a comment
                  I wish you could come fly with me so that you could get a sense of what a 360 Bearhawk can do... it is a very capable and sprightly airplane. And I've not yet encountered a real-world load that I couldn't carry, regarding CG, Max Gross, or otherwise. During testing I loaded to the limits with concrete bags, and it was noticeably more sluggish, but even when we travel in luxury to Oshkosh and weigh everything that goes into the airplane, we run out of space and still have 200 pounds to spare. Everything is a tradeoff. You will have less power with a 360 than a 540, but unless you are routinely climbing above 8000 feet with a full load, you'll still have a really useful airplane.

                • PaulSA
                  PaulSA commented
                  Editing a comment
                  That's good to hear. To be fair, I operate out of a 550m (about 1800') grass strip. It has a 3 deg slope so we TO downhill which also often has a 5-10 knot tailwind. The RV-10 has a gross weight of 2700lb and I haven't yet tried a max weight TO in summer but I have done around 2500lb with no "puckering" moments..... As I said, 5000' DA in the summer so I only get about 26.5" MAP and 2550 static RPM.

                  So I guess with the higher lift wing, lower speeds and less gross weight, the IO375 will work with the B

              • #10
                Actually the altitude thing is why I ultimately went with the 540. At 8k it is still putting out 180 hp.
                It was a bit of a tossup for me. I could have been happy I am sure with the 360.


                • #11
                  This is all good stuff - and i am soaking up every drop ! -- more please........ :-)


                  • #12
                    The only consideration I would add about the IO-540 is to avoid the "dual-mag" versions. The dual mags are getting more and more difficult to find new, and many mag rebuild shops are no longer working on them. But I don't think Bob would suggest one of those to you, anyway...
                    Jim Parker
                    Farmersville, TX (NE of Dallas)
                    Patrol Quick-Build Serial # P312


                    • #13
                      Originally posted by JimParker256 View Post
                      The only consideration I would add about the IO-540 is to avoid the "dual-mag" versions. The dual mags are getting more and more difficult to find new, and many mag rebuild shops are no longer working on them. But I don't think Bob would suggest one of those to you, anyway...
                      I agree with that, my Maule had the dual-mag and it always worried me, I knew another Maule owner who crash landed in the Alaska wilderness when his failed. Having said that, if you found a cheap O-540 with the dual-mag, you could install a single mag and an electronic ignition. There are IO-360 angle valve engines that have them also, Mooney used them.
                      Last edited by rodsmith; 05-19-2018, 09:44 AM.


                      • #14
                        As long as we’re on the subject, I have an O-360-C4F in my Maule, so it’s a reasonable likeness to a 4-place with a 180 in it. My 360 shakes like a madman, especially when it’s cold. Exhaust cracks and subsequent repairs are frequent in this setup. In the Bearhawk community we have more exhaust options, especially more robust ones from Clint and the like.

                        But it does beg the question, is there a counter-weighted O-360 that won’t vibrate the plane apart?
                        ​Christopher Owens, EAA #808438
                        Project "Expedition"
                        Bearhawk 4-Place Scratch Built, Plans #991
                        Bearhawk Patrol Scratch Built, Plans #P313
                        Germantown, Wisconsin, USA


                        • #15
                          Did my last BFR in an M7 with a fixed pitch 180 hp Lycoming O360... was very smooth. Two days ago tore into an O320A2B 160 horse with less than 200 hours on the overhaul. Vibration was horrible. The prop was sent in for service...didn’t pass inspection. Installed a new Cato....vibration decreased a bit but still vibrates so damn much we decided to tear it down to check the weight of the opposing cylinders. Turns out the Rods were less than 1.7 grams. The pistons were within 0.8 grams. Dial indicated the crankshaft prop flange...less than 0.0015” of runout. Turns out the flywheel had a couple bolts and nuts from a previously undocumented static balance on a past prop.... found a cracked exhaust flange, and one additional crack and a missing tail pipe clamp at the muffler. The big find was the gookumpucky the A&P/AI used between the cylinder base flange and crank case....and quite a few under torqued cylinder base nuts. Will check the valves, guides and seats. Depending on condition may grind the seats and valves....and cross hatch the cylinders. New gaskets, pistons and rings...and repair the exhaust. If not satisfied with engine smoothness of lack thereof will check vibration frequency and reference Lycomings information to identify the cause...hopefully the engine is smooth or a static balance will solve the vibration problem..