Small block Chevy Ideal Setup

Discussion in 'Chevy' started by Streffpilot, Dec 9, 2011.

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  1. Feb 26, 2012 #181

    4trade

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    Rob, i agree 100%.

    Beauty of mechanical engineering or experimenting is create something that is functional, fill that need and give satisfaction for designer. Like all in life....let innovative minds do their magic...and experiment´s. Without "out of box" thinking we all might think that globe is flat...
     
  2. Feb 26, 2012 #182

    Dan Thomas

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    Agree with all that. The key phrase there is "satisfaction for designer." Many fellows have tried to create a successful conversion but have not been satisfied with it. Many of them have flown those conversions, and the engine has let them down, sometimes fatally. We older guys, who have followed the auto-conversion thing for many years just want the newbies to understand that it's not a new idea, it's neither easy nor cheap, and it can kill you or someone else. I wish I was young enough and had the funds to do what Ben Haas is doing but it's getting a bit late for that. And I do know how to use a mill and lathe, though I don't have them anymore. The cost of that stuff--either the farming out of the machining, or the purchase of the machinery and learning how to use it so so you can do it yourself--also has to be figured into your project costs.

    I have often wished I had the time to take an old Navion, move the main gear forward and make a taildragger out of it, and put an SB conversion or a Geschewender Ford 351 on the nose. A poor man's P-51. Geschwender's conversions did work, and some Pawnee cropsprayers used them for awhile.

    But after the experience with the Subaru conversion, I know all about the endless fiddling and ultimate disappointment with the lackluster performance. The experimenting was fine for awhile, but after a while you just want to go flying safely and stop jacking around with the engine and redrive and all those systems.

    Dan
     
  3. Feb 26, 2012 #183

    stol

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  4. Feb 26, 2012 #184
    Dan, I know you mean well with your comments, but the building of ones own airplane should be a labor of love, an end to reach a dream. Its like warning a young man about the perils of dating a certain woman because you have had experience with her before, he is already enamored with her and your words fall on deaf ears.......... Will all of these experiences be successful? No, but its like every other venture in life,many will try so that a few will succeed. Personally I encourage everyone to try. Failure often breeds improvement and eventual success. As for the rate of failure, well its up to the individual to do everything possible to make it safe, to think it thru and to test beforehand as much as possible. Had the Wright brothers quit after their first misadventure, where would we be today? You are a knowledgeable and experienced individual. Why not give the benefits of your experience first hand as to why the Subie wasn't satisfactory and what you think would work better. It sounds to me like you really want to get back into building your dream aircraft.........Why not give it another go!
     
  5. Feb 26, 2012 #185

    GrizzlyV6

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    Rob,
    I seriously doubt if anyone has actually gotten mad over this. It is "frustrating" to hear those willing to argue about something that has already been proven successful. As far as "anti-engineering" goes, just how many real engineers do you think are contributing hear. I'm seeing people with opinions based on what - another opinion. How about those who sit infront of the keyboard and copy and paste an article they read somewhere on the internet then want to argue based on an article not real world experience. Here's a thought. If someone is going to come into this arena and "contribute" I would think that it would be best recieved if it were more than a copy and paste or an opinion with nothing to back it up. There are some on here who know things because they have actually built or are building something. Those with the stones to build their own redrive to go with an auto conversion I say do it. I like having choices. Hopefully when it comes to fruition, it can be done with the highest safety factor and without breaking anyones bank. Otherwise, it's just another overpriced product because it goes on an airplane. Did you know that Belted Air Power no longer contributes on forums because of all those self proclaimed engineers of everything who want to argue a point they know nothing about. So, I don't think anyone is angry. They're just frustrated with all the negetivity from those who really don't know.

    "Modify things that engineers create". You better be on your "A" game if that's your plan.


    Jim
     
    Last edited: Feb 26, 2012
  6. Feb 26, 2012 #186

    Autodidact

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    Dan has explained this a couple of times. To paraphrase, "The valves stems were too small and couldn't handle the heat at high power (high rpm) settings". This is why I value ALL commentary, it is all good food for thought.
     
  7. Feb 26, 2012 #187

    Dan Thomas

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    That was one problem with the Subaru, among others. That EJ22 had four valves per cylinder, and those cylinders are small, so the valves aren't very big at all. Since they're so small, and the continuous duty expected of an auto engine is only around 25 or 30%, the valve stems are small, too. They were under a quarter inch in diameter. If you've ever had a lawnmower apart, you'd see the same sort of valve. The exhaust valves get hot, and they dissipate their heat via two paths: through the valve seat when they're closed, and through the stem into the guide. Lycoming's valve stems are 7/16" diameter, giving them three times the area of the Subaru's valve (but the head is way bigger, too) and it's filled with sodium to expedite the heat transfer up the stem. The head of the Lyc's valve is very thick, as well, to wick the heat away from that sealing edge so it doesn't burn. It works; Continental's valves don't look like this and they burn more easily. The other major headache with the Subaru (and it applies to all PSRU'd conversions): The EJ22 engine develops its rated power at 5600 RPM. But if you try to run it anywhere near that for extended periods, the wear rate goes up and it burns a lot of fuel. If you lean it as you would the Lycoming or Continental, the valves burn. So you end up running it at 4600 or thereabouts. This becomes a big deal affecting in cruise speed: The propeller will be pitched to get redline RPM at full throttle in level flight. That gets the best range of performance out of a fixed-pitch setup. Now, when I reduce the RPM from 5600 to 4600, I end up with a sick cruise speed. The Glastar would cruise at 130 MPH at 2500 RPM with a Lycoming O-235; with the Subaru at 4600, it cruised at 105. See, the Lycoming is rated for 2700 RPM and you can run it at that speed all day; it's certified for that. Most operators will cruise at around 2500, a 7.5% reduction in RPM. With the Soob at 4600, it's 18% below its redline and we go much slower. Both engines, producing about 130 HP each, would give me about 140 MPH at redline in level flight, but the Lycoming is happy with that while the Subaru is eating up itself and your gasoline budget. Now, a direct-drive auto conversion setup would let the engine operate at a healthier RPM but we lose much of its HP capacity and suffer more pounds per horsepower. If we try to operate that engine at low RPM and high throttle settings we start to encounter detonation so we have to use decent fuel and retard the timing. Lycoming and Continental have to do that, too. Larger cylinders are more detonation-prone and the four-cylinder aircraft engine has a harder time of it than a V-8 of equivalent displacement will. Still, economy suffers when we have to retard timing and use more expensive fuel and the auto engine has little advantage over the aircraft engine other than smaller cylinders and perhaps lower CHTs.

    Cooling the Subaru was a challenge, as it is with most auto conversions, but I seemed to have got that right the first time. The only air exits from the cowling were around the exhaust pipes and through the radiator. Many guys stick a couple of small rads behind the cowl inlets; I used the stock car radiator and installed it at an angle with the top against the firewall and the lower edge about eight inches forward, with baffling along the sides and sealed against the cowl all around the bottom so the exiting air had to go through it. Max coolant temp in a sustained climb on a warmer-than-standard day was around 235°F, IIRC. Quite workable. But you need lots of cooling capacity and you don't want to create a pile of drag doing it.

    Mounting that Subaru was a first-class pain. All the decent mount points were at the front of the engine, not the rear, and the mount consisted of 17 pieces of tubing welded into an affair that reached all around the engine to grab those points. Many weeks went into the mount alone. I have seen various other mounting arrangements, some a little scary. One guy was using the oil pan bolts! That's not only a long way below the thrust line, but those are little short bolts threaded into an aluminum crankcase, designed to hold three quarts of oil and a two-pound oil pan, not a 275-pound engine, 25-pound prop, take maybe 500 pounds of thrust, and endure 9Gs in a crash. Nope. Dan
     
  8. Feb 29, 2012 #188
    Reply: I think thats the kind of information everyone is looking for Dan, and I for one really enjoyed reading it. Why do you think the Subaru can't make reasonably equivalent power to the Lyc at a low rpm? Was it smaller in displacement? The 4 valves per cylinder should be much more efficient at flowing air, even at lower rpms. I had heard rumors some time back that GM was toying with 4 valve heads for the LS engines, and I know there were some aftermarket (Arias $$$) 4 valve heads for the smallblock chevy. The use of smaller ports should help velocity at low rpms, and having 2 intake valves gives an overall larger intake (sq in) size than a singular valve.....so low end power and torque should be attainable. What do you think about it?
     
  9. Mar 1, 2012 #189

    Toobuilder

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    I for one am very happy the LS is a 2 valve, cam in block engine. The Ford modular (cammer) engines have almost no bottom end grunt, and many have attributed that distinct power difference to the 4 valve setup. It is not intuitive, but it certainly seems to be the case. Even in the 2 valve OHC automotive applications, you simply have spin the Fords much faster to get them to do anything.
     
  10. Mar 1, 2012 #190

    Dan Thomas

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    The Subaru EJ22 is a 2.2 litre engine; that's only 134 cubic inches. Tiny cylinders. That's why the Subaru has to turn at insane RPM to get 130 hp. The O-320 has 320 cubic inches and produces 20 more horses than the Subaru but does it at 2700 instead of 5600.

    For low end torque there are few substitutions for cubic inches.

    Dan
     
  11. Mar 2, 2012 #191
    Reply: I used to know all of the engines made by the big 3, but now there are a myriad of engines and I no longer attempt to keep up with them. The few Fords I have seen with OHC or DOHC seem to be ungainly in size and shape, and modifying one would be more expensive. On the other hand I like the simplicity of Chevy's 2 valve LS engines and the ease with which parts can be found for them.

    I'm not sure what GM had in mind as far as making a 4 valve setup work with the existing engine. The thing about a 4 valve is that having dual inlets means each passage and valve will be smaller which makes keeping velocity high at lower rpms somewhat easier. Then it can also cause more actual intake charge to be drawn in because the overall size of two intakes can be greater than a single intake. This is a good way to improve low rpm power and torque without increasing engine size.

    Although its not important to me in an airplane engine, another benefit would be additional flow at higher rpms and reduction of valve weight/valve spring harmonics. With a four valve set up , most manufacturers are probably going to tune their engines for the higher power range....but if someone is willing to purchase 4 custom made cams they can probably do the lower rpm range a lot of good. The other thing about all the additional hardware needed is the additional weight.
     
  12. Mar 6, 2012 #192

    Wagy59

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    Hmm..Well, I have a Ford long bed standard cab pickup with the 5.4 engine which is the longer stroke 4.6 triton engine. Now I'm not a fanatic about ford trucks or anything but I can tell you this...I've driven other ford trucks and have friends with ford trucks with the smaller ci engine and my truck will pretty much launch itself from a stoplight if you give it instant half throttle.. My friends with the shorter stroke engines dont have that experience....It's totally ridiculous how much power my truck has..I can be doing the speed limit by the time I'm through an intersection without even trying or straining anything and if I'm in traffic and have to punch it to avoid some idiot from hitting me it is totally ridiculous what happens..So you are totally off the mark in your conclusion that the fords have no bottom end punch .Mine is just a stock F150 with the long stroke engine and I can take **** near anybody off the line with it when I'm empty..i dont care what your driving..Not sure if mine is 3 valve or 4 valve..it's a 2000 model with 100,000 miles on it and still runs like new..and I have taller than stock AT tires too
     
  13. Mar 6, 2012 #193

    Wagy59

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    As usual, I hear many things I know are not necessarily true and just depends on one persons perception or conclusion based on misinformation, ..reminds me of our government
     
  14. Mar 6, 2012 #194

    Wagy59

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    oh..just realized Im being brutally honest..sorry
     
  15. Mar 6, 2012 #195

    PTAirco

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    I'm happy that you're enjoying the performance of your Ford truck, but subjective impressions like that are entirely meaningless when it comes to analyzing an engine's suitabllity for anything, not just aircraft engine conversions. What counts above all other things, are simply the torque and power curves. They don't lie. Saying things like "my truck will leave yours standing at a traffic light" really doesn't mean a whole lot. In a vehicle you're dealing with a ton of other variables; the weight, aerodynamics, the type and ratio of transmission etc etc.

    The first thing anyone should look at when choosing an engine to convert is the power curves, then the weight. Torque curves aren't all that important when you're fitting a PSRU; it can be tailored to fit. Any talk about long versus short stroke, 2 versus 4 valves etc is pretty irrelevant beyond the main two criteria of power and weight.
     
  16. Mar 7, 2012 #196

    Toobuilder

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    A high revving engine can be geared in such a way to move a heavy vehicle - so a drag race between a Ford and Chevy is not germain to this discussion. But if we're talking about hanging a prop off the end of an existing engine, I'd pick the LS over the Triton any day of the week. The simplicity of the cam in block and the low end grunt that a LS is capable of makes it an easy choice for me. Perhaps someone can dig up dyno charts and find out if the engines are indeed tuned for different powerbands. The Triton powered trucks I've driven may have been fast enough, but they sure do have to spin high to make it so (compared to the Vortec, anyway).
     
  17. Mar 8, 2012 #197

    PaulS

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    Torque and power curves are determined by the cam - all other things constant. Cars and their engines are designed to very different specs than aircraft. It only takes about 20 hp to cruise the freeway at 60 mph in the average family car so you do that with the throttle practically closed while at 1800 rpm. The power required to drive the same car ay 75 mph is about double or 40 hp. Both allow a very lean 14:1 air/fuel ratio but as speeds increase the drag of wind resistance and rolling resistance requires the hp to triple every time the speed is doubled which is why a car needs 600 - 800 hp to go 200 mph. A plane always needs a richer mixture (at altitude/density) than a car would. The cam in an aircraft engine would not do well in a street engine and would do worse in a performance engine. Using a street or performance cam in an auto engine for a plane would be a very bad thing unless the prop was spun from a reduction drive that could make up for the low amount of torque at low rpm.

    Paul
     
  18. Mar 8, 2012 #198

    stol

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    Last edited: May 5, 2012
  19. Apr 1, 2012 #199

    Streffpilot

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    Ben, had you ever considered a chain drive? Just came to mind. I will begining work on a SBC or LSx for the plane I build, but the space between the engine and prop has just become a blank space in my mind for the moment.

    Sam
     
  20. Apr 4, 2012 #200
    If you are going to use a Chevy, the benefits of an LSx type engine far outweigh the venerable smallblock Chevy. No knock on the smallblock, but unless you buy an aluminum version you will have to deal with more weight and smaller main bearings. You would be extremely lucky to find a used 400 (bigger main bearings) these days that was usuable.


    Most people want to use the smallblock because its cheap, but in the long run you will come out better with the LS.

    An aluminum smallblock will cost appx $4500 just for the block.

    A factory new LS alum block is $1000, $1800, $2700 and you can easily build a 415/427 cu in

    Used Alum heads for a smallblock will cost $600+ (and then need rebuild) New $1200


    Used aluminum LS1 heads can be easily found $100/$200
    (They should work fine if you run engine direct drive at 2700 rpms)
    (If you use a reduction drive then you can use the smaller cube in LS1 engine)

    Rotating assemblies, the LS will be a little higher if you buy quality forged parts, but not that much more. If you go with the really cheap cast crank stuff the smallblock will be cheaper here.


    You can save money by shopping around, but for the weight difference the LS is a better weigh to go. Remember its going to be on the nose of your plane and the extra weight may be hard to deal with....especially iof you add the weight of a redrive.


    Ben has a very nice Ford setup thats pretty light and has already proven his concept. Unless you are building a large airplane, there is only so much horsepower and weight that is viable.
     

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