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How difficult is it to build an engine from scratch?

Discussion in 'Mechanical & Technical' started by Furious Coder, Feb 26, 2012.

  1. I decided to go the software engineering route in college, but I've always maintained a love for working with my hands on actual physical things. I designed and built my own custom shed. I do most home repairs myself. I know enough about tolerances and materials science to be dangerous, but not useful.

    What I'm wondering is, how difficult is it to machine a solidly built, working engine from scratch? I know there are certain materials that are used in modern engines for their ability to resist wear, as well as expansion and contraction under heat. That fine tuning an engine design is a vast array of Operations Research, and Scientific Analysis. I also know that building engines in bulk requires quite a bit of material goods, and the facility to do so has some pretty extreme capitol costs. I understand this is why smaller run manufacturers outsource their engine builds to companies like Rotax.

    But if a person wanted to build, say, a 500cc parallel twin engine, or a 650cc v-twin engine, almost entirely from scratch (are valves just purchased, or are they machined?) what would they have to do, how long would it take, and what would it cost?


  2. From what I've seen, for the sake of dev time and costs, certain items are "off the shelf" and a design based around those items where possible to reduce costs. For instance, valves may or may not be due to their huge impact on head flow characteristics. But a piston or bore spec might be borrowed for faster time to running prototype.

    Cost is... ever rising.
  3. RedKat600

    RedKat600 Vintage Screwball Staff Member

    Start small. Build your way up. Even little guys like this one cost thousands just in materials, not to mention man hours.

    Valves? They can be either or. Typically it's cheaper to use valves already in existence. How many engines have you torn down and rebuilt? You really need to start there before you think about making one from scratch. That way you understand how everything works. Do you have a lathe? A mill? Any tools at all to accomplish this?

    To design your OWN engine, I would say it would take a few years, and then a few more to machine all the parts. Cost? I can only imagine in the realm of 5K or more. I mean, just the CAD software alone is what, 2K or so? Materials aren't cheap, and neither are one offs.
  4. Been there.
    Done that.
    I raced T/F bikes for a while. That process of going from Pro Mod to Blown Alki to T/F bikes forced us to build our own engines. All of it. Every piece. From scratch..
    We started out racing Kawasaki's and changed over to Suzuki's in about 81. The first thing we did was design and build a 2 valve head to replace the 4v one. This was to get the flow rates in the ball park of what we needed but in reality, it was to get the bore spacing right in order to make 1602cc which was the NHRA and FIM limit for 2v 4cyl motors. That was important so we could get proper head gasket sealing that would live for a pass.
    All the power is made in the head so then you have to start thinking about cases that won't fret under load. We built ours out of a 450lb block of 7075T6 aluminum.
    Then comes a crank and rods....
    We got to the point where we were building our own fuel injectors. Rus Collins is a pretty good friend and gave us a bit of good dirrection...
    This of course will require you to have access to lots of time in a machine shop. That will require you to have some skills....Nobody is gonna turn you loose on their machine tools if they dont' know you aren't going to crash them. And even then...they aren't going to turn you loose. So you can go buy your own. Figure on about $1.5 million to get started. You'll need a couple of machining centers and a turning center. You can farm out the grinding.
    You'll need to become VERY proficient at Solidworks or ProE or something along those lines. Then you're going to need to learn Mastercam or something like that in order to program the machines.
    You'll need a building to house this in and some employees to do some work that will generate the money to enable you to persue this sillyness...
    So...Hows yur math skills?
  5. And here's Jim with reality! :)
  6. +1
  7. I worked at a place where we built model airplane racing engines completely from scratch. These were four stroke twins and singles, up to 270cc's. We didn't make the carbs, the fasteners, valve springs, or the cam drive belts, but everything else was made in house. It's a lot of work and a lot of engineering. We had close to half a million dollars in machining equipment.

    It's not too terribly difficult if you want to build something small and simple that just runs, but that will give you an idea how much work there is involved. If you want to build something larger that actually makes some power, yeah...

    Good luck!
  8. You'd better have a pretty firm grasp of metallurgy as well.
    There are wear issues in cam faces, oil pump housings, bearings...Lots of stuff.
    Valves aren't anywhere near as simple as they look either.
    The vast majority of them are two piece the furnace welded and then finish ground. The trick it determining where to put that weld so it's not on the bend moment of the stem/ head. The head is doing some pretty serious moving around as it rises and seats again. One of the advantages of four valve motors is smaller valve tulips....just for that reason.
    You're going to need to know something about rod length/ stroke ratios. In addition to Bore/stroke ratios so as to fully understand how your head will fill your cylinders at a given in/Hg. Think flame propagation.
    The act of designing and manufacturing an engine of any complexity is really a team sport just as an expediency of time if nothing else. You simply won't have enough time in your life to learn everyhting you need to get it done properly. It is a HUGE undertaking. We had about 30 people in the shop working on it. This is also the reason racing is an evolutionary process.
  9. Rippn

    Rippn Human Race Qualifier<br>FREE and clean

    I think 1951 is being "GENTLE"...
    divorces, insomnia, physical breakdown...mental breakdowns/health!!!!!!!!!!!!!!!!!!!
    mistakes, material flaws, accidents... revisions, loss...
    a "perfect" omelet, made from Bird of paradise eggs... would be WAY easier...
    FREE and clean, Ripp'n
    AlbatrossCafe likes this.
  10. I can't even imagine-just the bearings.........oh and dragracer-imma need to see your stuff!
  11. There's a certain level of, ahh, commitment.
    On blower motors, the bottom pulley has a center hub that is buffered with a rubber like material. Every bike and even the tune is effected by the durometer of that material. Get it a little too hard and you'll rain blower belt teeth for a thousand feet...
    I took my family with me to Europe when we went over to race. That makes it a LOT less stressfull.
    But it's a team effort.
    I know a couple of people that have built sprint car engines from scratch.
    I know another guy that does incertable combustion chambers for Offy flatheads. I have the cad models around here somewhere. I did the cores for the castings.

    Bearings are an interesting thing. We use bearing hardness to soften the hit to the crank and thus let the bike hook up a little easier...
    Ain't tuning fun?
    Last edited: Feb 26, 2012
  12. This model engine was featured in a R/C magazine I subscribe to this month. Pretty cool!
  13. DGA

    DGA Moderator Staff Member

    Like Jim said...extremely hard and extremely expensive.

    If I were you and want some hands on experience, try putting a stock engine together from the first to last bolt back to factory specifications. This alone will teach you a lot. Than do about a dozen more of various designs to further familiarize yourself and gain experience and knowledge. By this point you will understand a lot better what goes into an engine, but will still be very inexperienced to start your own design. This alone can take many years if not decades, and that is if you dedicate yourself to the craft.

    In another words, try crawling first before you attempt an Iron-Man marathon.
  14. PeteN95

    PeteN95 Moderator Staff Member

  15. KillermondoDude

    KillermondoDude Intellectually Sphinctered

    Late Apexes father built a rotary motor from scratch (Lathe Mill and Drill Press if i remember correctly) with a lil farming out he would be able to tell you what would be involved
  16. mjn

    mjn Forum Admin Staff Member

    Funny.. I was thinking the exact same thing while reading this thread.
  17. have you thought about steam for your first go-round?
  18. buy a junked 928s4,(cheap) tear the motor apart and rebuild to spec. go from there.
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