jeep97tj wrote:detroit diesels have been around for ever, Iv worked on alot of drill rigs that use them, they were super charged only. We had an oshkosh service truck that had the supercharged detroit plus twin turbos, and that think flew. Never have i heard of a 2 stroke petrol with overhead valves though, so its news to me

jeep97tj, I have in my possession a two stroke with............. wait fer it.....
......

a ROTATING CYLINDER LINER which drives the crankshaft,(or what is commonly refered to as a crankshaft)in this case, there is no crankshaft as we used to know it.
It also has NO VALVES as we know it, but a hollow cylinder which also spins and positions ports cut into it to allow egress/ingress of gasses.
The engine it'self, is built for model aircraft and in the 10 cc capacity, though there is no reaosn whatever, could not be scaled up into larger versions.
I also have four stroke engines which run on TWO STROKE FUEL, that is the engine has cam shaft, pushrods,valves ect but runs on a mix of synthetic oil and methanol,(two stroke mix) these engines rely on the oil content of the fuel for lubrication, AND are specifically designed with PISTON BLOWBY.
A level of blowby that if it was present in your car, you'd junk it pretty quick. However, it seems to work admirably well in these engines.
They are available from 2.5 cc's right up to four cylinder 50 cc's and even more, like a radial five cylinder or seven of 100 cc's.
Now, the crux comes with these engines that are all designed to run on methanol which is expensive (last I checked, in excess of $30 20 litres)
many are converting these engines to standard petrol two stroke mix just as you run in your conventional lawn mower to cut operating costs, increase power and run cleaner.
Modifications required are inserion of spark plug, high tension coil/battery pack to operate same and a pressure operated carby, all avaialble after market.
Thus, at the end of the day, we have an engine with two valves,pushrods,camshaft,followers running on two stroke fuel mix.
We also have simple two stroke engines with port transfer or reed valves, running on the same methanol mix also converted to petrol by adding spark plug and ignition pack/carby thus basic two stroke engine.
Capacities ar anything from 2.5 right up 150 cc and more, with radial configurations, flat fours and flat 6's even fours and 6's twins in line.
And last but not the least, recently turbines have made a big impact into the scene, these turbines are simply a Garret turbo compressor fixed to a shaft with a turbine wheel attached at the opposite end, inbetween is a combustion chamber which has fuel and compressed air injected into it, ignited via a spark, once alight, it's self perpetuating and increases speed with increase of fuel, if allowed to, it will speed up until self destruction occurs.
Many people have built their own and been very successful, in my case, I bought a commercially produced one made in Perth W.A. which I still have.
If it wasn't such a muck around, I'd post some pics for all to see what we're talkin about, but I can't be bothered with the drawn out process.
Instead I'll direct you to some sites where you can see for yourselves what I'm talking of.
http://bennettbuilt.com/index.html
http://www.gtba.co.uk/index.htm
http://www.gasturbine.pwp.blueyonder.co.uk/newpage.htm
http://www.rc-airplane-world.com/model-jet-engine.html
http://www.justengines.unseen.org/mvvs.htm
http://www.webra-austria.at/index1.php?lang=EN
https://www.nelsonhobby.com/prospark.html
http://www.aero-sports.com/airhobbies/twineng.html
http://www.tjt.bz/
This is just a scratch of what's available, a little research will soon illuminate literally hundreds od such manufacturers throughout the World.
Anyone who is mechanicaly inclined and simply loves such devices wil certainly enjoy the lot. Enjoy.