RE: RC Car Actions "How to port a Nitro Engine"
I have a degree wheel...well, my attempt at making one. That round "dish" thing that the parts are sitting in when I took the pics is a lid to a tuna can in which I glued a circle with degrees marked to 5degree increments. It's horribly inaccurate, I attempted to take the K4.6's measurements with it and these are the following results I measured (stock timings):
Crankshaft induction: 193degrees
Boost port: 106degrees
Lateral (Schneurle) ports: 114 degrees
Exhaust port: 154degrees
Degrees ATDC before crank induction port opens: 223degrees.
My error factors are at least plus or minus 5 degrees since I could not draw the wheel to any high accuracy. Also, I estimate another plus of minus 2degrees for my manual drawing inaccuracies and how I placed the ruler on the paper when I was drawing the wheel.
This is a horrid plus or minus 7degree error margin.
Pro Twister Mods in the other porting thread posted some tools I could use to make a more accurate degree wheel; I have one on order, but in the mean time, I am going to try to hit the local hardware store and see if they have someting just as suitable. I might also hit the local print shop; they carry all sorts of stencils, slide rules, and just might have an accurate degree disc.
Once I have the degree wheel, my next odstacle would be to make a reliable jig so I can mount a needle to point at the degree graduations with accuracy.