First of all thank you for your interest. I am always interested in aviation books because flying is my first love. Having said that I have a lot of problems with engine as it came in the kit. Honestly I had no intention of making this an accurate replica of the real thing and took a lot of liberties with it. Bluntly, Tom Daniels also took far more liberties than I and as such left me with little opportunity to bring it up to an accurate representation of the real thing.
First off, I suspect that it is a 1:72 scale engine out of an aircraft kit. The real engine is about 65" inches long, almost 5 1/2 feet. Scaled out, that would mean that the engine should be close to 2.7" long in 1:24 scale. This model engine is nowhere near that length. It is just under an inch long. This would make sense for a 1:72 scale
On top of that it has a lot of peculiarities specific to aircraft engines of the era that would make it very unsuitable for an automotive engine without a lot of modifications. First it that the intake air runs through the crankcase to warm the air. This is an anti-icing measure that robs power from the engine. I modified the engine with a side mount intake that would theoreticaly go into the pair of updraft carbs just to give it some semblance of reality.
Second the valve system is top mounted for ease of maintenance as was the custom of the period. This also helps with the compression release access used to start the engine by “hand propping it”. Something you just couldn't do with and engine of this size with a crank. There had to be a starter somewhere on this piece and there is no provision for starter anywhere on the model. Building an accurate valve train was just a waste of time in my estimation.
As far as the dual magneto/plugs this is something that is almost exclusively used on 4 cycle aircraft engines. Dual ignition has two purposes. First and foremost is to provide a backup in the event of the failure of one system. It matters a whole lot more in an aircraft if the electrical system poops out than on a car. It also improves combustion marginally but that can also be achieved with better plug location on a single plug engine and would not be considered worth the additional weight and complication on a hot rod.
So, for those who are interested in seeing an accurate portrale of a Mercedes D III engine, this is not the place to look. This engine is so bastardized to begin with that I felt compelled to improve it visually and ignore the original engine. Perhaps someday I will have the urge to build the real thing, but today is not that day. This engine is more about improving my skills as a miniature metal worker and making something that looks good. Artistry was much higher on the priorities than accuracy for this build.
Edited by Pete J., 22 February 2013 - 04:52 PM.