Since returning form California I have been focusing entirely on the new bike, the “Iron Triangle”. It will be powered by a new engine I am building, which I have nicknamed the “Mini Stroker”. I will attempt to explain why I named it that: It is a hybrid of a Harley Evolution motor (built from 1984-1999) and a Harley Twin Cam motor (built 1999-present). In a nutshell, what I am taking from the Evo are the case mounting system, the bore and stroke, and the wrist pin. The Twin Cam parts are the cams, oiling system, heads, and crank assembly. The reason for this is because I feel that the Evo bore and stroke combo is superior, in many ways, to the twin cam. However, the Twin Cam is a far stronger motor (due mostly to the robust flywheel design) , and has a far more reliable oiling system.
So, since a first generation Twin Cam was 88 cubic inches (3.75″ bore by 4″ stroke), and an stock Evo is 80 inches (3.5″ bore by 4.25″ stroke), that means that in a Twin Cam crankcase I have increased the stroke from stock, making it a “stroker” motor. however, due to the reduced bore it has less displacement than a stock Twin Cam- hence “Mini Stroker”.
In addition to all this, I also changed the cylinders from stock cast aluminum with an iron liner to billet ductile iron. This is heavier, but also far stronger and more dimensionally stable under heat. In other words, as it gets hot it doesn’t change shape as much. This means tighter tolerances all around. I also used a head/ base stud pattern for attachment to the case and heads, instead of the thru-studs an Evo or Twin cam would have had. Again, stronger. In order to make the Twin Cam heads work with my new bore and stroke combo, (as well as a copper o-ring head gasket) modifications had to be made. I wanted to reatain the stock Twin Cam combustion chamber, but it needed to be reduced to 72 cc’s of volume to achieve my 10.5-1 static compression ratio. This meant decking (milling down) the heads significantly. In addition, the new flange system was milled into it to accept the o-ring gasket.
Ok, enough about all that, here are some pics:
I was lucky to have two trusted advisers here to help, my main man Alex Lerner from SL NYC in Queens, and Satya Kraus from Kraus Motor Co in northern Cali.
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This is the “cam-plate”, the component that supports the cam shafts, routes oiling, and holds the oil pump.
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Installing the bearings on the flywheel
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Checking the endplay on the left case half
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Completed short block
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Here is completed frame. All chromoly, all made here at Efab
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closeup of front motor mount
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More to come!
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