well since it sounds like you are into racing then I would suggest drawing a 2 cycle motor that "functions" and then animate it. When done move onto a 4 cycle and add in the valves. Learn to run the animation and interference detection built in apps.
Also start reading into how machinist read prints...often times it is much easier to draw the part than to effectively communicate to what specifications it must be made to.
the final thing would be to learn to insert parts based upon reference points and ultimately the final accuracy of a bunch of moving parts will improve and be easier on the computer
i teach cad at night at a local university for my 2nd job