Today we will be looking into the theory of the power behind the engine and how to get the most bang out of a given engine.  There are a few things that need to be outlined first. One is that an engine that revs higher has a greater potential for power – to a point.  Two is that shorter stroke equals higher revs.  Three is that hemispherical combustion chambers are the most efficient.  And four is that a balanced motor is a balanced motor, regardless of any preconceived notions of piston weight and rotating mass.

Now that we have the prerequisite conditional assumptions out of the way, we can get on with the theory behind the maximum power output of an engine.  Common engine build involve the finding of an adequate producion block and modifying it through a stroker kit and a bore job, coupled with a set of aftermarket heads to produce the desired combuston ratio and a power adder as desired – a.k.a. a blower, supercharger, nitrous oxide injection, alcohol injection, and the like.  This produces some problems however.  One of these problems is that there are only so many combinations that one can obtain with parts off the shelf, the other is that there is a serious detriment to the power output possible of being attained.  Most high end engine builders then machine a longer block with a larger bore that keeps the crankshaft throw to a minimum; reference pro stock cars.  If one were to take a stock 426 Hemi and put it alongside a pro stock Hemi, you would notice that there are a few differences, mostly with the heads, but also the block is longer by a fair amount.

The real difference here is the maximum power output, as there is only so much that an engine can be bored.  If one were to start machining on a block and bore the cylinders to whatever desired size to obtain a higher power output, one would run into a thinning of the cylinder walls, causing a distinctive weakness in the engine design, as the cylinder will not be able to maintain the pressures required, resulting in a blown out wall, possibly more damage.  To rectify this problem we need to elongate the block.  This is highly expensive and specialized due to the machining and casting involved.  It would also require the forging/machining of a set of heads to match the block.  In short, this is not the everyday engine build but it is necessary for the pursuit of power.  If one were to combine an engine with the firing order previously discussed (http://bricrods.com/2009/06/engine-efficiency/) in this particular lengthened design, and a set of high flow custom Hemi heads with a pair of plugs per cylinder and a well designed intake (which we will get into in another post) one would have the makings of a serious contender on any front.

Just as an aside, there would be massive potentials for torque in this engine as well.