I mentioned that the oversquare engine will generate less heat due to the shorter stroke causing less friction. It also transfers the heat to the cooling system more efficiently because the larger bore cylinder will expose more surface area.
This is also a detriment to the efficiency of combustion in the cylinder. The flame has to spread across a larger surface. A greater portion of the combustion heat/energy is being transferred to the cooling system, rather than being converted into work. And there is a greater loss in pressure per angle of rotation with a shorter/wider cylinder, regardless of rod ratio.
It seems, in my limited understanding, that any benefits of going oversquare, just to gain larger valves, would be negated by the less efficient combustion characteristics. And oversquare cylinders make less efficient air pumps.
So in a naturally aspirated motor, I am going to build it undersquare to capitalize on the efficiency of the tall/narrow cylinders, both as better air pumps and as offering better combustion characteristics.
The small bores/valves can be ported to flow PLENTY enough for a naturally aspirated 359ci (6.0L) motor. TEA stage 2 flows over 300cfm @ .600, which will do just fine for anything less than 7.0L spinning at less than 7k rpm's.
Any thoughts? Am I missing something entirely? The obvious trend in OEM engines is oversquare, unless you count transverse motors which tend to be undersquare for packaging reasons.
You can't really say reliability or service interval is a determining factor in this case due to the fact that there are a lot of high mileage OEM motors still on the road with 4" stroke crankshafts.
And with compression ratios constantly on the rise, you would think that a longer conrod would be preferable to slow the piston near top dead center for less detonation issues. Undersquare engines tend to have longer rods inherent to their design.
So if you can achieve adequate air flow with smaller valves, what is the advantage of being oversquare? I should say that we are staying below 7500rpm's for the sake of this discussion... I have no interest in tickling 10k rpm's.
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