>
> Wow,
> Lots of good letters have just been written on this subject.
> ( Chip Old, Roger Garnett, William Woodruff )
>
> Randy Wilson, I think you misunderstood me. I was making a simplified piston-
> cylinder model based on a flattop, two-valve setup like that commonly found
> on older English cars, hence the math was setup for a Triumph 2-litre six.
>
I fully understood this. The main point I was making is that your calculations
assume the new overbore pistons have the same pin to crown height as the
originals. The changes in compression caused by the volume change is so obvious
that I would find it hard to believe it got past the piston designer.
(off subject musings about fluid dynamics deleted :)
>
> I guess I wasn't too clear on the 'compromise' resulting from milling the
> head. Torque is calculated from Pressure*Volume, and while milling the head
> increases the Pressure, it decreases the volume. Hence the compromise.
>
Ah, okay. Rough translation = There is no substitute for cubic inches.
More importantly, it appears you are viewing the V from the finished end. I
was thinking from the starting point; total cylinder volume. Makes sense.
As far as hard facts in all this, I have none. I've never measured the crown
height of stock vs stock-overbore pistons. Any engine that I was building
with performance in mind, and required an overbore, did not get stock pistons.
Randy
|