On 10/05/2020 22:05, John Rumm wrote:
On 10/05/2020 16:47, AJH wrote:
On 10/05/2020 15:49, Weatherlawyer wrote:
On Saturday, 9 May 2020 16:22:34 UTC+1, JohnÂ* wrote:
On Sat, 09 May 2020 04:48:43 -0700, Weatherlawyer wrote:

How does the first Ford compare to the latest iteration, that is how
does the 1930's environmentalist compare to the 2020 version?


The original ford V8 engine was a side valve engine.

That's good to know. So how was the side valve replaced by a more
efficient high compression engine?
And why?

Once the block casting was sorted it wasn't a big step to put push
rods where the valve stems were and and OHV head on, this would have
given an immediate increase in compression ratio as the empty space
the valves previously opened into could be eliminated, and the
relationship between thermal conversion to power is a straight line
with compression ratio.

What I don't understand isÂ* what, other than higher engine speeds, the
advantage of overhead cams give in relation to thermal efficiency?

Reduction in valve mass and spring tension required, plus improved gas
flow (inlet and outlet) since your manifold design does not need to be
compromised to avoid the pushrods. (its also supposed to be easier with
double overhead cams to implement 4 valves per cylinder)




Yes but these are all to do with volumetric efficiency (getting more
fuel and air into the cylinder), including the periphery of 2 inlet
valves being bigger than one large one.

Why should this increase thermal efficiency to give more miles per
gallon if you might be happy with a modest performance and more mpg?

I can see the point about the mass of valve gear and losses in
compressing the spring but surely you get most of that back as the
spring pushes the cam load back round.