Hello, everyone!
Small engines naturally make more hp per liter. If you solve the engine
power equation, holding everything constant except a "characteristic length
= L" then you will find that power output varies inversely with L. In
other words, given identical efficiency, a smaller engine will put out more
power per liter than a larger one.
All engines are more powerful now. there are a variety of reasons for this
but I believe that the most important one is metallurgy. Parts can be made
stronger and capable of withstanding higher temperature / surface
pressures. Camshafts can be more radical (higher surface pressures) and
engines can be spun faster (stronger, lighter parts) so engines make more
power.
The second most important change, again in my opinion, is oil quality.
This has the same effect as better metals, allowing higher surface
pressures, more radical cams, higher rpm.
The last big change is the move to more compact combustion chambers. It
used to be believed that the secret to big power was big valves so people
developed race engines with wide valve angles and high combustion chamber
roofs. To get the compression up, they then installed domed pistons.
Because of this, flame travel lengths were long and quenching was high so
combustion efficiency was low. Modern engines have very compact combustion
chambers that make the most of the fuel / air delivered.
There is a lot of talk about the correct dizzy position. When I used to
rebuild a lot of engines, I never worried about which way the rotor was
pointing upon assembly. I just threw the dizzy on and, when the time came,
found TDC and adjusted the dizzy to where the points were just opening. I
then put the number one plug lead in the hole over wherever the rotor was
pointing and went on from there. Does this make me a DPO? Maybe but the
engine doesn't care one bit as long as you can time it and the order is
right. If I couldn't get enough advance or retard (usually due to the
vacuum advance can hitting something), I just moved all the wires one hole
in the correct direction and started over. We had over 20 motorized
devices around the farm / shop / construction company, all of which were
bought at auction and none of which we had manuals for. You just used
torque settings from the Machinery's handbook and winged it.
When I owned the Spit**re, the WORST change that I ever made was to
install an electric fan. The quite loud noise was entirely out of
character with the car. I was alway looking for low flying jet aircraft
when it went off. I tried putting acoustic foam under the bonnet but that
didn't help much. The sound is part of the driving experience, don't ruin
it, in my opinion.
Regards,
Bill Eastman
61 MGA with fan blades just waiting to free themselves, I am sure.
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