Ancient History

[Robert J. Harris]

Am new to this mailing list, but have been thinking about this for years. 
Several years ago I drove a 1966 Chevelle with a 350 V-8 that had
neck-snapping acceleration and excellent all-around drivablity. Belonged to
a young machinist I took an aluminum head in to have a crack welded on. 
Asked his secret - and was amazed.

Seems he took an older, off the shelf Hilborn mechanical fuel injection,
modified it slightly and put it on the engine.  Hold the objections, rumors
and myths till I finish.

He drilled the heads so that the untimed variable flow injector sprayed
directly on the intake valve from the back side of the valve pocket.  What
was lacking in mechanical sophistication was made up in simple physics.

Liquid fuel does not burn - period.  It must be vaporized before it burns.
All forms of carboration - including fuel injection - atomize the fuel
hoping enough vapor will be formed to start combustion so that the heat and
violence of combustion will finish the job.  Power and fuel efficiency are
directly related to how well that is done.

Gasoline and air, when mixed has an broad range of combustion, from a 12 to
one mixture for power to a 19 to one mixture for economy. The secret is how
well it is vaporized and atomized prior to combustion.

>From a vaporization point of view, gasoline has components that boil
(vaporize) at temperatures from room temp to about 540 degrees F.  Smokey
once built and patented an engine that heated the intake mixture to this
point and made amazing power and efficiency for NASCAR engines.  The fuel
-puddling on an intake valve has its temp raised several hundred degrees -
without heating the incoming air charge. More fuel vaporized probably than
even the most modern injectors achieve - by merely dumping it on the
hottest spot in the intake system. Plus fuel vaporizing had to cool the
valve - so even less heat added to the air mass - meaning a denser fuel air
charge to the cylinder.

Next, from an atomization point of view,  the unvaporized gasoline
components and fresh fuel were injected at the point where there is the
maximum turbulence and violence in the air flow - the seat of the intake
valve.  Cold dry air to the port, fuel in at the valve seat itself - no
drop out problems period. Not mechanically possible to mix it much finer.

With simple tuning and good physics, this crude system worked very well
indeed. The extremely high quality fuel-air charge made up for much of the
mixture variations that this simple system had and made a very responsive,
decent fuel economy street engine.

No moral to this story, just food for thought.  On my DIY conversion I am
thinking about, I plan to put my injectors in the valve pocket if at all
possible for all of the above.  Only thing better would be to steal a
diesel injector and squirt the fuel directly into the chamber against both
intake and exhaust.