[VAC] Re: Vintage Puller

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxxxx>]

Bob Kiger wrote:
> 
> It's a 352 and it runs like a dream.  I am counting on a good carb &
> vacuum adjustment, removal of the aftermarket air conditioner and
> bigger tires to get me from 10 mpg to 14 or 15 mpg without towing.
> 
> Also because my 66 Safari is so light and streamlined I am counting on
> pretty good mileage while towing . . . perhaps 10-12 mpg.  I will
> report in after finishing the project.
> Bob
> 
DREAMER!

No vintage carbureted engine will get anywhere near the mileage you wish
for because its too crude. The modern computer operated fuel injection
engines do significantly better because the computer can run each
cylinder as lean as will fire without pinging (the controls include a
knock sensor in the engine) and the engine size is minimized to closely
match the load. You can't get that fine a control with the carburetor
because the intake manifold is in the way modifying the mixture received
by each cylinder. Some intake manifolds run with a film of gasoline on
the surface to augment the evaporation at the carburetor jets.

Removing the air conditioner should gain maybe 1 or 1.5 mpg at the most
(disabling the air conditioner in my '98 F-150 by disconnecting the
clutch wire gains me about 1 mpg). Running HARD radial tires may gain 1
or 2 mpg. Larger tires probably won't gain a thing, but will confuse the
measurement because they will upset the speedometer and odometer
calibration. A lower numeric rear axle ratio or the equivalent in taller
tires makes the engine run slower. If the engine runs more efficiently
at a slower speed that may improve gas mileage. My 4.6L overhead cam
engine runs more efficiently at higher engine speeds so the drastic axle
ratio change I made had almost no effect on gas mileage.

I'm not even sure you can get the mileage you wish by dropping in a
modern 5.4L overhead cam computer controlled engine.

You can gain a little by using 50 weight engine oil in the manual
transmission and rear axle instead of the standard 90W.

You will gain more by running at 40 than anything else you do. Forget 75
if you want good mileage, loaded or empty.

Gerald J.