<VV> Fuel Mileage with a Tweaked Carb

[Craig Nicol]

Mike wrote: "... By tweaking (lowering) the float levels, I've been able to
maintain (at around town & cruse speeds), between 14 to 15 A-F ratio. The
car I've done this with is a 110 with PG and dual   exhausts. I've installed
in-cockpit, dual wide band digital instruments (by Innovate), so I can see
what is happening under all conditions, side-to-side. Before float tweaking,
even after reducing jet sizes to under OEM speck, I could never get the
system to run leaner than about 13.5..."
 
The following relates to the car mentioned above: just returned from my
semiannual trip to the Florida Keys. Running between 60 to 70 mph
(frequently higher) I recorded 22 to 23 mpg with the A/C, and 25 to 26 W/O
air. This car has a high stall speed converter; so, with an OEM converter,
mpg would be better, I'm sure... Still, not bad.
 
Once I check my notes, I'll broadcast the float settings. Again, this car is

Safeguard equipped with initial timing set at 18-degrees. Careful with
leaning if you are not using a knock sensor system. 
 
Mike Mauro

Craig replies:
You da man, Mike! I've wanted to do this for years but never got around to
it. The stock carbs are jetted rich - I've often wondered about folks who
put in #53 jets "for more power" since the stock calibration is already at
the "max-power" AFR.  FWIW, 14-15 AFR isn't "Lean" except in relation to
stock.  15.5 (or even 16.5) is considered the AFR for "Max economy" and
beyond that is considered "lean". EGT (and NOx) goes ballistic somewhwere
above 14:1 so above that point it pays to monitor EGT with a pyrometer.
1250-deg F. is considered the max for a diesel engine. Does anyone know what
the limit is for a gas engine?  Are you doing these adjustments on the
"high-swirl" engine you built a few years ago?  If so, it should tolerate
15.5 or more AFR. What size jet are you down to, 48?  Are you using a 65-6
power-valve carburetor so max power isn't compromised?

Great work - you're a pioneer now!
Regards, Craig