<VV>Leaning out the midrange

[Padgett]

> > Readings obtained indicate the F/A mixture is consistently rich
> > (11-to-12-to-1) in the cruising range. I've gone as lean as I dare with 
> the main  jets
> > (.049s), but jetting does not appear to significantly affect 
> midrange  mixture.

Should. Have you checked that the PE needle is in both carbs and it drops 
all of the way down ? Is quite possible that you could get better economy 
from an earlier set of carbs without the PE circuit.

One was missing on my 110 when I bought it and when replaced, a slight lean 
misfire (may be due to some head issues) at cruise began. Replacing the 
stock .050s with .052s cleared that up The other thought is are you getting 
full mechanical and vacuum advance ? At a high vacuum cruise, the flame 
front expands the slowest, and you need more advance. .049 is not that lean 
(and was stock on some Corvairs) to go 10% leaner than an .050, you would 
need at least an .048.

If really serious about MPG this might be a good time to invest in a 
quality EGT readout since as you go lean, the EGT rises so is better than a 
standard O2 sensor for adjusting in the 16-17:1 range. Can also get close 
with a manifold vacuum gauge you can read to an inch but when running at 
the limit I would want to keep an eye on the EGT. CHT will tell you some 
things but will not react as fast as EGT.

To run at the lean limit, I would also suggest a Pertronix II ignition and 
coil and plugs you can gap to .060".

Running for max economy takes just as much effort as for max power (and 
some things are quite similar) but the H series of carbs were not 
Rochester's finest - the later primary rods and triple venturi of the M 
series was much better for control and while the (M)2M(E) did not have a 
lot of CFM (about 180), one on a center mount might be the way to go since 
the long tubes would help atomization. Of course the real answer is direct 
port injection.

Padgett