I started keeping track of my MPGs since my last oil change. As you can see my gas mileage could definately be improved upon. Are there any things I can do to my carburetor that will help out?
BTW- I am running a Holley 600 on a L69. Engine is stock. I've put on dynomax catback and removed smog. I was thinking about putting in a non-cc q-jet. Would this help me with my MPG as opposed to my Holley? Are there any non-cc qjets I could find at the boneyard that might already be jetted close to what I need for a 305?

 

does the car run well? do the plugs show you're running rich at cruise? rich at WOT? perhaps modifying the jetting would help (lean it out).

also, you have a working vacuum advance distributor? 50ish degrees at cruise?

is your EGR hooked up and working? EDIT: I see that would be a no, if your manifold has the provision (doubt it does) it would add an MPG or two....

A non-cc qjet from a mid '80s cutlass is what I used, and it was jetted for an LG4, worked perfectly. I think a q-jet may help a bit on the fuel mileage, can't hurt to try it out I suppose, it'd be a cheap test.

 

The car runs very well. The reason I don't have a q-jet was due to an unfortunate fire that burnt much of my wiring harness. I have provisions for EGR, but have it capped off right know- I'm not sure if I could get one to work again. Plugs look good. I do have a vaccum-advance distributor. Not sure about the settings are at cruise but at idle it is set at 8*. The car is running great, doesn't seem to be over jetted or anything like that. I was thinking putting a non-cc q-jet might help a little bit b/c of the smaller primaries and the use of the air-valve. I have an extra spreadbore manifold in my garage I could put on to match it. What do yall think?

 

You're not really looking too bad. Are you locking your converter? If not, this would have two advantages: slightly better cruise/highway mileage and trans longevity.

I'm running a stock 160,000 mile LG4 (w/ccc-qjet) and average around 22 but get up to 27/28 on highway trips.

 

i can pull about 24-25mpg out of my LG4 on the highway, i'm hoping it will improve now that my EGR works again.

 

The EGR benefit to MPG during cruise is secondary. Exhaust gas entered into the combustion chamber lowers combustion temps. These lower temps allow the introduction of more ignition advance. It's the additional advance that provides the mileage increase. If your EGR is not working you may sometimes notice a slight pinging during part throttle/low load cruise-especially in later fuel injected vehicles. ECM will see this pinging and pull out advance, lowering MPG.

I'm not certain our older CCC-Qjet ECMs took advantage of this benefit of EGR and added the extra advance. Maybe someone knows better?

 

Yes, I do have lockup on my torque convertor via a vaccum switch, it actually works very well. I guess the main thrust of what I'm trying to find out is whether or not a q-jet with the smaller primaries in the front will help out with MPGs at cruise, I've pretty much given up getting any good MPG in the city.