Gas Mileage

Can someone help me with my gas mileage[img]/phpBB/images/smiles/icon_cry.gif[/img]
I can't seem to get any. It seems like i have to go to the gas station 2 times a week, and thats just driving from home to school. And I keep my foot out of the throttle as much as possible[img]/phpBB/images/smiles/icon_wink.gif[/img]. my specs: 1970 Ford Falcon 302 stock cam-heads performer rpm intake 600 cfm manual choke edelbrock carb. 1-1/2 headers into 2-1/4 pipes thrush turbos dump before rear axle. My gears are stock 3.00 and c4. This is my daily driver is their any way to squeeze better gas mileage out of her.
Sorry for the length.
Thanks,
Joel

<font size=-1>[ This Message was edited by: Yellow70Falcoon on 4/24/03 12:04pm ]</font>

Well, first you need to tell us what your mileage is now, so we can determine if better mileage is even possible.

I don't know exact gas mileage, I'm guessing around 8-10 mpg.
(BTW Thats city driving)

<font size=-1>[ This Message was edited by: Yellow70Falcoon on 4/24/03 12:17pm ]</font>

Yeah, that's pretty crappy. Do you have a tuning kit for that carb? If not, you should get one, they're like $35 from Summit. It'll have all the jets and metering rods and springs you'll need. Try putting in a thicker metering rod, and a weaker step-up spring. I used to have a 1406 edelbrock, and it took a while, but I eventually got my 289 running about 14 mpg city/hwy.
[addsig]

If you want, PM me, I wrote an excel spreadsheet that converts rod and seat combinations into convential jet sizes. i have a carter afb 600, its the carb that edel used (rebranded?).

heavy, could you email that to me? waltbryant@hotmail.com
[addsig]

Your exhaust system sounds like it's too big for your combination and there's no back pressure. Although the 2¼" pipes are good for full throttle performance, downsizing the pipes down to 1.75" to the back of the car would help in the gas mileage department. A crossover pipe behind the headers with the smaller diameter pipes will also help. Disclaimer: These mods are for a stock 302 and would not necessarily be applicable for one that's hopped up or a larger engine.

What about your distributor and ignition timing? The vacuum advance needs to be working and curved correctly to optimize the gas mileage. Is the vacuum advance hooked up to the correct port on the distributor? Too much or too little ignition timing will also hurt gas mileage.

Taking gas mileage checks with every tank of fuel will give you a running average and will help you to evaluate exactly what changes you make in regards to gas mileage. Regular gas mileage checks will also give an indication over the long haul of any downward trends that could be occurring as well as evaluate the different brands of fuel. Definitely a difference in fuels when the compression ratio is marginal.

[addsig]

No offense, but I don't see why backpressure would help gas mileage. It can reduce the scavening effect in case of a large overlap cam (his cam is stock), preventing that fresh mixture goes directly through the exhaust pipe, but at low load, the scavening effect is limited anyway. It may have an effect on fuel consumption that I'm not aware off, but 8-10 MPG is almost twice as much as it should be. My 65 Mustang with a stock 289 gets up to 22 MPG at long trips (although it requires a light foot). If it only gets 8-10 MPG, then there's something wrong somewhere, probably with the ignition or the carburetor.

Joel-

I think the first thing you need to do is to determine what your mileage is. How else will you know if any changes have helped or hurt?

Is the engine tuned and generally healthy?

I would start with the basics, inflate tires on the high side, check for any rolling resistance (stuck calipers, dragging e-brake), eliminate excess weight, and do a full tune-up and filter change. Pay close attention to the carb and timing.

Hey Heavy, could I get that spreadsheet too? johnr_cote@hotmail.com

Thanks!

<font size=-1>[ This Message was edited by: JC on 4/24/03 8:14pm ]</font>

I have a dual vacuum advance, ones hooked up to timed advance and the other is hooked up to vacuum at back of intake. I hav 2-1/4 inch pipe because i plan to port the heads and get a good cam. I can't tell the ammount of degrees there is, there is only a little piece of metal by harmonic balancer with no numbers. I timed it on that piece of metal. Ill try to get more accurate gas mileage for you guys. Also can you e-mail that chart to me heavy: abrao@sbcglobal.net
Thanks,
Joel

<font size=-1>[ This Message was edited by: Yellow70Falcoon on 4/25/03 12:47am ]</font>