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Discussion Starter #1
Ok here's my problem... I fix all my problems. The car is on the road, everything is great. Time to figure out how many miles per gallon of fuel I get. So I do the math and it comes to 7.5 miles to the gallon. That's really horrible, being that my last engine, a 351W, got around 14 MPG So my smaller engine [302] now gets worse MPG. What's up with that? The car runs perfect as far as I can tell. What can I do to get a better mile to the gallon? What could be wrong? What is the normal MPG for a strong running 302 with 100,000 miles on it? - Chad
 

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Chad, somethings wrong with 7.5mpg. You wernt rodding the piss out of it were you? Refresh my memory on your car, it's fairly stock isnt it? mm
 

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In response to your question about normal MPG, I had a 289 w/ an Edelbrock Performer manifold and a 600cfm carb everything else was stock and I averaged 15-16 MPG.

__________
'67 XR-7, 351C 4V
 

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MPG

wvcat gets 12 mpg on the highway with an AOD, 3:73's and a big cam ([email protected]) don't even ask about around town. Put it this way, my f150 gets better mileage. Seems like somethings wrong there Chad. Are you positive on your mileage numbers? How many miles per tank do you get?
John
 

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Discussion Starter #6
Oh yeah I'll include some more info about the engine/drivetrain : 302 completely stock, but it's got an automatic choke - that doesn't work! 3:1 gears in the rear-end. It needed some transmission fluid so I put in 2 quarts... I haven't found out exactly how many miles to the tank because my fuel guage doesn't work, but in the course of driving 90 miles, I put 12 gallons back into it - 90 / 12 = 7.5 -Chad
 

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7.5?? ouch, when my 351 was stock ( with a 2bbl and a single exhaust ) it got about 8 mpg or so. with an FMX and 3:1 gears. with the mods it has now ( 600 Holley better ignition performer intake headers duals flowmasters ) i get ALMOST 11 mpg on the street and can scratch 13 on the highway. i only use premium in it, so i spend alot either way. (gas is down to 1.23 here in Cali for premium now!!) so 7.5 in a 302 is not all good.
 

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Is it possible you didn't have a full tank BEFORE your trip? Sometimes the gas pump nozzel will click making you think it's full when it's just air. Try it again, make sure your tank is full before you leave and make sure it's filled when you get back.

If you were doing quarter mile runs it's possible. ;-)

Tim B
 

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Chad, you got a stock carb too? If that automatic choke is not working, either fix it or wire it open to make sure its not closing on you. Another thing, check your oil. Yes I said check your oil, make sure its not over full. If it is check it to make sure it dosent smell like gas. A bad fuel pump can leak gas into the crankcase wasting gas and diluteing the oil. Not a good thing. mm
 

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My first Cat was back 25 years ago. It was a 72 standard, with the typical 351C-2V/FMX/3.00. That combo was good for almost 17mpg highway. I really didn't have much of an opportunity to check city mpg since this car's primary function was to get me back and forth to OSU from Cleveland.

My 302/AOD/3.08 Marquis used to get around 20.

When you start modifying things from stock, MPG generally goes down the tubes.

Alpha Cat used to eat me out of house and home. I took it on a road trip and got barely 11mpg. At that time, it was much modified 351C-4V/C-6/3.25. Beta, running a lesser modified 351C-4V/C-6/3.70 was getting closer to 15mpg highway.

Then again, my old Country Squire 460/C-6/3.00 got only 11mpg all the way from Phoenix to Cleveland, 2200 miles. Talk about gas guzzler! Wife's F-250HD 460/A4OD/4.10 gets 12mpg. Neither one of these vehicles care if they are going city, highway, or thrashing on 'em.
 

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Discussion Starter #11
Good tips mm. question: Should I I just take that choke plate thing off that carb? -because it is closed all the time... I still have to check the oil. I put some flowmasters on today. I don't know what that's going to do for my MPG, but I'll find out. More importantly it sounds good ;) I'm going to try and grab a 600 cfm edelbrock carb by christmas with an electric choke. I just picked up a 289 performer intake manifold the other day, so when I slap that on there I'll put the new carb on too. - I should be getting better milage with that. thanks for the tips ya'll - Chad
 

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Naw Chad, you dont have to remove the choke plate. Just wire the linkage on the side or loosen the choke thermostat ( the round black housing on the side) and rotate it till it holds the choke plate open all the time. That will at least hold it open till you get your new carb. By the way the 600 performer is a excelent choice for your 302, you will like it. Pretty much just bolt it on and forget it. I have one on my 351 and I got around 14-15 mpg on the trip to the James Dean run. My 351 is pretty much stock other than the very small cam, headers, offy dual plane, 600 and the 3.25 trac loc. It also is about wore out, using some oil too. So I really didnt the mileage was that bad. Your 302 should do at least that well.
 

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:1poke: hints: always check your odometer to make sure it is accurate 1st. check it against the mile markers on the interstate,then at 60mph it should take you exactly one minute to go one mile(sorry guys i know we all know this but hey it is important!) next fill up at the same place both times,using the same pump.parkingin the same spot.different gas stations may or not be level as the last one and pump shutoff can be different,put the nozzle in and remove it at first shutoff,dont try to top the tank,it's more important to be consisent than full of fuel.repeat step then figure fuel usage! your mileage dont sound too bad ,mine only gets 3/4 mile per gallon at $4.20 per gallon!!lol
 

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That is pretty bad mileage, but a closed choke is a good reason why. My 460 in my 70 is getting 18.6 @ 70 mph with an AOD and a 3.50 gear. It still runs a little rich on the cruise side. Gets about 12-13 around town. It can still be better.
I think with the 302, C-4 and 3.00, you should get about 17+ on the highway. Aroud town you should get abou 11-13. To accurately test highway mileage, top-off your tank, cruise a known distance, then top it off again.
Your ignition timing can make or break your mpg's. Make sure it is adjusted properly and if you want better part throttle economy, then make sure to run your vacuum advance on ported vacuum on the carb. I like to set the initial timing higher then stock--about as much initial as it will start with at operating temperature. Then to have the mechanical advance swing out to about 33-36 by no later then 3000 rpms--test that with the vacuum advance unplugged. With total mechanical timing and vacuum advance should be about 40-44 degrees all in no later then 3000 rpms. Make sure to run a thermostat----no less then 180. To really set up the ignition your self, the best tool to have is a dial-back timing light.
Good luck,
 

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Discussion Starter #15
ok i tinkered with the choke alittle and am now getting around 10 mpg. I still have some work to do on it. I put some flow master mufflers on it now and it sounds nice. thanks for the good advise everyone. - Chad
 
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