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Old 03-22-2004, 08:08 PM
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GAS Mileage

I have a 78 camaro Z28 350 stock engine with headers and flowmasters. 3.42 rear gear with a th350 trans. I get right now about 9 miles a gallon city and i was wondering how to get better mileage. I also want more power. know my dad says that you cant make more power with out hurting your mileage is this true. If not what can i do that will help my mileage. I know they are gas eating machines but it cant hurt to try and get a little better mileage.

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Old 03-22-2004, 08:22 PM
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Lets see a 17 year old kid in a Camaro with a v8 I think 9 miles to the gallon around town is probably pretty good.

You could put a new 195 degree thermostat in it.

Check adjustment of idle mixture screws.

Check the choke adjustment.

Check your timing.

Check that the mechanical & vacuum advance are working and hooked up correctly.

New spark plugs.

Change oil.

Check air pressure in tires.
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Old 03-22-2004, 10:32 PM
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Hello Greg,

I think you forgot to mention that he could also put on a really big throttle return spring...

Tom
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Old 03-22-2004, 11:09 PM
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A little recurving of the distributor might help & it wouldn't cost a lot.
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Old 03-22-2004, 11:21 PM
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there`s a few things you can do to add performance without hurting mileage that won`t break the bank. add a K&N air filter, do a complete tune up with the best pieces you can afford, use spiral core spark plug wires and not cheapy part store solid core wires, take your time and route the wires correctly, next add a low restriction muffler such as a flowmaster or the like, pick up a advance curve kit for your HEI and recurve it for better spark advance, drain the rear fluid and replace it with royal purple gear lube, this will cut rolling resistance, and your unit is likely a limited slip unit being it`s a Z28, but with the royal purple lube you won`t need to add the GM limited slip additive, check the front wheel bearings, clean them and repack them with synthetic grease. lastly, if the engine has over 40,000 miles on it, I would add a new timing chain. after these mods, I would set the spark timing at around 10 degree`s before top dead center, these mods will give you more power as well as better mileage.
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Old 03-23-2004, 08:42 AM
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mileage??? your problem is not a tuneup bit an attitude change, its not the mileage but the smileage that counts

(smileage is calculated as the amount of smiles per gallon of premium gas)
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Old 03-23-2004, 11:13 AM
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Sorry to burst your bubble but with a 78 350, 3 speed auto. you are not going to get good mileage. No matter what you do to that combo it's going to average 13MPG. 9 around town sounds about right.

I have a 78 350 Camaro with 3.15 gears and short 14 inch wheels/tires which puts it in the 3:55 ish range like your 3:42 set up with 15 inch wheels.

The biggest thing you could do to improve overall fuel economy is to install a set of 2:41 gears. Once I Swapped out my 2:41 gears from a 305 Camaro with a 350 Camaro that had 3:15's and the 350 picked up about 1-1/2 to 2 MPG. My 305 lost about 1MPG with the 3:15's installed. Car will be a little sluggish with 2:41's but will have an amazing mid-range on the freeway, 2nd gear is good for like 110MPH!

No matter what I've done to that car it gets 13 MPG. If you jet it lean and back off the timing a little it's a total dog and still gets 13ish, maybe 14, but it's not worth adding close to one second to your ET .

Enjoy it for what it is and if you want mileage you should think about some late model muscle. EFI with overdrive is the only way you are going to get decent mileage and performance and still make some power.

My 78 sits in the garage now and my daily driver is an 89 5.0 5speed Mustang. It averages 24-1/2 MPG and is about as quick as my thirsty 350 that uses nearly twice as much fuel.

Last edited by Goldduster360; 03-23-2004 at 11:23 AM.
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Old 03-23-2004, 11:22 AM
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One reason your mileage could be so poor could be, if your letting the car warm up for a good while, and then driving a few miles to school, then letting it warm up and driving it home a few miles. That goes for any other time you go to drive it, lots of idle time and short driving distances, combined with Philadelphia traffic is going to really hurt mpg.
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Old 03-23-2004, 12:09 PM
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Hmm, well if you're really worried about it, edelbrock boasts that some of their setups will get 20mpg! Call them up I remember one guy in their magazine had a crate motor in his ride and cruised getting 20 with it. You might be able to just get a cam and intake from them, probably a carb too, and that would probably help. Headers make your ride more efficient as well as roller cam and roller rockers. The biggest and best change you could probably make would be better, more efficient heads.

K
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Old 03-23-2004, 12:15 PM
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In addition to a higher flowing air filter and exhaust setup, I hear that an aftermarket multiple spark ignition will increase both mileage and horsepower. You could also unhook the secondaries. I know when I was your age, my dad did that as a "safety measure"
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Old 03-23-2004, 01:10 PM
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My sister got a Nova for her first car. We put a bolt through the gas pedal so it would only travel about half way to the floor. You might want to try that, I guarantee you will get better mileage!!



Just kidding!!!



The advice given so far is sound, tune it up and lay off the secondaries once in a while and you will do a little better.

Remember, you are driving a v-8 car made out of steel. Not some 4 banger plastic hunk of junk.
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Old 03-24-2004, 03:06 AM
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i think the best way to up the mileage is to install a 700R4 transmission, in overdrive and lockup, yuoll get the advantage of the lower gearing suggested above and with the converter locked up there is no horsepower robbing slippage..

www.700r4.com
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