Getting horrible gas mileage?

[gslack]

I have an original 3 spd manual tranny
after market 550 cfm edelbrock carb
idles at 800 rpm
have 5/8 inch fuel line
302 v8.

anyhow I am getting like 7-10 mpg city and even less on the highway, a couple months back i was getting fifteen city and less on the hwy but im just wondering what is going on?

so does anyone have any suggestions on how to get better gas mileage, my driving habits are good I do not accelerate suddenly and i shift around 2000-2400 rpm.

help??

[akaFrankCastle]

If you were getting 15 out of a naturally aspirated motor in the city, I need to steal your set up.

Running a standard 2 barrel through a 3 speed and down to 4:11s and 33's I average 9.6 MPG (city/highway combined). I know Viper quoted me somewhere in the neighborhood of 15 on his EFI set up.

Bottom line is, I think you might have been miscalculating your numbers a few months back. Not saying your are wrong so much as if you are right about your numbers, I want to know your secret.

I went ahead and deleted that second identical thread.

[Viperwolf1]

You don't really have 5/8" (-10) fuel line do you? You probably mean 3/8".

I can see 10mpg city but a 50% change is drastic. Your odometer could be off and you might be basing your mileage on the wrong distance but as long as it's consistant the 50% reduction should be valid. If it doesn't run any different look for leaks. Check engine oil for signs of fuel leaking in from fuel pump. It can happen.

[gslack]

yeah i meant 3/8th lol sorry im pretty tired, i have that 550 cfm edelbrock 4 barrel carb, ive been considering throwing on the old two barrel i have, i have 31s, stock difs etc. i think the odometer might be a tad off as ive suspected but the range is pretty marginal cus if i take the car from mile marker to mile marker its pretty accurate.

im wondering if efi would help.
or would a 5/16th fuel line make a difference?

i just replaced pretty much my whole entire fuel system, new fuel filter, electrical fuel pump new sending units wiring gauges bla bla bla and there aren't any leaks i put all the hoses on pretty tight.

problem is i dont have much money and gas is killing me so i barely drive anywhere anymore except school even if i need something.

[gslack]

also i kind of suspect my transmission is about to go, around 2300-2500 rpm there is this weird noise that sounds like a slinky toy until im out of that range, and a couple times in the last few days when i started the car it made this weird sound that sounded like the starter cog was being bashed against the fly wheel.

i know its not the starter because i replaced that two thousand miles ago, but as far as i know my clutch and fly wheel are stock and there is 100,000 + on that tranny and the same on the motor. i have a long list of stuff i really need and want to do that car but i wont have the money til i get out of college.

[akaFrankCastle]

I get a slinky sound too, but mostly because the bolts in my transfer case shifter are a tad loose and the shifter vibrates when I'm driving.

EFI would help you with your gas mileage, but you are not going to be pulling 20s no matter what.

5/16s would be a step down in diameter from 3/8s and would only force that fuel pump to work slightly more to move the same amount of fuel. Have you rebuilt your carb? Going back to the 2 barrel would likely net you an increase in economy. But the numbers I quoted were with the 2 barrel on there. I just dropped a 4 barrel Edelbrock 600 on mine. No numbers to report yet as I am still working the Hydroboost.

If you do suspect the transmission is on its last legs, and considering it is around 100k it might be, I have two 3 speeds in the garage. You are welcome to one of them to rebuild while you keep driving your truck. Although, I don't know that a failing transmission would be the culprit here, unless it was somehow causing an undue drag on the entire power train.

[cobshane]

Efi isn't a cheap alternative either. There is a bit of money needed to the conversion

[gslack]

No I recognize that, my 550 cfm edelbrock carb has 10,000 miles on it and i bought it along with an edelbrock 289 preformer intake manifold when i bought the car in april of last year, i took the old manifold and 2 bbc off and im not really sure of the condition of that carb but i know it works. i think the transmission might be putting stress on the drive train because if i got around 2800 rpm i feel this weird drag on the car (the reason i did that is cus i feel some drag even around 2200-2400 rpm sometimes), like tensions is on the draft shaft and going through the axles to the wheels or something.

thanks btw i appreciate the offer on the transmission but once that bridge comes ill cross it, if the transmission does go out i think i will just get a tranny 4 spd tranny if possible so i can drive on the highway at lower rpms, most of my driving happens on the highway anyhow.