Gas hog

[SamHam]

My gas mileage has noticeably gone down recently. I have checked my whole fuel system for leaks and havent found any. In the last 13 days I have spent $120 on gas and I hardly drive. I'm not sure if this could be correlated with my fuel economy but when coming to a stop or making a turn my rpms drop almost to the point that my engine dies. I am usually pretty quick to figure out these kind of problems but I am at a loss for this one. Hope one of you guys might know the answer, thank you.

 

[TotalyHucked]

Sounds your carb could use some attention. What's your whole setup and what were you getting for mileage before/after?

 

[JD Miller]

Put a cummins diesel in it....

 

[SamHam]

Sounds your carb could use some attention. What's your whole setup and what were you getting for mileage before/after?

I have a 615cfm Edelbroken carb that's only a few months old, its on a 1st gen 4 bolt main 350 paired with an sm465 transmission. I have 31" tires and no lift. I'm not sure what mileage I was getting before but i know my gas gauge wasn't going down as fast as it has been recently. I'll adjust my carb right now and post an update in a few hours.

 

[TotalyHucked]

Or it could be the gauge failing. Without knowing your actual mileage, it's impossible to know if you have an actual issue or not

 

[Ricko1966]

Make sure your vacuum advance can hasn't ruptured,and is connected to manifold vacuum.

 

[Memaloose]

Maybe someone siphoned some fuel out. You never know.

 

[Bextreme04]

I have a 615cfm Edelbroken carb that's only a few months old, its on a 1st gen 4 bolt main 350 paired with an sm465 transmission. I have 31" tires and no lift. I'm not sure what mileage I was getting before but i know my gas gauge wasn't going down as fast as it has been recently. I'll adjust my carb right now and post an update in a few hours.

Weather got cold up here recently and they probably switched to winter blend now, which will show a few MPG lower. Your stumbling at idle makes me think vacuum leak though. Start it up and spray some carb cleaner all around the intake manifold and see if you notice an RPM change. What part of Oregon are you in?

 

[bucket]

My gas mileage has noticeably gone down recently. I have checked my whole fuel system for leaks and havent found any. In the last 13 days I have spent $120 on gas and I hardly drive. I'm not sure if this could be correlated with my fuel economy but when coming to a stop or making a turn my rpms drop almost to the point that my engine dies. I am usually pretty quick to figure out these kind of problems but I am at a loss for this one. Hope one of you guys might know the answer, thank you.

Have you actually calculated your mileage? If so, what is it now, compared to before? What type of driving do you do? Have you been letting it warm up before you drive it?

 

[77Dmax]

Does it stink like fuel? Is it running ok besides the idle issue?

 

[SamHam]

I live in western Oregon so its about 40-50 most days right now. I haven't calculated the actual mileage yet but I will next time I fill up, which is probably soon lol. I will try the starter fluid trick and check all my vacuum lines. I'm suspecting its just bad carb tuning right now.

 

[Scott91370]

Didn't read all the replies but your area could be starting the use of winter fuel which will hurt MPGs.

 

[Grit dog]

Winter blend gas usually is only a couple % less efficient. Hardly noticeable. Certainly not grossly worse.
However $120 in 13 days “ not driving much” doesn’t even begin to calculate to fuel mileage and even if it did, no basis for comparison.
Idk if the wet side of the Cascades runs winter gas or not.

All the suggestions above are good places to start.
And it may just be the Eddy carb. I have 2 now one in a big block other on a 350. Haven’t spent the time to try to tune them, but a 750 Eddy on a Gen VI 454 pushing the worlds heaviest 35s with 4.10s = 6-7mpg. And an assuming smaller carb idk what model or cfm on a poochy new 350 1/2 ton with 3.54s is about 11-12mpg.
For reference.
The big one may be running a bit rich, not horribly though. The little one burns clean at the tailpipes.