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350 5.7 fuel mileage #733946
March 12th 2018 4:47 pm
March 12th 2018 4:47 pm
Joined: Feb 2018
Posts: 56
Ohio
J
jgarrett Offline OP
journeyman
jgarrett  Offline OP
journeyman
J
Joined: Feb 2018
Posts: 56
Ohio
i have a 350 with a stock quad jet carb on it. I think im only getting around 10mpg. Would i be able to get any better gas mileage with a new quad carb?

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Re: 350 5.7 fuel mileage [Re: jgarrett] #733947
March 12th 2018 4:57 pm
March 12th 2018 4:57 pm
Joined: Nov 2013
Posts: 2,670
Michigan
Dyno_Dave Offline
veteran
Dyno_Dave  Offline
veteran
Joined: Nov 2013
Posts: 2,670
Michigan
If the current carb is the problem, perhaps. And I DO NOT mean that to sound like a smart ass answer. A properly tuned Rochester Quadrajet can deliver good mileage. The small primaries for cruising make it an efficient carb under light throttle / load.

But there are LOTS of variables for fuel mileage. State of tune (plugs, wires, PCV, no vac. leaks), weight of vehicle, aero (extra wind dragging spoilers or raised roof?), driving style (do yo udrive conservatively, or a little more aggressively?), driving conditions (cold weather with lots of choke operation, lots of hills?), gear ratio, OD trans? Is the choke opening as fast as it should (or is the heated crossover that powers the choke clogged...or is it electric and inop)? Timing (set to spec, or retarded to allow low grade fuel, further retarded to avoid spark knock from carboned up combustion chambers from leaking stem seals, or inop. EGR)? Vacuum advance working? Lots of things go into it.

But a worn out carb, with floats that are 1/2 sunk leaving it running rich? Sure, that will hurt MPG, and a rebuild would fix that.


Re: 350 5.7 fuel mileage [Re: Dyno_Dave] #733949
March 12th 2018 6:33 pm
March 12th 2018 6:33 pm
Joined: Feb 2018
Posts: 56
Ohio
J
jgarrett Offline OP
journeyman
jgarrett  Offline OP
journeyman
J
Joined: Feb 2018
Posts: 56
Ohio
awesome man definitely alot to think about. I think ill start with replacing some of the vacuum lines and changing the egr valve right away.

Re: 350 5.7 fuel mileage [Re: jgarrett] #733950
March 12th 2018 7:46 pm
March 12th 2018 7:46 pm
Joined: Mar 2016
Posts: 322
Tucson,Az.
H
Hasan Ben Sobar Offline
enthusiast
Hasan Ben Sobar  Offline
enthusiast
H
Joined: Mar 2016
Posts: 322
Tucson,Az.
What Dave said. You timing curve is in need of attention as well. Talk to someone who knows how to tune a SBC. The Q-jet is NOT the weak link in the chain if all other things are equal..


Tucson-it's a dry heat...like an oven

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