Going to replace Edlebrock 650 with 500, what can I expect?

[ubtripn]

The PO put a new 650 on this 350. I added a 700R4 and still haven't id'd my rear end yet. I am thinking about putting the Edlebrock 500 on my engine. It says it's the gas economical version. What do you estimate it will do to my MPG? Will the power be a great deal less? The engine feels over-carbed with the 650.

[69GWC]

Is the motor stock.?
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[ubtripn]

It's unknown but I would guess yes but now I am reading that the 600 is calibrated for better gas mileage.

[ubtripn]

Maybe I am better off going with a rebuilt quadra-jet.

[jocko]

that'd get my vote... (qjet). I used to not be a fan, tried Holleys, Carters, Edelbrocks. Found that for stock apps I prefer the Q.

[ubtripn]

Which is the best model of quadra-jet for mileage on a 350 "in general"?

[69GWC]

Jetting and the tuning of the carb has alot to do with it, if the 650 you have is not jeted well for your motor its not going to get good mileage as neither would any for that matter.
But the smaller carb might come out of the box jetted better than the larger one and that only would help in both power and mileage.

Q-jet is a good carb but still needs tuned for your motor to get good mileage and power.
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[ubtripn]

Ok, thanks. I will have to do much, much more research.

[jocko]

one note on the Q-jet and mpg - a LOT has to do with driving habits. once properly tuned, you can get decent mileage by calm driving habits using the teeny primaries or you can get HORRIBLE mileage by trompin on the secondaries. This is true in any carb of course, but exaggerated at each end of the spectrum for a Q-jet because of the small pri/large sec combo. Same as a spread-bore Holley.

[ubtripn]

I hear you. I drive pretty easy. I don't like wasting fuel.

[68Stepbed]

The 500 is better tailored for a 350 than any other carb(besides a properly tuned Q-jet). I once had one on a stock 350 and it ran great. It's the only Edelbrock I ever had that ran good. You will get better throttle response, which means you won't have to give it as much throttle to pick up speed which will increase fuel mileage.

When it comes to carbs, bigger is not always better.

[truckster]

Summit has remanufactured Quadrajets for about $300. I would call them and talk about your specific application, and they can make sure you get one that's jetted and set up right out of the box.

[Longhorn 70]

Edelbrocks are SO much easier to work on than QJets. If you do your own work this may be something to consider.
1.You also do not have leaks in Edelbrock like the QJets.
2. Edelbrock has no gaskets below float level.
3. Floats are adjustable without taking the carb off the vehicle.
4. Needle and jet changes much easier for easier tuning.
5. Hold off springs also easily changed.
6. Pump stroke changes in 10 seconds.
7. More flexibility in tuning.

I think the 500 is enough or 650 if you are in high altitude.

BUT ALL THAT SAID. QJets were the original equipment. Still Edelbrock gets my vote.

My Big Block Olds, mildly cammed and HIGH compression with an Edelbrock 750 on it gets 15 M.P.G. if I drive mild.

[GASoline71]

One thing to mention. If this carb is going on a high mileage engine of unknown age or build... then you are likely to not see any improvement at all.

having a tuned and well runnin' engine in the first place will make all the difference in the world.

My 420+ hp 355 will get 12-14 mpg if I keep my foot out of it. It was built 6 years ago, and has a 750cfm Holley on it. So carb size really matters not. My engine is built for the upper RPM's to make power as well.

Gary

[Roger71SWB]

I put a Edelbrock Air Gap manifold and 600CFM on my 350 and love it. Just my two cents

[ubtripn]

I don't know then. I have tuned this carb pretty well but I know I am pulling single digit mpg and with a 700R4. I have to get a better rearend and crate engine with an injection kit to be happy I think.