Need better mileage

[BigPoser]

So I finally got my first tank emptied today and filled it up. Figured out that I got a whopping 8.6 MPG. That sucks $hit. I have a 350 that has a Edelbrock performer intake. Been told that heads play the biggest part of mileage.

Any recommendations for some heads that will help me with improving my mileage? Any tips in general for improvement.

Thanks in advance.

Brandon

 

[CSFJ]

What's the rest of the equation? Is the carb original or aftermarket? which trans do you have, and rear end gear ratio? What size tires are you running, and what kind of driving do you do? (highway, side road, combo of both?)

 

[PrairieDrifter]

If you can get the rpms down youll get better mileage so, gear ratio, tires all that will help you.
Have you done a tune up recently? Plugs, wires, cap, rotor, filters, and fluids?

 

[BigPoser]

What's the rest of the equation? Is the carb original or aftermarket? which trans do you have, and rear end gear ratio? What size tires are you running, and what kind of driving do you do? (highway, side road, combo of both?)

Forgive my ignorance on this matter and thank you for the help. I'm still learning a lot about motors and such. To answer your questions: Carb is an Edelbrock 1405. Tranny is a 700r4 and not sure of the gearing, but it is not set up for performance. Tires are stock 15's so 235/75/15 I think. Driving is purely commuting and around town as this is my daily driver.

It has HEI ignition and I haven't done anything with it yet and is stock. Wires are Autolite 8.5mm and were on the truck when I got it. I have plugs on my shelf and are going in on Thursday. New fluids throughout.

Trying to maximize my MPG without spending a ton, but willing to spend some if needed.

Thanks again.

Brandon

 

[bucket]

That's not TOO awful for around town driving, but no matter what the gear ratio, I think you should be getting at least 2 mpg better than that. Eddy carbs are known to run fat at low RPMs. Have you pulled any spark plugs to see what they look like?

 

[CSFJ]

That's not TOO awful for around town driving, but no matter what the gear ratio, I think you should be getting at least 2 mpg better than that. Eddy carbs are known to run fat at low RPMs. Have you pulled any spark plugs to see what they look like?

I've heard the same about the Edlebrocks too. Everything you posted runs down the same tracks my train of thought was going.

 

[rich weyand]

The 1405 is "calibrated for performance", which means it is even richer than most Edelbrocks. So your carb tune is all wrong for that engine. And it's showing. I get 10 mpg in town with a K10 with a TH350 and 31" tires on 3.73:1 axles.

Edelbrock 1405 is .100 primary, .095 secondary, 70/47 rods, and 5" step-up springs. What you need for that engine is more like .092 primary, .095 secondary, 65/57 rods, and 8" step-up springs. These are easy changes. Here's the part numbers you need: primaries: jets .092 (#1425), rods .065 x .057 (#1461); secondaries: stock; step-up springs: 8# (comes with #1464). You will also need to replace the airhorn gasket (qty 5 is #1499) when you change the primary jets. Adjust the float bowls while you are in there, as they will be wrong, probably to the high side.

Then, you need to adjust your timing. Odds are you have the vacuum advance in the wrong vacuum port, are running the wrong vacuum advance can, and have the timing way retarded from its optimum setting. This will all cost you in fuel consumption.

Read this on timing: http://www.gmsquarebody.com/forum/showthread.php?t=14508

And put the AR23/VC1853 vacuum advance canister on the distributor.
http://www.napaonline.com/Catalog/C...cuum-Advance-Control/_/R-ECHVC1853_0168354142

 

[bucket]

Yeah, forgot to mention the timing. If it's set back too far, it can really make the mpg suffer.

 

[rich weyand]

One additional note. Vacuum advance canisters are stamped with their part numbers. This stamping is on the "tang" of the canister that goes into the distributor, and can usually be seen by looking straight down between the can itself and the distributor cap.

What is the stamp on your vac advance can?