best way to improve fuel economy

[MadOgre]

Diesel.

Holy crap yes LOL my 6.2 got 22-25 mpg easily consistently with or with out pay loads

Of course that was with 3.42 gears and 35" tires @ 1:1 final gear with my TH400

 

[Stepperado]

Dont know what exhaust you have, but the biggest improvement I found was when I took out the stock catalytic converter and ran true duals from front to back. The best mileage I recorded (and I recorded a lot) prior to the exhaust change was 15.4 mpg. The very first tank I ran after the exhaust was installed was 17.2 mpg. That's 1.8 mpg improvement. I have a 305 instead of your 350, but that's a big improvement, plus it sounds cool.

 

[MadOgre]

You know a nice fresh little 305 with 4:10 gearing and an OD would work fairly well and be good on fuel!

I had a new 305 once that a GM tech rebuilt I put an Edelbrock Performer 2101 and a nice Quadjet on it, and it went way better with that 2101 vey noticeable improvement over the factory intake. I would guess I got about 25 hp and the low torque really kicked in. I actually miss that little 305

 

[MikeB]

5-7 mpg on a good day, and 3 on a bad day. Heck, a NASCAR engine probably gets at least 3 mpg at 9000 RPM.

Something definitely isn't right with your engine. What model# is the carb (1405, 1406, 1407, 1411, etc), and has anyone messed with the jetting?

Does it start and run OK?
Does it smoke?
What color are the plug electrodes?
Have you checked the ignition timing -- initial, centrifugal, and vacuum?
If you have a tach, at what RPMs does the engine spend most of its time?
How many revs does it turn at 60 mph?

I wouldn't just run out and buy a new carb expecting things to get better, unless your Edelbrock is a 750 or 800 with extremely rich jetting.

I've had several Chevy pickups with small block/TH350 combo over the years, even a 383, and the worst I ever saw on the highway was ~10 mpg, and that was with a 307 2 bbl (!) I improved that to ~13 mpg by going to a small 4 bbl and dual exhausts.

 

[MadOgre]

If he bought a new Quadjet it probably would solve his issues what else is gonna cause that unless hes running on 4 cylinders

 

[MikeB]

So, nothing but a new Q-jet -- and manifold and linkage and fuel line, etc -- and that $500-$600 investment is gonna give him how much more gas mileage?

We don't even know which carb he has yet! What if it's an Edelbrock Q-jet?

And what if the problem lies somewhere else?

Another question for the OP: How much engine vacuum do you have at idle in Park?

 

[MadOgre]

I was just making the point that it most likely does revolve around the carb I would over haul it myself but if that's above someone's comfort level then a new carb would produce similar results. But yes you are right its very premature at this point to just go buy a new carb.

 

[MadOgre]

Oh it is an Eddy lol probably jetted way wrong

 

[350runner]

if it's an eddy q jet. trash it lol. finding aq jet in the salvage yard $50 max, rebuild kit $20, intake caigslist? $100. $500-$600 hmmmm



Sent from the dust in front of you!

 

[MikeB]

if it's an eddy q jet. trash it lol. finding aq jet in the salvage yard $50 max, rebuild kit $20, intake caigslist? $100. $500-$600 hmmmm

Sent from the dust in front of you!

Been there, done that with junk yard and craigslist stuff. Good luck with that.

And if gas mileage doesn't improve? What ever happened to troubleshooting BEFORE buying parts???

I'm more of a Holley guy, but used to buy, repair, and sell Edelbrock 1405/1406/1407/1411 carbs. They work just fine with stock to mild cams, and are NOT the problem here due to some kind of design flaw, which some of you imply. Now if his carb is set up wrong or needs a good cleaning (clogged air bleeds, etc.) then that's another story. But it's still no reason to trash it!

 

[350runner]

It's been agreed across many boards that q jet is better for performance and mpg in stock form and modified. good luck with getting a Holley to hold a tune... just saying.

Sent from the dust in front of you!

 

[MadOgre]

Yes 3MPG is gawdawfull even for an Edelbrock. Ceasar is right. The Quadjet will offer better MPGs and even perform better than an Edelbrock. Hands down! Reason being the small primaries and the vacuum secondaries. And although its the most difficult to rebuild it actually operates very simply. The only reason guys swap in an Edelbrock is because they get sick of trying to fix their leaking fuel well plugs.

But Im sure the OP is wanting to know what's wrong with his current setup instead of listening to us argue about what carb is superior. lol. Although I haven't heard the OP in a while on here so I dunno ???

Im guessing it is jetted way to rich. A lot of times guys get a carb from their buddy who had it on his race motor. So it will make my motor go fast Too!!! Right?. Wrong because its jetted way to rich. And the 750 CFM Edelbrock is way to big for a 350 Cubic inch small block. 600-650 cfm is all that is required for a 350 even a built 350. So im guessing the problem is its a 750 jetted rich ???

 

[Joe383]

Do a 700R4 swap. I paid $150 for my last 700R4. It did not have the converter and needs a lock up kit but its worth it.

 

[seniorbear69]

Hi all i have a 84 c20 with a recon th400 a 305 with a mild roller cam a quck fuel 600 slayer duel exhasts and im geting 8 im almost sure have 4.10 in the rear im looking for a way to get this in double figures sumhow ! love the old girl but not to fond of 8 mpg !

 

[Turbo4whl]

Hi all i have a 84 c20 with a recon th400 a 305 with a mild roller cam a quck fuel 600 slayer duel exhasts and im geting 8 im almost sure have 4.10 in the rear im looking for a way to get this in double figures sumhow ! love the old girl but not to fond of 8 mpg !

Read my tongue in cheek post #35

https://www.gmsquarebody.com/threads/what-am-i-looking-at.33205/page-3#post-669426