Need better gas mileage...

[65fastbackresto]

6 mpg is what I`m getting now, there has got to be something I can do to help this. Its just a built 302, small lopey cam, and 10 to 1 comp. I`m having to run premium cause of the compresion, but what can I do to help the gas mileage? I have Edelbrock 600 with electric choke and its just like it came out of the box with only the idle and fuel-air mix screws messed with.

Smaller carb maybe?

 

[jlangholzj]

ha!

what exactly are you rear gears? 3-spd, 4 or a T-5 ?

I have a 289, 600 CFM holley, a mild crane cam, C-4 and 3.00 rear gears and on a GOOD day, i can get in the 12 range (of course, who's to say this isn't b/c of my driving style )


I'm geussing that if you have say 4.11's, your doing pretty darn good with 6 mpg, but if they're 3.00, you might just need to tune things up.

at an arm, leg and a left nut, running 6mpg on $4.15 gas is definately not fun! (well actually it is!!! but your wallet won't like it) but hey, its better than avgas ($5.50 per !! )

 

[D.Hearne]

Refresh our memory's----What rear gears and stall are you running ?

 

[70vert]

With an OEM '70 302-2v, 2.73 rear, and a .64 final drive TKO600 5-speed, I have gotten (no joke) close to 25mpg on a 150 mile mixed freeway/country road drive. I have pretty meaty 245/275 tires too. It can get better! Do you have a manual or auto?

 

[suki243]

25?! thats some good stuff.

 

[Fast63]

what kind of fuel pump do you have? edelbrocks can't run over 6psi of fuel pressure because it will open the needle and seats and dump gas in your engine. Also, what is your timing at? Does it advance?

 

[Hack]

Tune up and keep your foot out of it. Don't expect 25 though! Methinks someone's speedo is a little off, that's pretty unusual. The biggest thing you can do is to drive really easy, like you have a crappy little 4 cylinder in there. Stay at or under the speed limit on the interstate.

 

[jlangholzj]

what kind of fuel pump do you have? edelbrocks can't run over 6psi of fuel pressure because it will open the needle and seats and dump gas in your engine. Also, what is your timing at? Does it advance?

does this go for holley's also? just curious.

 

[70vert]

That's why I didn't use the speedo! I Google Mapped the drive, filled up at the beginning, and filled up at the end. Seriously, with a 2.73 rear and a .64 final drive OD, driving 55 on the freeway feels like idling. And the untouched 2v had something to do with it, I'm sure. 91 Premium gas.

 

[65fastbackresto]

I`ve got a c-4 tranny

and 355 posi track, and the speedometer says about 90 mph when I`m running 55, but I can fill the tank up and drive about 50 miles, and the gauge is under 1/4 tank.

As far as tune up, it aint had enough hours to be tuned in yet, much less wear and tear on stuff.

 

[rbohm]

and 355 posi track, and the speedometer says about 90 mph when I`m running 55, but I can fill the tank up and drive about 50 miles, and the gauge is under 1/4 tank.

As far as tune up, it aint had enough hours to be tuned in yet, much less wear and tear on stuff.

ok first we need to get your speedometer and odometer right, they are WWWAAAAAYYYYYYY to far off. depending on what tire you are using you need a 21 tooth driven gear. and that is likely part of your problem.

as for what you can do for tuning, start by swapping to a smaller jet and metering rod combination. i used a 93 jet with the corresponding metering rod in my grand marquis to reduce fuel flow.

 

[chromedog]

6 mpg, thats pathetic... my 351, comp cam, 600 holley, aod with 3:00 gear got around 18 before i swapped to the 3:50 gear. now its around 15 if i keep my foot out of it. i would do a plug check, and try to jet the carb down... WAY down!

 

[65fastbackresto]

This bites....

I dont know how to change jets and metering rods, I got a buddy that can though I hope.

 

[SadbutTrue]

I dont know how to change jets and metering rods, I got a buddy that can though I hope.

it aint' hard, just read the manual on it. Jet changing takes about 10 minutes, even for the mechanically un-inclined. Don't even need to get your hands dirty.

when you say 'mild cam' do you have any idea what specs are actually on it?

If someone sold it to you saying it was just a lopey/RV cam but its actually some radical monster stuck in the body of an otherwise stock or near stock engine (trust me.. it happens... some people are really strange when it comes to cams), then that might explain why your mileage is terrible.

Other than that, cant do much except look for vacuum leaks, tune it up as far as timing and A/F ratio goes, and new plugs.

 

[65fastbackresto]

Well....its pretty freaking scary when I flog it

Not exactly sure of the cam specs, but the lift was just under 500, and the duration was I think 236, with LSA of 108.

Even in a straight line this thing will pin ya to the seat and wiggle when changing gears, I never thought a small block ford could do this, I`ve had a couple of good chevy 350 motors, but nothing I ever had ran this good. (light car too though)

The fuel pump is stock.

I think the carb came with a dvd, I`ll look into that.

 

[SadbutTrue]

Not exactly sure of the cam specs, but the lift was just under 500, and the duration was I think 236, with LSA of 108.

Even in a straight line this thing will pin ya to the seat and wiggle when changing gears, I never thought a small block ford could do this, I`ve had a couple of good chevy 350 motors, but nothing I ever had ran this good. (light car too though)

The fuel pump is stock.

I think the carb came with a dvd, I`ll look into that.

yeah, its probably just something small. that cam doesn't seem too ridiculous, though it is a bit big for an otherwise near stock motor. give it a good tune with new plugs and mileage should come up some.

 

[jlangholzj]

Not exactly sure of the cam specs, but the lift was just under 500, and the duration was I think 236, with LSA of 108.

Even in a straight line this thing will pin ya to the seat and wiggle when changing gears, I never thought a small block ford could do this, I`ve had a couple of good chevy 350 motors, but nothing I ever had ran this good. (light car too though)

The fuel pump is stock.

I think the carb came with a dvd, I`ll look into that.

HA! I hear ya! it's kinda scarry how much some of the SB's can actually put out.

 

[gonzothegreat]

342, with a lumpy 280 roller cam.
10Mpg in town
19Mpg combine (80% motorway, 20% town)

3.55 gears and T5 gearbox.

 

[D.Hearne]

and 355 posi track, and the speedometer says about 90 mph when I`m running 55, but I can fill the tank up and drive about 50 miles, and the gauge is under 1/4 tank.

As far as tune up, it aint had enough hours to be tuned in yet, much less wear and tear on stuff.

Speedo gear tooth count also needs to take in account the tire size (diameter) I'm running an 18 tooth in my 77 Comet with 3.50's and 26.5" tires and it's dead on the money, untill you hit about 80, then it goes haywire. You can't really go by the reading on the fuel gauge to figure mileage, you have to get the actual miles and divide by the gallons used. The C-4 doesn't help things either, especially if it's got a radical stall converter.

 

[Fast63]

does this go for holley's also? just curious.

It depends on which model holley I believe. Some can handle up to 7 psi, while others can handle 9+psi. I know the stock holley on my 85 stang runs with the stock fuel pump, which puts out 8.5 psi. I have heard people say a basic 4160 holley shouldn't run more than 7psi though. I have less experience with holleys because I just don't like them at all, so someone else could give you a more precise answer on a specific model, or you could always call holley's tech line.