Gas mileage

[kyle7713 10]

Post your gas mileage and your setup or how you have it tuned.

 

After a few months of hardcore research and constant tuning i have managed to get 23 mpg highway out of a 351w with an FMX trans.

[fortuna 10]

What did you change on your car to get that mileage?

[chillininnh 21]

418W (RPM Air Gap, Dart Pro1 195, Comp XE294H (31-254-4)

TKO600

3.70 Auburn

Holley Street HP 750 double pumper (stock jetting, going to Dyno tune this spring)

MSD 6AL2

24 initial

10 mechanical advance

34 total

2 light blue springs

20 gal tank

200 miles

10 MPG

I could care less about the gas mileage.

[FrozenMonkey 12]

I'm lucky to get 10 mpg out of mine. 8 is about where it stays. I like to get into it though so I'm not helping myself.

[MustangChuck 16]

Back when it ran....

302, bored out .040

Stock 68 302 heads

Clevite pistons

Unknown "performance" cam (previous owner didn't give specifics) -- probably not much over stock

Timing tuned by ear, unknown actual numbers.

Carter AFB 625 carb

Cobra (same as Edelbrock F4B) dual plane intake manifold

4 speed top loader with 3.20 traction lock rear gears

 

At 70mph on the interstate, I would get about 14-15 mpg (~3000 rpm). In town was much lower.

 

Chuck

[Project69 10]

After a few months of hardcore research and constant tuning i have managed to get 23 mpg highway out of a 351w with an FMX trans.

 

I'm building my car with the same engine and trans and would love to know what you did to get that. 2 thumbs up. :tt1:

[FoMoCo1969 10]

i can get 28-29 on hiway with no a/c. but mines stock 88 5.0 HO, speed density, fuel inj. with an AOD and 2.73 gears. these motors run lean. (only thing ive added was longtube headers)

[Phils69 27]

408W stroker AFR205's : 10 light poles per gal

[Max Power 74]

23mpg through an FMX is a trick and a half.

[PxDnNinja 10]

Last time I drove mine, it was cross country (Utah - Kentucky - Utah) and it averaged around 15-18 MPG. I was a bit surprised by that.

 

Though it did break down 200 miles from home on the return trip.... :(

[jkskinsfan 19]

351W, 2bbl, FMX, 2.75 : 1 Rear axle. Completely Stock. In the nearly 4 years since I've had tags on it, I've driven it 3,377 miles, used 242.66 gallons of gas. The lowest MPG per tank was 11.51, and the highest was 16.80. The total average is 13.92 MPG.

[danno 128]

I have a 302 and have tried for years to get better mpg. I installed 351 Windsor heads, headers, even a AOD tranny. The engine was rebuilt recently and has good compression and everything is about as good as it can get. I still only get abotu 14mpg, and really wonder what those who claim 20+ are smoking?

[69gmachine 15]

Although it was not typical, the best I ever got when I had a 351W with twisted wedge heads, a mild crane cam, 600 cfm Autolite 4100, 1 5/8 headers and a T5 was 23 mpg. That was on a basically straight and level highway (I-95 to I-20) while driving from Washington DC to Dallas TX going 60 to 65 mph. Around town I got 13 to 14 mpg.

 

The best I've done with my 408 is a tad over 19. That has been very repeatable as long as it's all highway miles and I stay around 65 mph. Around town that drops to around 11. If I speed up to over 70 (which is typical) it will drop to 17 or 18, depending on how much over 70 I'm going.

 

Contrary to what danno thinks, I was not smoking crack. I think his car runs rich.

[kyle7713 10]

I'm building my car with the same engine and trans and would love to know what you did to get that. 2 thumbs up. :tt1:

 

Sorry for not answering i was slammed with finals. I have a HEI distributor that took a long time to set up just right with custom ground weights, 195 thermostat, edolbrock 1406 carb yjats been internally polished/deburred and tuned by the plugs/feel in 1000 rpm increments, performer intake, fmx has shift kit hooked up to a very tight tq converter.

 

lots of trial and error on this on, since in my daily driver i have had plenty of time to play with it lol still chirps the tires shifting into 2nd

[danno 128]

Sorry for not answering i was slammed with finals. I have a HEI distributor that took a long time to set up just right with custom ground weights, 195 thermostat, edolbrock 1406 carb yjats been internally polished/deburred and tuned by the plugs/feel in 1000 rpm increments, performer intake, fmx has shift kit hooked up to a very tight tq converter.

 

lots of trial and error on this on, since in my daily driver i have had plenty of time to play with it lol still chirps the tires shifting into 2nd

 

 

I have always wondered about the timing with my 302. You said you had custom grond weights, what were they adjusted for? A certain advance at a certain speed?

[69_Mustang 26]

Somehow, when i first bought the car I was getting around 20mpg on the HWY (in SoCal OC/SD area during NO traffic)... I was definitely blown away. Rebuilt engine as of last year (said the previous owner) and basically all stock, other than the fact it had a performer RPM intake mani and also has a 600 CFM Holley (4bbl). She might of been lean, because soon after I got her all tuned up and she was maybe getting 17mpg on the HWY.

 

After the doug tri-y headers, dual 2.5" exhaust with x-pipe, electric fuel pump, MSD 6AL, timed, tuned up a bit (or whatever it's called lol) and now shes gets 12-15 MPG, if i'm lucky on the HWY. Something like 7-8 MPG on the street.

 

I haven't driven her yet, but already on there and waiting to get adjusted is a 750 CFM Edlebrock (4bbl). I wanted to do heads/cams and supporting parts, but I bought front coilovers instead and going to get some wider tires (255 front/295 back). I'm sure at that point I'll get something like 10 MPG HWY... haha.

 

I hope when I open her airway up some more with the heads, cams, pistons, etc, I'd expect MPG to go up a bit, as long as I'm just crusing. That's what has happened with my last 3 vehicles, but they weren't carb'd either. lol

Edited May 15, 2013 by 69_Mustang

[RPM 1,190]

Hey 69Mustang, I believe everything but no traffic in SoCal :)

 

Bob

[kyle7713 10]

I have always wondered about the timing with my 302. You said you had custom grond weights, what were they adjusted for? A certain advance at a certain speed?

 

yes i ground the center section of the weights to allow for more or less total timing (every engine reacts a little differently) and have timing come it smoothly till maxing out at 2800 rpm, i offset my high initial timing and total timing set up with the greatest vacuum advance sweep i could get to prevent knocking while giving great cruising efficiency. ooo the many many long night i spent researching combustion and thermodynamic theories to figure this stuff out

[PaleRider 12]

347 Twisted Wedge Heads, Comp cam 274xe, 650 Double pumper, c4, 3.44 gears. Half a tank a weekend - MPG have no idea - but not much

[danno 128]

Kyle, what is your initial timing, with warm idle and no vac advance? What is the timing when you are maxed out at 2800rpm?

[alphapygmy 10]

351C, Comp 288R solid roller, 750 HP Holley, C-6 ~3000 stall, 3.89 posi, full 3" exhaust. I was getting around 10 mpg before it went up on the jack stands for a drum to disc conversion and some other goodies. Also got a new Gear Vendor overdrive in a great trade. Installed it but haven't driven it yet.

[70Mach03 12]

1970 Mach I with 351C-4V. Has 3.00 rear, long tubes, 670 CFM Street Avenger Carb, Edlebrock dual plain, Pertronix ignition, and a T-5 five-speed from a '94 Mustang GT. Dyno'ed a few years ago at around 250 rwhp. Originally a FMX and got 11-16 mpg. With the T-5 and 3.00 gears I'm at 1800 rpms at 70 mph in fifth. Have gotten as high as 26 mpg driving 65-70 mph on interstate but still hovers around 12 mpg in normal local driving.

[stangme428 33]

I'm prayin' for 20mpg with the 408 clevor and T56..:tt1::crying::yes:

[kyle7713 10]

Kyle, what is your initial timing, with warm idle and no vac advance? What is the timing when you are maxed out at 2800rpm?

 

14 initial and 38 total, vac advance is hooked up too manifold vac not ported.

[LSG 15]

Danno, if you have a 302 and can't get 20 mpg on the freeway, my guess is there is something wrong with it. What carb do you have, and is it running too rich ? What kind of ignition do you have ? Do you have a vac advance ? hooked up to what ? What axle gears do you have ? Do the brakes drag ? Is there fuel leaking anywhere ? An AOD with a 302 ought to get 20+ with zero effort.......what heads did you start with, the 351W heads might be a step backwards, depending on what you had to start with......LSG