MPG poll

[Orange]

Average is about 7mpg - staying "out of it" most of the time.
Engine is the original 1971 GMC engine that has been built following:
.030 over (355ci)
Heads Reworked Incl.(1.94 In./1.55 Ex. Valves)
.458" Lift Crane Cam / 292° Duration
Dynomax Full Length Headers w/ 2-1/2" Exh. with Single Chambers
Edelbrock Performer RPM & 600 CFM Carb.
350TH Transmission
Stock Gearing (3.73 I suppose?)
30.7in diameter rear tires (285/70/15)
Chrome Valve Covers & Manufacturer Stickers covering the back bumper.

Nothing else effects gas mileage too much that I can think of.

(Just kidding, the manufacturer stickers aren't on the back bumper, but if they were, chalk up an extra +10hp and 3mpg).

[Longhorn Man]

orange, if your truck came with that Th350, and there is nothing else listed on the SPID label..you'll have a 3.07 gear in there if it is a c1500... if it is a 2500, with the auto, then a 4.10 is standard.

[Orange]

Originally Posted by Longhorn Man

orange, if your truck came with that Th350, and there is nothing else listed on the SPID label..you'll have a 3.07 gear in there if it is a c1500... if it is a 2500, with the auto, then a 4.10 is standard.

It is a 1500, and the TH350 that is in it is the original.
I wish the idiots who painted it wouldn't have so carelessly ripped off my label, but they did. And they also lost the pictures that I took of the entire build, which included that label. So I really don't know. I'll have to crack the case to find out for sure I guess.

It honestly feels a little bit shorter than a 3.07 - brute low end torque, and higher RPM on the interstate (I know my cam and trans don't help this any, but still...)

[Indyuke]

Voted in the 15-17 range. Mixed city and highway gets a little over 16mpg for me. Stock 350 with a q-jet, 700r4 trans, 3.73 rear and stock size tires. I grit my teeth every time I buy gas, but I guess it could be worse. *sigh*

[72 CustomCamper]

Talk about an old thread. Last post was almost 2 years ago...


Chuck

[69long"n"low]

I no i went in to the mpg thread and From this year, and longhornman posted to this poll i thought with the gas prices id like to know what everyones getting and what their doing bout it

[LONGHAIR]

Newbies almost always bring up the old threads and the oldsters usually don't realize it right away.

[Longhorn Man]

well, I did link to it, and when I do that... it tends to come back up.
I think the results on this poll are good reference points.

[49m]

I voted 13 to 14 MPG ... Yeah... I'm doing OK . I have a stock 350 with a 3 speed with overdrive and 308 gears

[69GMCLonghorn]

11-12, 69 2WD Longhorn, 32" tires, built 350, headers, Magnaflow exhaust, holly 600, big cam, SM465, 4:10 corporate rear end, 3100 RPM @ 70 MPH.

[Ackattack]

I got 18.5 mpg out of my 72 GMC LWB. It was running a TPI 350, 700R4, and 3.73gears. It also had headers, 2.5" exhaust and a few other things. Nothing wild though.

[samwise68]

last fill up was up to 17 mpg, but thats a first, usually it's sitting right at 16-16.5.

tired 307, 2 bbl, headers, 3 on the tree, 3.07's out back, running 235/75 all the way around.

everything is stock. and with the *close* to stock height tire, I know the speedo isn't off. so, yeah.

Kind of a dog out of the hole, but love to stretch those legs on the highway.

Oh, and driving style...like a complete idiot.

-Sam.

[chevelle]

I have been gettin about 19mpg. 350 TBI, 700r4, nothin to crazy. oh yeah and im always on the highway

[69GMCLonghorn]

Samwise68, hang on to that 307!! I've had a 69 3/4 ton, 307 4-speed, and a '71 Chevelle, 307. They are great engines. Yeah, the 350 has more cajones, but the '69 truck is owned by my neighor who beats the hell out of it and now has over 400,000 miles and just replaced the second motor (not too bad!). My Chevelle used to get me 17 MPG in mixed city/highway and 19 on a good highway run.

And "chevelle", you are further proof that it's all about gears!

[Long Roof]

My 4x4 Jimmy gets about 9 mpg and that is almost all city driving. It has a stock 307 with performer intake, 600 holley carb, headers, dual exhaust, 350 hydro tranny, 4:56 gears, 36x12.50 tires (34.5" tall actual) and NO top. At 55, I'm at about 2450 rpm. If I had a 50/50 mix of city highway I think I could get about 11 or 12 mpg.

[tim21391]

im getting about 7-9 a gallon....402 big block..400 turbo...holley carb...i get bad mileage because i am missing on 2 cylinders and havent had time or money to get it fixed yet... and i have lfs (lead foot syndrome)

[dan42]

Originally Posted by Longhorn Man

yeah, I'm planning a move out west too...where insanity meets the sea. (LA)

You know, I think the gas out here is crappier then it is in most states - I have driven to Arizona and as soon as I fill up over there, my mileage goes up. BTW, are you kidding about moving, or just a little twisted, or both?

[snj8198]

12.5 last tank, mixed city/hiway.

[Longhorn Man]

woah... that's a quote from a long time ago.
No, those plans have been killed, burried, and all but forgotten.
I would love to live in southern cali... however, on my last visit, I saw it for what it is, and I lknow I would never in a million years be able to make it there.

[Blue_71]

best ive gotten out of my k20 was a tad over 16, all interstate

normally driving to work and back everyday i get 12.5. it gets right around 12 loaded or unloaded, hilly or flat. 1998 350 from a 1 ton, LT1 hydralic roller cam, 89 tbi heads ported and polished, stainless valves, stock ported intake, stock 350 tbi, double roller timing chain

i also voted on at less than 7... when i used to drive the 69, it got 4-6, with a best of 11.4 on the way to the 1st national board meet. that was with 0 psi compression on one cylinder and a cam way to big for any stock engine, and an edelcrock carb im hoping to hit 15 when i get done rebuilding it

[dan42]

I'm not sure what mine really is, but here's the new gauge I'm putting in the truck:

[ratpackv8sonly]

Befor I blew up my forth 700-R4 I was getting 19 mpg on the freeway with 4:11s and a 383 stroker, Q-jet. Now when I installed the 4 spd and 900 cfm Tri power it went to GPMs!!! Tripower has now been sold and a new set of heads and back to my Q-jet. The 4spd is still in it but its only been around the block so dont know what it gets now. Getting ready to install a 2:75 set of gears in it. By the way it is a 9 inch ford axle.

[ksjh1316]

12 on a good day running a 292 4 speed with a 4.10 posi rear. This tank is slow and loves to drink

[69ShortStep]

I voted 15-17 mpg. Last 2 fillups I have gotten 17+ running 250 with hei & monojet, 3 spd, 3.08 gears and 275/60/15 tires.

[blukangoo]

Not bad how the new guys find the old threads. Almost 3 years old.

I need 19 Liters evey 100 Kilometers???
On the net I found some converters and they all come to 12.3 MPG.

I have a 327 with a 400 Turbo 3 Speed Automatic and a 1407 Edelbrock Carb.
I have a 12 Bolt Rear End but am not sure what gears I have.