Best MPG for a 2wd 67-72

[shelby987]

I am going to try and start two threads here, not really a poll, more of looking to set the bar for MPG (which seems to be a big topic of discussion these days).

I wanted to know what is the best MPG you have gotten with your 2wd, and what your setup was....Tires, Ride height, rear gears, transmission (manual/auto...OD?), engine (details such as ele. fan, carb/efi/tbi, exhaust, hei, etc). I know there are people on here with small V8's, I6's, V6's, Diesels, just trying to see what combinations produce the best results.

I don't want to turn this into what doesn't work, we all know how to get below 15mpg.....we all know how to get 4mpg!.....lets try to stay on topic as best we can.

[SB406]

'71 short box
small block 406, TBI, Vortec Heads,RV Cam, custom (home-made) chip, clutch fan, Stock Exhaust Manifolds, Dual Exhaust, 700R4 auto trans (OD), 3.42 rear gears, 255/70 R15 (~28" tall) Rear tires. Standard Ride Height. No Bed cover, MSD 6a & blaster coil.....

87 Octane
16 MPG City / 21 MPG Hwy

[Robert1970C20rstbukt]

350 w/ points, 7mm wires, R45TS plugs, stock air breather setup, thermo clutch fan,1976 Q-jet, original cast iron intake, 1.94cc camel hump heads. Grandpaw rebuilt the engine in 1978 or 1979. Has a TH400 out of a 1967 Caprice, I've never done anything to it other than change the fluid and vac. modulator, it'll get a new torque converter soon. Rear is the Eaton/Corp. 10 bolt full floater with 4.10 gears running 33-12.50-16.5 BFGoodrich A/T's. Has a 2 1/4" dual exhaust with 18" glasspacks dumping underneath the front of the bed. It got about 11-12MPG on the highway before the dual exhaust and new tires, should get a little more now.

[WizzKidd!!]

71 LWB, newer (90's?) 350 (i know it has 86 and later cast iron heads), TH350, Edelbrock 600cfm, performer intake, headers, dual 2 1/4 exhaust w/ flowmasters, 31' wildcats (pretty much bald), and unknown gears. I go about 55 @ 2000rpm in drive if that helps...

Adjusted for speedo being off I get about 14-15 mixed driving.

[junkyardjohn]

11.... 12 If I'm Lucky John

[see ten]

14.75mpg out of my C10. 350 engine, Th350 trans, 3.08 gears. Engine driven fan removed and replaced with electric. HEI with MSD coil and wires, edelbrock intake, roller tip rockers and March Performance underdrive pulleys.

[355]

16+ at 80 mph, 3.07 gears,255/70 tires/ 700 r4 w/od and lockup, 355. you can read the rest in my signature.

[Shane]

I haven't put any gas in my '67 in over 5 years ...

[Roachgod]

Whoops my fuel slowly leaked out last weekend after we pulled the vortech 350 out of her so for now 0 mpg without even a motor. I'll post hopefully next weekend if I get the time to drop my new 454 in there.

[jku72]

I'm getting 18 highway with my suburban. The thing is that most people make modifications that increase power without thought to what it does to efficiency or mileage. It sort of makes sense, cause if you want great fuel mileage, you'd buy a small car.
But, for stubborn people like me that want to drive the old trucks, yet still not get terrible fuel mileage, there are things you can do. The big items that improve mileage are gears, headers, and higher compression ratio.
The big killers of mileage are usually high performance cams, deep gears, and big bore carburators.
Even if you put an overdrive in a truck, the big cam and carburator still kill you.
The reason 292 6 cylinder trucks don't get good mileage is the low compression ratio, great for longevity, but hard on gas. Even the 250 6's are much lower compression that the v-8's. (of the time). One of the things that I notice is that the new crate 350's are low compression engines, e.g. they will never be efficient. Lower emissions, but suck the gas.
The reason diesels are so great is the big compression.
My thinking on a good mileage setup, that still made decent power:
283 with around 10-10.5 compression, aluminum heads, stock cam, HEI, small tube headers, quadrajet carb(primaries are smaller than even a 2 barrel), 3.42 rear end, and an over drive trans. If no overdrive, then I'd run either a 3.07, or if you had a sm465 4 speed, I'd run a 2.76 rear gear.
My current burb has 10:1 compression 350, iron heads(not stock, they are from a 1969 or 70 camaro) stock cam, q-jet, HEI, sm465 trans, and a 3.07 rear gear. Thats with a crappy single exhaust coming off iron manifolds. It makes good power down low, and cruises nicely, although the overly restrictive exhaust drops the mileage quickly over 70 mph.

[Josh]

Best I've netted on my 69 was 18 highway @ 70mph. I achieved it with a qjet, the stock cam/bottom end, set of 487 large valve heads, old camaro SS factory performance intake, good HEI, a fresh tune up, 235/75/15 tires and 3.07 gears. Engine has around 9.5:1 CR and pulls good down low just lacks a lil top end The best I can manage in the city if I keep my foot out of it is 14mpg. Otherwise I get around 12mpg..

[71chevytruckguy]

'69 swb, '86 305 with q-jet carb, offenhsauser dual port intake, comp 268h cam, flat top pistons, hei, accel 300+ plug wires, accel shorty header plugs, flowtech headers, running on 93 octane, 2 1/4" dual echaust with flowmaster 40's. trans is a 4 spd saginaw, 3.43 rear gears, 275/60/15 tires, lowered about 2"/4". best mpg is 12 city and 20 highway. chris.

[396C20]

I just checked this morning. I got 13 mpg combined city and hwy.

69 LWB, fresh stock type rebuild of the 396 with the exception of Comp 254 advertised 4x4 cam, MSD Hei, Holley quadrajet replacement carb with the black spring in the vacuum secondaries (it opens the secondaries at a higher rpm), stock manifolds with full length 2 ½ in dual exhaust with an x pipe. Stock suspension and ride height 245/75/16 tires.

[TP from Cntl PA]

Got 15 or so with the 350 in my '71 C-20.............Put the Cummins in it, and it doubled and then some! No highway use, just two lane black top and gravel roads/lanes.

[Buckman]

2wd 71 with a 355 w/700r4 od. Mix I get about 14-15, Hwy I get about 16.5.

[pumper578]

not really bragging but i get about 13-14.5 MPG, but my speedo doesnt work so i am just guessing ( 56 miles to and from work and 4 days = 224miles/17.5 gallons= 12.8 MPG)

[carl609]

67 long bed, lowered, but not enough, 275/60s in the back and 245s in the front. 350, 286h comp cam, roller rockers, big valve heads, holley two barrel, th 400, 3.73s. I built the engine for a street stock race car, so mileage wasn't a concern. Even with the 2 bbl, I am lucky to get 10mpg, more like 6-8. I have a fairly heavy foot though.

[Goose]

'72 GMC step 350/350; 3.08 gears, 600cfm Edelbrock;mild build on engine runs on 87Octane, headers; lowered slightly, Checkmate bed cover; and 235/60/R-16's rear. Ave. 11.5. I saw 14 once with a good strong tailwind.

[Huck]

My 72 cheyenne with crate 350, stock intake, HEI, 5speed, 307 posi, would get 18-20mpg hwy. Things that hurt it--edelbrock intake and headers!! Things that really helped it==edelbrock carb, 5speed, bed cover.
My 2000 Silverado 4x4 extended cab gets 20-21 hwy with 373 gears and bed cover. The bed covers show 1-2mpg improvement!!
My wife's 06 Honda civic==40mpg!!!
My daily driver Cavalier convert ==25 in town and 30hwy.

[Greubin]

Here's mine, I'm still tuning..

'71 C20 w/ crate 350 290HP, HEI, Edelbrock 1406, BTO 700R4, 4.10's and dual exhaust. With about 1000mi on the eng/trans I'm getting 12mpg mostly commuting. I've heard the 1406's run rich so I need to check into running smaller jets / tuning carb. Plugs are tan though.

[Greubin]

Originally Posted by Greubin

Here's mine, I'm still tuning..

'71 C20 w/ crate 350 290HP, HEI, Edelbrock 1406, BTO 700R4, 4.10's and dual exhaust. With about 1000mi on the eng/trans I'm getting 12mpg mostly commuting. I've heard the 1406's run rich so I need to check into running smaller jets / tuning carb. Plugs are tan though.

I'm up to 15mpg, rejetted carb, adjusted float height to spec and connected vac advance pod to "ported vacuum".

[Green Machine]

18.2 MPG some town, mostly highway untuned from 1970 C10 LWB, 89 Camaro 305 (was TBI) with stock roller cam and swirl port heads. Performer 2104 and Edelbrock 1406 stock jetted(so far). Ram horn manifolds and crappy duals. 3.73 posi with 265/70-17 tires and 4 speed manual with .73 over drive. 60 mph=1700 rpm.

Will add headers, better exhaust, tune the carb and tweak the dizzy this spring. Hoping to beat 20 mpg.

[BCOWANWHEELS]

well i got a 1971 c10 with 286000miles on it.it has a stock 250 6cyl, 3 on the tree, 235r15 tires and at 60 mph it gets 14.5 mpg loaded or empty. 65mph it goes down to 13.8.

[Goose]

I have the 1605 as well - what size jets did you end using? What RPM are you turning to get 15mpg? Did the leaner jets affect your acceleration performance? Thanks.

[bazkook]

Not to get off subject here but I plan on putting a Ram Jet 350 crate motor in a 70 C10 I'm about to fix up. What kind of gas mileage could be expected with a 700R4 and either 3.73 or 3.42 gears?