How many mpg

[cfan10]

I was wondering if anyone knew approx, mpg for a 84 swb 305 v8, dual exhaust and edelbrock 4 barrel carb.
No recent tune up. Gas gauge not working.

How much gas am I looking at for a couple hundred mile trip?
Thanks for advice.
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[Chris' 86]

I know mine is only getting 10-11 mpg around town. It almost seem like it gets worse on the highway. But, I don't go out of town much in the truck. Can't afford the gas.
86 C10 LWB
305 w/Edelbrock 600
Dual exhaust
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[veinbar]

My '79 SWB had a similar set up. Gas gauge not working in it either. If you know how many gallons your gas tank is, and your Odometer works, that's all you need. Example:

My truck had a 16 gallon tank, so I stopped at a gas station at or before 160 miles just to be safe(10mpg average). When you stop, write down the exact miles you traveled, and the exact gas amount that it took to fill your tank again. Divide the mileage by the gallons of gas, and you have your hwy MPG. Of course, my highway mileage was better than 10mpg but this is how I figured it out. If you're not getting 10mpg, turn around and go home. LOL

I used to get 15mpg with my edelbrock, but I switched to a SMI Q-Jet and now I get just under 18mpg. My engine is stock with the exception of open element air filter and dual 2.25" exhaust.

[veinbar]

Originally Posted by cfan10

I was wondering if anyone knew approx, mpg for a 84 swb 305 v8, dual exhaust and edelbrock 4 barrel carb.
No recent tune up. Gas gauge not working.

How much gas am I looking at for a couple hundred mile trip?
Thanks for advice.
Posted via Mobile Device

Do you know your rear ratio? This is a huge factor in mpg.

[spudz]

Originally Posted by veinbar

Do you know your rear ratio? This is a huge factor in mpg.

you also need to know what transmission you have... But somewhere around 12 most likely

[CaliDude76]

I have an 84 that had a 305, but now has a 350. Same intake and carb set-up since original. Q-Jet 4bbl/350 Trans. I get around 17.5 MPG Highway average 65-70, 75 at the most MPH.. just go easy on the throttle while on the highway.. don't be in a hurry, and you'll do fine

[bucannon]

i have an edelbrock 4 barrel on a 305 with a th700r4 transmission. rear end ratio of 2.73 (which is too slow!)and i average 10 - 12 mpg

and before i fixed my gas gauge i tracked the mileage and could go about 200 miles between fillups. i also always carried one gallon in the bed so when i ran out i wasnt stranded

[DetroitDan]

Originally Posted by cfan10

I was wondering if anyone knew approx, mpg for a 84 swb 305 v8, dual exhaust and edelbrock 4 barrel carb.
No recent tune up. Gas gauge not working.

How much gas am I looking at for a couple hundred mile trip?
Thanks for advice.
Posted via Mobile Device

too many variables to estimate. slight differences in timing or ignition system condition could lose you a couple mpg easy. Tire condition, size and inflation and driving style, aerodynamics of your specific truck, final drive ratio, etc. BUT, a huge ballpark would be 8-12. All you can do is fill up, bring a gas can, and drive until you either run out or make it halfway. Then fill up again and you''l know how far you can go. The calculations listed above (Veinbar) are the best way I know to figure it out.

However, do we know for sure if your odometer works without the speedometer working? I don't think it does on an older vehicle iirc the odometer is driven by the speedo cable. BTW, speedometers aren't hard or expensive to fix. I would do that and a tune up before any trip, if I was worried about it. Good luck

[DetroitDan]

Originally Posted by veinbar

I used to get 15mpg with my edelbrock, but I switched to a SMI Q-Jet and now I get just under 18mpg. My engine is stock with the exception of open element air filter and dual 2.25" exhaust.

HOLY CRAP! what kind of final drive do you have that you can get 18?! I can barely get 15 with my big block, and that takes me two trips! ;>

(That's 7.5 x 2)

[DetroitDan]

[QUOTE=bucannon;4691814]i have an edelbrock 4 barrel on a 305 with a th700r4 transmission. rear end ratio of 2.73 (which is too slow!)and i average 10 - 12 mpg /QUOTE]

that seems really low for a 700r4/2.73. Is it a 600 Edelbrock? I got 10-12 with my 81 rclb K20 with a 305/edelbrock 600, th400 and 4.10 gears riding on 35/12.50 all terrains. Heck, Veinbar over here's getting 18 mpg with his!

[tucsonjwt]

On a big old pickup, 10-12 city, 13-15 highway is what most guys tell me, and this has been my experience over many years. 18 mpg (city or highway) is very unusual, unless you have fuel injection, 1/2 ton, open rear axle ratio, overdrive transmission, etc. My best mpg for a V8 was with a 2010 Sierra Ext. Cab with 4.8L engine and 3.23 rear axle - 15.5 city and 18.5 highway. With a 2000 Silverado 4.3L V6 automatic 3.42 rear axle I got 19 city, 23 highway with very careful driving. You should not expect to get good gas mileage with a big old pickup truck.

[KMK454]

I have a 78 305 V8, 3-speed, 3.07 rear end, truck about 99% stock, stock manifolds, no cats.

11 MPG.

And I drive it 50 miles round trip to work each day, mostly highway 45-65 MPH. Gas is pricey but buying a gas-sipper just to commute is also expensive.

[piecesparts]

I have an 84 GMC SWB, with a bored 383 stroker engine, 700 R4 tranny, 3.73 gears and running 28" tall tires. I get a solid 15 MPG when it is on the highway, running 75 to 80 MPH. You want to gear it so that your RPMs are in the power curve of whichever engine that you are running. The 3.08 gears and 2.73 gears are doing nothing but making it worse, UNLESS you are running a non OD tranny.

[bucannon]

Originally Posted by piecesparts

You want to gear it so that your RPMs are in the power curve of whichever engine that you are running. The 3.08 gears and 2.73 gears are dong nothing but making it worse, UNLESS you are running a non OD tranny.

this is so true. with my 33" ires and 2.73 ratio i cant get into 4th gear without going 85 mph (at 1200 rpm appx.)

[andrewmp6]

Too big of a carb and out of tune carb can hurt your mileage also.

[rayfinseats]

I'm building a gas milage project. 83 chevy 1/2 ton 4x4. 350 or 305 not sure yet, NP208
TH350,2.73, 31x10 tires, headers, edelbrock 600, performer,big open air cleaner, dual exh. Weight down to 4200 LB. Any tips wecome.

[veinbar]

Originally Posted by DetroitDan

HOLY CRAP! what kind of final drive do you have that you can get 18?! I can barely get 15 with my big block, and that takes me two trips! ;>

(That's 7.5 x 2)

LOL! I have found my truck's sweet spot. My 350 is .40 over with flat tops, stock cam, q-jet, th400, 3.08 rear w/ 275/60/15 radial T/A tires. I try not to go above 2500 rpm on the highway (65mph) and i keep my foot very light. Two things I do before any road trip is removed all unused items from the truck keeping only my spare and changing supplies. I also run my tires at the top of their psi rating. It just works. I think the Sean Murphey carb has done the most for my improved mpgs.

[veinbar]

Originally Posted by rayfinseats

I'm building a gas milage project. 83 chevy 1/2 ton 4x4. 350 or 305 not sure yet, NP208
TH350,2.73, 31x10 tires, headers, edelbrock 600, performer,big open air cleaner, dual exh. Weight down to 4200 LB. Any tips wecome.

Gas mileage project out of a 4x4 is a handicapped foundation, but you can maximize it's potential. My vote is 350. From what I've seen, they produce the same mpg avg as the 305, but offer greater hp and torque numbers as well. I would also urge you to consider a Q-jet over an edelbrock carb. my two cents.

[cfan10]

Originally Posted by rayfinseats

I'm building a gas milage project. 83 chevy 1/2 ton 4x4. 350 or 305 not sure yet, NP208
TH350,2.73, 31x10 tires, headers, edelbrock 600, performer,big open air cleaner, dual exh. Weight down to 4200 LB. Any tips wecome.

No thread hijackers!
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[piecesparts]

Originally Posted by rayfinseats

I'm building a gas milage project. 83 chevy 1/2 ton 4x4. 350 or 305 not sure yet, NP208
TH350,2.73, 31x10 tires, headers, edelbrock 600, performer,big open air cleaner, dual exh. Weight down to 4200 LB. Any tips wecome.

I figure that your RPMs will be at 2000 to 2100 at 70 MPH. My guess will be that you are just getting into the power curve of your engine and will need to run around 75 to 80 MPH to get the best MPG. That gear ratio with the 31X10 tires will cost you a lot of power at acceleration from a stop. Unless you drive a lot of hihgway miles and very little city streets, you will be OK, but that mileage will suffer from your starts.

[D13]

Originally Posted by rayfinseats

I'm building a gas milage project. 83 chevy 1/2 ton 4x4. 350 or 305 not sure yet, NP208
TH350,2.73, 31x10 tires, headers, edelbrock 600, performer,big open air cleaner, dual exh. Weight down to 4200 LB. Any tips wecome.

Throw the TH350 and 2.73's away and put in a 700R4 and 3.23's. Better acceleration and much more pleasurable off the line, same or bette net gear ratio. 350 actually will get about the same fuel economy.

#1 key to fuel economy is your foot. I can go from 17 to 23mpg just by tuning the force on the right foot.

[rayfinseats]

Not trying to jack your thread it's the same subject. Thanks.

[cr34t3d_by_d4rkd3n]

Originally Posted by Chris' 86

I know mine is only getting 10-11 mpg around town. It almost seem like it gets worse on the highway. But, I don't go out of town much in the truck. Can't afford the gas.
86 C10 LWB
305 w/Edelbrock 600
Dual exhaust
Posted via Mobile Device

Because your secondaries are opening with the position of your foot, at those speeds you want to be not on, if anything slightly on secondaries...... Time to recalibrate that carb!!... either u have a mechanical secondary carb (mostlikely) if so adj ur linkage via their website howto's (if they still offer that)..... if its vacc, well check all lines, check for proper vacc, and adj if needed..... that what fixed my 620 cfm or whatever it was holley avenger.

Oh! and i get 11 on 91 octane, 75 chevy 350 no smog yes cat converter, stock carb with 71 model jets (5%) larger..... and she still runs lean. Cali no longer offers 93 octane.

[Rightone1974]

I have a 68 gmc C20 with a 351m big block v6. What kind of mileage should it get on the average. The truck is bone stock.

[1977K10]

I kinda have the same problem.. the prior owner didn't take care of the 77 I have and he cut the wires between the tanks and the fuel gauge. I am doing what the guys are saying, I write down my mileage every time I fuel up and do it that way.