How many MPG should I get?

[72cheysuper]

I was just looking at the mpg poll and was wondering... since I just bought my truck and really dont know. What kind of milage should I get? And what mods can I make to the truck to see a real difference? With gas prices going up faster than Mr. Bush could ever have hoped for, It is a concern.
My truck is a 72 lwb half ton, 350 4 barrel, automatic, ps, pb, air, cruise control, posi rear end (although I dont know the ratio), single exhaust. It had a complete engine overhaul 1000 miles ago and a new carb. It runs great but seems to run a little rich. Im guessing it currently gets about 13.

[haysonj]

Mine is getting 12 with 4.09 gears, 35 inch tires, and an overdrive, that's why I'm adding fuel injection. I would like to get 15 to 18. On yours a tune up will help but these trucks just don't get very good mileage.

[67_C-30]

I get 15-16 in my 69 C/10 SWB with a 350 Q-jet/TH350 and 3.08 gears.

[68gmsee]

Welcome to the board.

When my 69 was running (350/350) I was getting 13-15 on the highway with no A/C. Never checked for strictly in town driving that's where the lower figure comes in.

fyi: CONTENT REMOVED BY MOD
*EDIT*
No political talk on 67 - 72 chevy trucks.

[72cheysuper]

Originally Posted by 68gmsee

Welcome to the board.

When my 69 was running (350/350) I was getting 13-15 on the highway with no A/C. Never checked for strictly in town driving that's where the lower figure comes in...

Thanks for the welcome!


Edited to remove the political comments from the quote, and the response to it.

[72cheysuper]

67 C 30,
Are you running dual exhaust? 15 to 16 mpg sounds pretty good!

[Longhorn Man]

72cheysuper... welcome to the board.
First, sorry I had to edit your post... it wasn't what you were sayin, you replied to the comment above yours... which was posted by someone who should know better. (no politics on here, it ALWAYS goes south) We've tried to let it in the general discussion, we even had a specific board for it... but it simply doesn't work.
Now... back to the original topic... 13 MPG isn't bad... esp when you consider you live in hill country. You can try to tune a little more into it, but in reality, you are doing slightly better than average. In order to do anything that would net you impressive results, you will end up spending some decent chunks of cash.
Your gearing, assuming it hasn't ever been messed with, would be a 3.07 with that engine and tranny combo.

[1bad chevy]

don't try a 500 caddy power plant with 4.10 gear's as the mpg are only 6 at most soon to be 3.08 which should help out considerably (i hope) lol

[72cheysuper]

Originally Posted by 1bad chevy

don't try a 500 caddy power plant with 4.10 gear's as the mpg are only 6 at most soon to be 3.08 which should help out considerably (i hope) lol

Caddy power? Do you own a gas station?

[72cheysuper]

LONGHORN MAN,
Thanks for the welcome! I see your from Columbus. Know the area well, being from Chillicothe. Hey....thanks for the edit! I can see why politics arent allowed here, and why it doesnt work. My apologies to 68gmsee and anyone who may have read the threads.
(Back to the topic) This truck was previously owned twice. By the man I bought it from and his neighbor. From the records I found in the glovebox, it had excellent mechanical care. I believe the rearend to be original. I ran it 70 mph through the mountains of tennessee and the engine didnt seem to labor at all. The only thing I really noticed was how it sounded congested through the single exhaust. Im wondering whether I should convert it to dual exhaust and if the mpg would benefit?

[HomerJ]

Originally Posted by 1bad chevy

don't try a 500 caddy power plant with 4.10 gear's

Thanks for the tip!!!!

Originally Posted by 72cheysuper

I was just looking at the mpg poll and was wondering... since I just bought my truck and really dont know. What kind of milage should I get? And what mods can I make to the truck to see a real difference? With gas prices going up faster than Mr. Bush could ever have hoped for, It is a concern.
My truck is a 72 lwb half ton, 350 4 barrel, automatic, ps, pb, air, cruise control, posi rear end (although I dont know the ratio), single exhaust. It had a complete engine overhaul 1000 miles ago and a new carb. It runs great but seems to run a little rich. Im guessing it currently gets about 13.

72cheysuper,

I have a 67 with very similar specs to yours. I was getting 10MPG in mine and - like yours was running very rich. I had put an Edelbrock 600 on top, which I got from ebay. I only had time to do a basic rebuild on the carb before putting it on the engine. A couple of weeks later, I got a tuning kit and a wide-band o2 meter and started tuning it to optimize the AFR at idle and cruise. I found that the PO of the ebay carb had it calibrated about as rich as it could be. With just a very little tinkering, I got up to 13.5. Soon after that, I yanked the engine out and had the body media blasted, so no further tinkering since.

Your carb may not be as far off as mine was, but it may be worth your while to invest in either calibrating it or (as BILLLA preaches, with good reason), spend a couple hundred to have good shop tune up your engine completely.

HomerJ

[Longhorn Man]

I would do daul pipes personally, but the MPG gains would probably be marginal at best. I've HEARD of gains of 1 MPG, but also heard of losses in this department. I personally contribute any losses to a heavy right foot and a driver diggin the rumble of low restriction mufflers.
If you are from Ohio... what did you do to deserve moving to WV? LOL... I'm just messin. I'm glad you understand the political thing... some people just don't get it and continue to push it.
As for the caddy 500 comment... I think 1 bad chevy needs to do some seriouse tuning. The cad engines produce gobs of torque which usually makes better MPG... even with the gearing you mentioned (look in my siggy). Before I had this 425, i had a 500, and I was getting 12 MPG on the freeway at 70 MPH. This one I could probably tune to 15 if I were to try, but I simply haven't tried. There is a massive oil leak up front, and in all honisty, I've been too lazy to take car of it, so it pretty much stays on the surface roads all the time.

[72cheysuper]

Originally Posted by Longhorn Man

If you are from Ohio... what did you do to deserve moving to WV? LOL....

Yeah....yeah... know. I get that alot. When I decided to go east......I should have kept going til I heard the roar of the ocean. I used to live in Columbus. Nice town. One thing I have noticed about Parkersburg is that there doesnt seem to be many classic or antique vehicles around. Probably due to the strict inspections here. When I drive the 72, people stop what they are doing and stare like its a parade float going down the road. Kind of funny actually.

[samwise68]

i'm pulling a constant 15-16 with my '69, and on the last fill-up, bested to 17 mpg.

all stock, except for headers. 2 bbl, 307, 3 on the tree, and 3.07 gears.

-Sam.

[72cheysuper]

Im sure that 3 on the tree helps with the mpg...or...dooooes it? I was looking at your build thread....burnouts, cherrybomb rabble...lol.. j/k. With all the work you have put into saving that $100.00 beater, you deserved to thrashed it a little. Looks like youve brought it a long way. Keep up the good work!

[piecesparts]

If you take a look at some of the different trucks/cars on the road today and their touted MPG figures, you will see some defining things that stand out in their numbers. The very first and most notable is that the MANUAL OD trannys get better mileage overall. The auto trannys (with OD) get good numbers and you can gain by doing one in your truck, BUT the real change would be to go to a 5 speed or 6 speed tranny behind your engine. That is due to the manual tranny eliminating the torque converter slippage.

The other things to be done with your truck is to match the components as best as you can. What cam is inthe engine? Did the builder put in to much cam, or is it good for your RPMs that you run on the road. This will decide your final gear ratio and that is costly, but worth the thought processing. What tire size do you run? Are the tires too big or too small to keep the RPMs aligned on the road. This will be necessary to think through with the gearing problem. (IMPORTANT: What RPMS does the engine run best at and it seems to be the most stable) That is going to be the SWEET spot in your endeavors.

The statement that you think the engine is running rich----When do you smell it the most? Is it associated with the idle circuit and is the idle running a little high for normal conditions? That may be cam related AGAIN. That possibly means that the builder put in a slightly radical cam and the carb's butterflies are sitting in the "Transition area" from the idle circuit going to the Power circuit. That is where you will have to think a little bit, do you wnat the performance of the cam or do you want economy. IF it is part of the problem, then a possible solution woud be to step up on the torque converter's stall numbers and the idle would settle out to a better number. THEN AGAIN--you may just need to adjust the carb to match your needs.

Where is the timing set at? Having advance in your timing circuit helps on power building efforts and tends to lead to a more economical engine performance. Don't run the timing adjustments too low, it builds heat and works the engine more. A good air filter setup (preferrably low resistance) and a good dual exhaust will help on performance and thus allow for less work to get acceleration or daily performance--this helps in overall gas mileage. If you want to burn every ounce of that high cost dinosaur blood, then look at getting a "Multi-spark" setup to enure that you are getting the complete burn in each of your cylinders and using all of the gas that you can instead of pouring unburnt fumes out of the tail pipes.

Have you looked at a bed cover, this will give less resistance to wind and help on daily driving. Look at tires that have lower rolling resistance for mileage. Lowering the truck gives less wind resistance under the frame and allows for better cruising. Think like a NASCAR team on this.

[72cheysuper]

Originally Posted by piecesparts

What cam is inthe engine? Did the builder put in to much cam, or is it good for your RPMs that you run on the road. This will decide your final gear ratio and that is costly, but worth the thought processing. What tire size do you run? Are the tires too big or too small to keep the RPMs aligned on the road. This will be necessary to think through with the gearing problem. (IMPORTANT: What RPMS does the engine run best at and it seems to be the most stable) That is going to be the SWEET spot in your endeavors.

The statement that you think the engine is running rich----When do you smell it the most? Is it associated with the idle circuit and is the idle running a little high for normal conditions? That may be cam related AGAIN. That possibly means that the builder put in a slightly radical cam and the carb's butterflies are sitting in the "Transition area" from the idle circuit going to the Power circuit. That is where you will have to think a little bit, do you wnat the performance of the cam or do you want economy. IF it is part of the problem, then a possible solution woud be to step up on the torque converter's stall numbers and the idle would settle out to a better number. THEN AGAIN--you may just need to adjust the carb to match your needs.

Where is the timing set at? Having advance in your timing circuit helps on power building efforts and tends to lead to a more economical engine performance. Don't run the timing adjustments too low, it builds heat and works the engine more. A good air filter setup (preferrably low resistance) and a good dual exhaust will help on performance and thus allow for less work to get acceleration or daily performance--this helps in overall gas mileage. If you want to burn every ounce of that high cost dinosaur blood, then look at getting a "Multi-spark" setup to enure that you are getting the complete burn in each of your cylinders and using all of the gas that you can instead of pouring unburnt fumes out of the tail pipes.

Have you looked at a bed cover, this will give less resistance to wind and help on daily driving. Look at tires that have lower rolling resistance for mileage. Lowering the truck gives less wind resistance under the frame and allows for better cruising. Think like a NASCAR team on this.

Man.... have you gave me alot to think about... Very cool. Im not sure about the cam. Im guessing close to stock. I dont really smell an odor, but instead see the black smoke pour out the tailpipe on start up. The engine idles very low imo. I have resisted the urge to adjust the idle up until I find out where the timing is. While on the subject of timing, what is your take on electronic ignition vs. mechanical? My dad has a fiberglass bed cover that isnt being used and the thought did cross my mind. It is very heavy though. Dropping the truck and dual exhaust are in the near future I think. I also have a set of 15 ralleys that I think I'll swap on. Thanks for the great ideas!

[piecesparts]

Originally Posted by 72cheysuper

Man.... have you gave me alot to think about... Very cool. Im not sure about the cam. Im guessing close to stock. I dont really smell an odor, but instead see the black smoke pour out the tailpipe on start up. The engine idles very low imo. I have resisted the urge to adjust the idle up until I find out where the timing is. While on the subject of timing, what is your take on electronic ignition vs. mechanical? My dad has a fiberglass bed cover that isnt being used and the thought did cross my mind. It is very heavy though. Dropping the truck and dual exhaust are in the near future I think. I also have a set of 15 ralleys that I think I'll swap on. Thanks for the great ideas!

The long bed will complicate some things in your efforts to find a good balance in what to bolt on and what you actually need to go further in MPG gains. The hard tonneau has some set backs that you need to consider: What do you do with the cover if you have something big to haul? What does it really weigh and are you gaining with it. I have a hard tonneau cover on my show truck and it does more good for me, than what it's weight hampers me--BUT I don't haul much with that truck. MY daily driver has a soft tonneau cover and it can be rolled up at ANY time and provides me with a covered bed to use during winter or rainy days. A soft cover on a long bed is not a good look for me, but if it works, then the gain is the plus. I would look for one of the 3 section light weight covers for your truck if it was me.

What do you have for a distributor, now? Is it the original or is it an HEI replacement? For the money, I would do something like a programmed HEI ( I got mine from The Carb Shop) and they set it up for my cam and engine. I purchased a billet reman from them at the about the same cost a standard HEI would run and it works great. While you are at it, look at 8MM low resistance wires, that change is worth 10 to 12 HP on an average and a good high performance coil. I am running MSD spark plug wires and the price is comparable to many other brands.

[Longhorn Man]

only thing I'll add to that, auto overdrives have no slippage in the converter once you are up to 45 MPH or so, when they go into lockup

[piecesparts]

Originally Posted by Longhorn Man

only thing I'll add to that, auto overdrives have no slippage in the converter once you are up to 45 MPH or so, when they go into lockup

I agree the lock up convertor will set, but there is still slippage in that tranny and that is where you loose the milae over the manual. That is a given, as is noted by gas mileage numbers from the newer GTOs, Camaros, Corvettes, Mustangs, ETC....

[WorkinLonghorn]

From the original post;

It runs great but seems to run a little rich.

I didn't read the whole thread.If you have evidence of richness,then that would be the very 1st thing I would fix,and it's NOT the idle mixture screws that are going to help. You need to find out the cause,ie.clogged air filter,worn or incorrect jets,metering rods too small,leaking carb,high float level,choke not fully opening,etc.

[jimmydean]

12mpg regardless.

[Longhorn Man]

...look at 8MM low resistance wires, that change is worth 10 to 12 HP on an average and a good high performance coil..

I would bet my next pay check, that on a stock or dam near stock (as he has indicated) engine, this would gain a horse MAYBE two... over good 'normal' wires and coil.
And since he is actually looking for MPG, here... I doubt it would do anything at all.

[piecesparts]

Originally Posted by Longhorn Man

I would bet my next pay check, that on a stock or dam near stock (as he has indicated) engine, this would gain a horse MAYBE two... over good 'normal' wires and coil.
And since he is actually looking for MPG, here... I doubt it would do anything at all.

Whatever you believe. It made a serious difference on my 91 DD and there are not many that get 20 MPG with the throttle response that I have on a weak-willed low HP 5.7 TBI motor. I noticed serious improvement on the wires and the coil install, which was not there prior to the change. But I may be wrong----


By the way getting rid of the belt driven fan, IS worth a gain of a MPG. Seen it in more than one application.

Improve HP, Improve engine response, Improve MPG--because you are getting what you want with less gas pedal application...once again--I could be wrong... I put 20,000 miles on my truck yearly and it sees all kinds of weather, highway, and city driving. The TBI is part of the mileage for the 91, but I also have a 385 CI stroker motor in my 84 GMC show truck that is getting a good 15 MPG with 3.73 gears W/O a lockup converter on the 700R4 tranny and low profile tires. The top picture is the stock 5.7 motor in the DD and the one below is the stroker motor.

[cobb_ben]

Millage in these truck you dont worry about it! LOL. More like gallons per mile... They way to get good millage with a classic truck is new fuel injection, overdrive and decent gears.