higher MPG

[bucktruck68]

Hi all, I'm new to the site and think its a great place to spend some time reading and viewing pix of everyone's trucks. I have a 68 Custom 10 that my dad bought brand new in 68. His first new vehicle. Before I could drive (78) he and I overhauled the engine (307) and I started sanding the body for a new paint job. That was my pride and joy by my Senior year. He gave me the truck when I graduated HS and I drove it to college and work until about 89. Since then it has pretty much been sitting. He has it at his house but I am about to bring it to mine where me and my son (11) are going to get it back up and running. My dad has done a lot of body work to it over the last few years. The engine still runs but I'm sure it will need some work. Lots to do and a lot of things going through my head on the direction I want to go so I'm using this site and everyones's experiences to help in that decision. It has 3 OTT and I'm debating whether to keep it or go to an automatic. I like the 3 OTT but I get 9 mpg and I am not sure I want my son having to deal with a manual in the amount of traffic I have around me. Sorry for the long intro but thought you guys might want to hear my background. Here's my question. What transmission/rear end combo would get me a lot better mpg than the current one? Thanks for your comments in advance.

[N2TRUX]

Welcome to the forum bucktruck68. Thats a great background story on your truck and its good to know you are passing the tradition on to your son.

We really need to know more about the truck to offer the best advice. If improved MPG is a priority, lets start by looking at your rear gears. If its a 4.10 set then a gear swap would be worth the trouble. To determine the best ratio, we would also need to know what size tires your running. Too tall a tire with to short a gear will kill MPG as well.

I would look at these first then consider an AoD such as the 700r4 if you still want to go further in your quest.

[hugger6933]

I have in my shop right now a 70 with a 327 and a 3ott. I am heavyily thinking about adding a t-5 5 speed to have a overdrive. The auto thing has been done to death. I have two others of this style truck and one is a big block and the other will have a smallblock both with autos. So, to be different , I am thinking of the t-5 to the piont that I have bought one from a v-8 camaro and a S-10. Look ath the FAQ section there is a write up on it. But, if driving much in town with a teen driver is gonna happen I think you might want to go auto. Look into a 700R4 or a 200r both have the overdrive that will be neded to get better mpg. The tune of the motor is impearitive to get the best mpg's timing set right valves set right carb set up right andas mentioned the rear gearing is factored in as well. If you have 4:10 gears just to drive around do you really need it? your son may think so when he romps the throttle. Higher gears like 3:42 or even 3:08 make more sense. Welcome to this site!

[LMN8UR]

HEI ignition, Edlebrock performer intake and 4 bbl, and a air/fuel ratio guage for tuning.

Look for a NP-833 (MY6) out of a 81-87 truck. It's a direct bolt up (Minus the whole in the floor for the shifter). I got mine of eBay for less than $400 w/shifter!
With the 307 I certain wouldn't go as radicly low as my 2.76 rear, but the Overdrive is great!

I've actually broke 19 mpg with my old 350, and since I put the 383 I haven't gone on any road trips but my mileage around town and to work and back (20% city / 80% Hwy) my mileage is between 12 to 16 (Depending on how mant HEMIs I eat!). . .

Good Luck.

[Lee H]

Your biggest bang for the buck to increase milage is a good old fashioned tune up. I'm talking a real tune up, new plugs, wires, distributor dial in, carb rebuild. Not one of those look at the engine and say everything looks good tune ups. After you get a good baseline then it may be time for parts swapping.
Posted via Mobile Device

[WorkinLonghorn]

I second what Lee H says above because I drive a stock '69 with a 350 and a stock 4spd (only use 2-4 usually) with a curb weight of over 5300 lbs. with all my tools onboard and I get about 12 MPH no matter how I drive or what I haul in the back. So your 9 MPG means to me that something is way off.
WLH

[cdowns]

suspension tires and lubrication are all good ways to increase mileage that are often overlooked

[fastwillie 696969]

add a k&n air filter will increase power and mileage ,headers will increase p and m ,mufflers too,dont forget to add a tornado http://tornadoair.com/turbosuperapplications.htm

[Longhorn Man]

K&N is great for wearing down your bearings and cylinder walls due to the added dirt going into the engine.
Tornados have been proven to do nothing but drain your wallet.

[longbed67]

Originally Posted by Longhorn Man

K&N is great for wearing down your bearings and cylinder walls due to the added dirt going into the engine.
Tornados have been proven to do nothing but drain your wallet.

Couldn't agree more if you dont believe look up some peer reviewed research studies on it!

A good Tune Up the engine for sure using a wideband setup and monitor and depending on how much you romped on the engine when you drove it maybe complete a rebuild... I would definitely go with a stock 3.07 gear ratio or a 3.08 Richmond ring and pinion, and around a 30"to 31" tall tire in the rear even with a final drive of 1:1 on the tranny that will still get you down to some nice cruizing rpm's if you want to play around with different combinations go to
www.12bolt.com and go to the gearing calculator it is an easy to use excel file and allows you to put different tire sizes transmission and rear axle combinations and gives you a spreadsheet of everything you need to know. it is by far the easiest and best gearing calc I have ever used.

[oldgold70c10]

Originally Posted by Longhorn Man

K&N is great for wearing down your bearings and cylinder walls due to the added dirt going into the engine.
Tornados have been proven to do nothing but drain your wallet.

Can you elaborate?

[68gmsee]

Welcome to the site... All good responses above.

My experience with these old trucks that I've been driving since I turned 15 in 1958 is that you're not going to get very good gas mileage out of them. Yes, you can go from 9 to 12, 13 maybe 15 mpg with a tune up, rebuilding the engine or changing rear ends and transmission but that's still bad when gas is $3-$4 a gallon. For a youngster that means having to spend quite a bit of money just to go to school unless you live couple of miles from the school. My nephew found that out real quick. His part time work money was going strictly for gas.

You could modernize it to the new computer controlled engines and that would help or you could leave the truck the way your dad bought it so that the younger generation can experience what we old folks had to go through .

[longbed67]

For those who wont go look it up here is the jist of it....

K&N Filters get their increased air flow through increasing the micron filter size of the material and when you look on a lock box setup using a K&N vs even a standard paper or Foam Filter the K&N yes flows more, but on the same note also allows more dirt to flow through, to the point that after a couple of hours of testing one can visually see dirt building up in the box. My friends dad works for a company that independently tested just about every filter type imaginable for use in their machinery just to see what was going to best protect the machinery at their facility cost aside the k&n allow the most dirt to get in and the oiled foam protected the best. That said the oiled foam was also the most restrictive, but not by much.

The tornado thing in actual dyno tests not done by that company has shown to decrease HP and when looking at total cfm of flow through a pipe has shown huge restriction in the amount of air allowed to pass through the pipe in the same time under the same conditions, the whole disturb the air and funnel it down in faster is a scheme that is catchy and sounds good to the buyer but doesnt actually work in real life. It is kind of like the concept of a cool looking fishing lure that catch's the fishermans eye but would never catch a fish.

[bucktruck68]

Thanks to all for the info. Funny how one discussion branches off into other topics. Which is very good. I have several things to think about but I have a good idea of the direction to go. I have some time before it arrives here but never to early to start the process. I'll keep you posted and hopefully post pics when i get it going.

[WorkinLonghorn]

If your mileage is that crappy with Normal Driving you know, not racing every car off of every stop or light, but just putting around, then before you spend a penny try cupping your hand over the end of the exhaust pipe and see if it is a steady vibration with occasional bigger puffs or if there is a regular big pulse that may indicate a miss. If you find a miss then you can hook up a tach or just pay close attention as you remove and replace spark wires one at a time and determine which cylinder is not contributing (RPMs don't go down when that plug wire is disconnected).
Post here if this is the case. If you have or can borrow a compression tester then check and write down the compression for each cylinder with all the plugs removed and the throttle wide open, cranking with a reasonably good battery.post results here.

[RUSHNBOBO]

Optimize your ignition timing to the very edge of ping / no ping at every rpm and load situation, most older vehicles can run far more timing than they currently run. New computer controlled vehicles do all this automagically for every conceivable situation.

You can't do that, but get it right for the area you drive the most. Also run a adjustable vacuum canister and dial it in after the mechanical is set up right. Mileage ,power, and cooler running engine are just some of the benefits.

[oldblue1968chevy]

Whats your total timing/initial timing at? General tuneup would probably help as well

[stsalvage]

well i like these kinda story's.I feel the stock 355 30 over 350 would be a better daily driver.the 200R4 and the 700r4 1987--93 all cable transmissions.Not sure if it had AC if so put it back to factory last longer and the parts are all over the place In 1968 you could add a factory power steering box with power brakes.the disc brakes from 1971--87 will work.But your A Arms on your truck are serviceable with out a press so just buy stock or what ever disc brake set up and i think your drive shaft will need to be shortened rear end find one out of a 1964--70 with the 6 lug or 1971--87 for 5 lug

[kikkegek]

he man! I love these topics. I have spent one on my 86 K20 Suburban.

Not because I want to save fuel, but because I want it to run as good as it can.

http://67-72chevytrucks.com/vboard/s...d.php?t=429908

I have done lots of stuff,hoping for improvement in MPG:
- no-clutch fan to flex fan (no improvement)
- open airfilter under the hood to Cold Air Intake (no improvement)
- replaced bad sparkplug cables (no improvement)
- tuned timing, was at 0 BTDC and changed it to 10 BTDC (I run LPG)...(no improvement)
- rubbing rear brakes, changed the pads and cilinders (no improvement)
- correct tire pressure (no improvement)
- removed all linds of smogg junk (no improvement)
- had the LPG system tuned by a specialist (no improvement)
- changed the thermostat from 180F to 195F (engine wasnt warming up right, but no improvement)

The only thing that really made a noticiable difference in my case, was changing the flex fan to an electric fan. Not My highway MPGbut my city MPG went up from that. engine warms up quicker,because the flexfan would always pull in cold air when idleing...and you loose drag from the flexfan when changing to electric fan.

I am now at 8.7 - 9.0 mpg....

I tihnk the only thing for me left is:
- getting rid of the 4WD (used it once in 20.000 km for 2 minutes)...
- changing the rear gear ratio from 4.10 to lower gears...

I dont think my wife will let me take the 4WD out, since its her car and she like the idea that whenever we will have snow, she can use the 4WD.

[MARKDTN]

I am surprised nobody has said fuel injection swap. You can buy a 90s truck for cheap and pull the engine and OD trans. Either the TBI or Vortec can work. Mileage and power should increase. win-win. Very few mods required to the truck, especially with a Vortec, most of the wiring is in the engine compartment. Will need a FI fuel tank or pump and probably aftermarket wiring harness.