New Setup

[mississippibandit1]

Hey guys I have a 1972 C10 With the original 350/Th350 combo and I believe it has 3.08 gears in the rear. I have put a Edlebrock dual plane intake and a holley 600 carb on it. Im wanting to make it a great truck to go to the cruises in and currently the gas mileage is horrible, maybe like 8-10 mpg. I was wondering if you guys could give me some pointers as to which way I need to go eigther a complete drive train swap or what pointers you may have to make the current setup better. Thanks guys for all the time and effort yall put into this site ive enjoyed reading it many many years. P.s I put some photos of my ole gal.

[garyd1961]

A 350 trans and 3.08 gears should be ok on the road. Your gas mileage problem is most likely something to do with the motor. The original motors weren't known for great gas mileage, gas was cheap in 1972. You would need a more up to date motor or a rebuild with a more modern cam and heads, but the increase in gas mileage wouldn't be worth it unless you drive a lot of miles. Unless the motor needs replacing for some other reason I would just do a good tune up and keep driving.
BTW nice looking truck.

[mississippibandit1]

Thanks, I thought about doing a LS swap, but i also considered putting vortec heads and a 280 comp cam but im just not sure on the best route, id like to put her in a few shows when shes complete as well. I still got a long long way to go but if shes not running up to par I feel my efforts would be in vein on looks.

[krcotter]

You could try a tranny swap to a TH-200-4R (overdrive baby).

[Overdriven]

Obviously the more modern engines and parts are going to be more efficient, whether it's vortec heads or a LS swap. Maybe do a search and see if there's a MPG thread in the LS section. If the numbers are attractive enough to you maybe a LS swap will be worth it to you. You could also look up MPG numbers for late model LS pickups, just be aware the trans you choose will impact those numbers. The th200r4 is the same length as a th350 so you won't have to do anything to the driveshaft if you want overdrive but 3.08 is on the low side with overdrive.

But unless you have your heart set on spending $ for hardware changes tuning is going to be your best friend. Can you read plugs to determine optimal jetting? Do you know what each of the carb screws do exactly and can determine their best position? How about the ignition side of things? If not then maybe paying someone else more knowldgable could yield significant gains in performance and economy. Either way, until you know for sure your current combo is performing at its best it's hard to know what will offer the best improvement. If I had to take a semi educated guess I'd think your combo might be capable of about 12mpg highway (with the perfect cam) depending on cruising speed/rpm, add 1-2mpg with vortec heads. If you want better than that you'll have to start looking into OD trans/rear gears and/or LS swap.

[mud.man.rj]

Even if you get timing the best tune, maybe roller rockers and do all you can may only increase mpg by 2-3 at best, big heavy 2wd, a 4wd is worse yet. Do all you can or spend the difference and swap in an LS which is the best bet for long term mpg. A 4 spd auto won't make much difference unless you get up to 4th gear often which is more highway not around town.

[truckster]

With your setup that truck should be able to hit 13-14 MPG. I would check ignition timing first and then tune the carb. My 4wd Blazer was giving me 11-12 MPG on an old tired motor before it threw a rod.

[Coley]

...I would stop, take a minute and find out what I've got to start with.
By that I mean do a check/analysis of your engine and find out what kind of shape its in.
Give it a compression test for absolute starters. The higher and more even the numbers...the better your fuel mileage will be because your engine is running efficiently relative to its intended design and purpose.
If your compression numbers are down and uneven....you will not be able to pull up either power or fuel mileage.
(note: I would hope for numbers all at or above 130psi....ideally all in the 140-150 psi range. If they are down around 100-115 range, which is possible....you are probably getting close to needing to refresh it or replace it)
Start there.

all Good
Coley

[webfoot]

Vacuum secondary carb, especially a quadrajet, and timing. From that mileage I'd guess you have a double pumper which isn't going to win any mpg wars.
Posted via Mobile Device

[mud.man.rj]

Good point on the carb, best mileage would be a factory carb, small primarys make quite a difference compared to Edelbrock and especially a Holley.

[Lancialonnie]

I'm in the same boat with my 307, I'm getting only 8 mpg. I'm thinking of trying a fuel injection set up like FITech to see how much that helps. Fuel injection would be cheaper and easier for me than a new OD trans like a 700R4 which would probably give the biggest improvement in mileage. I'm saving up for the FI now, hopefully I can do the upgrade soon so I can drive my truck now that it looks nice.

[leftybass209]

I think you have a tuning and jetting issue with your current setup, and possibly some mechanical issues as well. A Quadrajet carb would be ideal for good gas mileage and good performance. There's sbc motors that make 350-400 hp and net equal fuel mileage to what you're getting currently.

A few words on fuel mileage though: switching to an overdrive trans, or an LS swap (unless they're given to you) for the sake of fuel mileage gains only, is a big waste of money. The costs of the swaps and the parts themselves would take thousands of miles of fuel and possibly years, just to break even on the cost.

[kashola]

Some good points made here. I agree with those that suggested a quadrajet (if you're staying with a carburetor) for fuel mileage. The small primaries are ideal for that. I also agree that an engine/tranny swap strictly for the sake of mileage is overkill. You'd likely never make up the difference, dollar-wise. One question I haven't seen answered is, how do you drive it? If you're trying to burn the tires off at every light, your mileage with suffer. Give it a good tune up, make a concerted effort to drive easy and you may be surprised.

[krcotter]

I agree with most everything posted here so far. Check the fundamentals first, engine timed and tuned properly first, then make sure the carb is properly tuned (I have the same issue right now with a rich Edelbrock, so I'm going in to a specialty carb shop tomorrow to have it set up properly).

Don't forget the other fundamentals, like tire pressure.

I live out in the country, and I get up to cruising speed frequently, so I have another goal to get a 200-4R overdrive tranny. I chose that tranny for 2 reasons, size-wise it's a direct bolt on with only the crossmember needing to be moved back to a different set of holes, and because it uses way less HP to operate compared to the 700-4R.

It should cut RPMs by almost 1/3 when down the country roads. I'm planning this swap for both MPG and to reduce RPMs and noise when going down the interstate. You have to determine what your needs are, and how you'll use your truck. Do your research and plan what's right for the way you plan to use your truck.

http://www.oldengine.org/unfaq/leadfoot/trans.htm

[GASoline71]

I've never bought one of these old trucks and worried about MPG. They had horrible MPG from the factory when new, and with the drag coefficient of a brick... gas mileage really isn't going to improve much.

Cats that claim near 15mpg either have a really light right foot, or some weird voodoo going on.

Gary

[mississippibandit1]

Guys I appreciate everything posted here and I am going to check on the engine and carburetor and make sure everything is set up right and running right, but I am also leaning tword doing a 2004R like KRCOTTER was talking about doing, I have researched it and I believe I am going to try that 2004R and see what kind of mileage I get with my stock motor. If that does not satisfy me I will look into doing either a LS1 or LS3 and from what I have seen a LS3 is more to my liking but before I do all that I am going to try this 2004R. Let me ask this if I do end up doing a engine swap do I need to do the brakes as well?

[leftybass209]

Originally Posted by mississippibandit1

Let me ask this if I do end up doing a engine swap do I need to do the brakes as well?

Need to? No

Should you? It's a safety item, and should realistically be done, or considered before anything else.

You already have stock disc/drum set up, what were you considering?

[cypressbog]

Originally Posted by leftybass209

A few words on fuel mileage though: switching to an overdrive trans, or an LS swap (unless they're given to you) for the sake of fuel mileage gains only, is a big waste of money. The costs of the swaps and the parts themselves would take thousands of miles of fuel and possibly years, just to break even on the cost.

I get a kick out of people that install a $1,000 fuel injection, LS swap, overdrive on their ride so they can get maybe 5-6 mpg better. By the time they break even, the motor is shot, lol

[bhayes1]

Originally Posted by cypressbog

I get a kick out of people that install a $1,000 fuel injection, LS swap, overdrive on their ride so they can get maybe 5-6 mpg better. By the time they break even, the motor is shot, lol

Cypressbog, not sure that I agree with your logic.


I think one of the main reason people do an LS upgrade is because their current set up is tired and likely needing a rebuild anyway. Lets say you spend 2k on a basic carburetor crate engine set up and another 500 bucks freshening up the tranny. This puts you at a total of $2500.00

On the other hand lets say you source an LS engine and tranny for 2k and spend another 2k on misc. parts for the conversion including the tank, fuel pump, motor mounts, harness etc.

This puts you at a difference of $1500 bucks. If you drive 15,000 miles annually @ 11 MPGs (carbureted) and gas is $3 per gallon (California pricing) / 11 MPG =. 27 cents per mile x 15,000 miles = $4050 annually in fuel. If you drive 15,000 miles annually @ 19 MPGs (fuel injected) this cost you: $3 per gallon / 19 MPG =. 16 cents per mile x 15,000 miles = $2400 annually in fuel. For a total difference of $1650.00 (enough to cover the difference in the swap in just 1 year.

Okay maybe you only drive half that a year, then it takes you 2 years to get a return on your investment. It all depends on what you prefer and how much you drive. I see LS motors go for 200k plus routinely. For owners who drive their truck frequently and aren’t worried about originality then you are money ahead to do the swap.

[krcotter]

Isn’t the LS motor a really high performance motor. I thought I read one of the big advancements was a much larger physical cam in relation to standard camshafts, and that allowed smoother lifter rotation? I’d love to stuff a more modern motor in my truck, like a Vortec 5.3. I don’t think the better mileage would be a primary consideration, RELIABILITY would. In fact that might also be the reason to stay away from the brand new EcoTec motors.

I’m really a fan of modern fuel injected motors. Having a fuel injector computer recalculate fuel/air constantly results in virtually no carbon buildup also. Kids today don’t even know what a choke is, let alone about the strive for ideal fuel/air mixture. Modern motors have tighter tolerances. We should all be using synthetic or semi-synthetic oil in these engines, so we get better lubrication and no sludge buildup. This is why newer cars run for 250/300K with proper maintenance. Many of our parents felt the life of a vehicle was only about 100K growing up (I'm an old GenXer).

Unfortunately my old c10 would need a lot of other upgrades, like brakes if I were to put a Vortec in her. My primary ride is a 2005 Honda Element, and the idea that I can still just put the key in and it will start no matter how cold or hot it is and will run great warms my heart a little. I’d love to upgrade my Element to a brand new 2500 HD for the same reasons as above. I’d like to upgrade my snowmobile to a fuel injected model as well reliability.

The primary reason to upgrade to a Vortec or LS engine should either be reliability or to race respectively. So, forget about all of those calculations and determine how much you want to drive your truck, and how often you want to be working and tuning the engine/timing/carburetor.