First thread how about aerodynamics on our trucks?

[Astro-Balls]

Remove the front and rear windows, wear goggles...

[Steeveedee]

Originally Posted by Cms83

I do plan to haul stuff with the truck. I got 2 1/2 acres here south jersey. So plenty of need for hauling. Just can’t haul much until I fix the bed. It’s pretty rough. Do you think that 3.07 would allow for decent hauling? With out it being a dog? Let’s face it 305s are good engines. But not much power out of them. I think my truck originally had a 307. I believe they used the heads, carb and intake from the original engine. I don’t recall the heads cfm. I think it is around 62 64 66 maybe. I am sure I got high compression because of the heads. If I am wrong about that don’t be afraid to school me. I say that about the 307 because that’s what the carb was from. So I’ve been told

I doubt that the 3.07 would be a good hauling axle ratio. I only offered up that ratio as an example of how much you could reduce engine spinning. You need to consider more input from the people here before making the decision on a ratio that will work best for you. I have a 3.54 axle in my truck and get 7 MPG towing a 6000 pound travel trailer. I wouldn't trade off any of my setup, as it is made for towing a trailer. Do you expect to only fill the bed, or haul a trailer, and how much in each case (or maybe the bed full and a trailer)? I think that if the gear ratio you posted is correct (it seems awfully steep) that some gains could be made with a lower numerical ratio. But that's going to be some money if you can't do the work yourself. Given the distance you drive, you might recover you costs quickly, but that's not for me to say.

[cornerstone]

I’ll be the one to take the heat here. Unless you NEED to drive your classic as a daily, why are you? If you work 5 days a week and spend 25 a day for gas, that’s 500$ a month! How about get a gas miser? I love my Chevy trucks as much as the rest of y’all here, but you could afford a car payment and pay for the gas to drive it instead of putting the miles on old faithful! Obviously your call but felt like it needed to be said.
Brian

[RustyPile]

Originally Posted by cornerstone

I’ll be the one to take the heat here. Unless you NEED to drive your classic as a daily, why are you? If you work 5 days a week and spend 25 a day for gas, that’s 500$ a month! How about get a gas miser? I love my Chevy trucks as much as the rest of y’all here, but you could afford a car payment and pay for the gas to drive it instead of putting the miles on old faithful! Obviously your call but felt like it needed to be said.
Brian

I'm sure glad somebody finally had the balls to say that.. I've been following this thread very closely, and have been trying to get up enough nerve to make your exact statement.. I consider my '71 a daily driver, (see my avatar) but the combined age of my truck and myself is 124 years.. At that age, our daily drives are few and far between.. I think the rear-end ratio is 3.73 (the truck originally had an I6/tott), and could be something lower.. I never haul anything heavier than a few junk yard parts picks.. My usual passenger is my 20 lb Mini-heeler.. We both love the song produced by my built 454 BBC's glass packed 3 1/2 inch pipes going 55 mph.. Gas mileage is terrible (I'm ashamed to state the #s), but I DON'T CARE. I wouldn't change a thing on it. As you said, "It's a classic not intended for long daily runs".. If you want better gas mileage, get a gas miser and make the payments with the money saved on gas..

Originally Posted by RustyPile

I'm sure glad somebody finally had the balls to say that.. I've been following this thread very closely, and have been trying to get up enough nerve to make your exact statement.. I consider my '71 a daily driver, (see my avatar) but the combined age of my truck and myself is 124 years.. At that age, our daily drives are few and far between.. I think the rear-end ratio is 3.73 (the truck originally had an I6/tott), and could be something lower.. I never haul anything heavier than a few junk yard parts picks.. My usual passenger is my 20 lb Mini-heeler.. We both love the song produced by my built 454 BBC's glass packed 3 1/2 inch pipes going 55 mph.. Gas mileage is terrible (I'm ashamed to state the #s), but I DON'T CARE. I wouldn't change a thing on it. As you said, "It's a classic not intended for long daily runs".. If you want better gas mileage, get a gas miser and make the payments with the money saved on gas..

Agree. To each his own but even here in CA (where gas is $1 more than anywhere else in the US), gas mileage is not my concern. These are trucks. Heck, I consider my K10 a dramatic improvement over my 69’ FJ40 which basically has a tractor engine. In short, they were never meant to be gas misers; just like Harley’s were never meant to outspeed (or out handle) any number of other “refined” other bikes but they are way cooler— just like our trucks. People give you the thumbs up on your ride—my guess is is no one ever said— “so, how’s the gas mileage on that baby”

[Ironangel]

You can tune a piano, but you cant play a "brick"...~Ghostrider~

[rpmerf]

Agree about the rear ratio OR the trans OR both

RPM @ 55 MPH with a 1:1 trans ratio
4.56 = 2,657 RPM
4.11 = 2,395 RPM
3.73 = 2,173 RPM
3.54 = 2,063 RPM
3.27 = 1,905 RPM
3.07 = 1,789 RPM

RPM @ 55 MPH with a 0.70:1 trans ratio (OD)
4.56 = 1,860 RPM
4.11 = 1,676 RPM
3.73 = 1,521 RPM
3.54 = 1,444 RPM
3.27 = 1,334 RPM
3.07 = 1,252 RPM

Personally, I would go for an overdrive transmission over a rear end swap. That way you get to keep the high torque, but still have the low RPM on the highway. You will want a lockup torque converter to drop the RPM as low as possible, and not risk burning up running at too low of an RPM for too long.

You might be able to look into an overdrive unit that bolts onto the back of your trans. You will need to shorten your driveshaft.

Edelbrock Performer intake is still good. I've been looking at the 2101. I like that it has provisions for a divorced choke, quadrajet, and no EGR.

Good air fuel is crucial to good gas mileage. At cruise, you want to be around 16.0:1 - 17.0:1. Where ever your engine is happy and doesn't surge.

Quadrajet tuning: http://www.capitalcorvetteclub.ca/at...ng%20Paper.pdf

Check over your ignition system. Be sure the contacts are clean. Make sure your coil is putting out a good spark. Check your plugs. Make sure your timing is good. If you have points, check the dwell. Might consider upgrading to HEI. Initial timing doesn't matter too much. Should be about 34-36* from the mechanical advance. It should be all in around 2500 RPM. Should about about 10-12 from the vacuum advance. You want to be sure it doesn't ping when cold (choke on).

If your radiator fan is directly bolted to the water pump, a clutch fan will allow it to draw less power. Electric fan is even better.

On the topic of aerodynamics. I've heard of people getting gains from making belly pans of different vehicles. I think you would have to lower the truck significantly to really see an MPG improvement.

According to google maps, your driving about 85 miles a day. You said about $20-30 a day. I'll guess around $3 / gal. This would be around 6.67-10 gallons. This gives us between 8.5 MPG and 12.7 MPG. At an average of $25 a day, that's $125/week and at 50 weeks a year, that's $6,250.

If you can find a beater that can get about 25 mpg and cost less than $3k, it should pay for itself in a year. You can do the math on how much it costs to buy, repairs, gas, and insurance over the year vs just driving your truck.

[jkeady]

Originally Posted by cornerstone

I’ll be the one to take the heat here. Unless you NEED to drive your classic as a daily, why are you? If you work 5 days a week and spend 25 a day for gas, that’s 500$ a month! How about get a gas miser? I love my Chevy trucks as much as the rest of y’all here, but you could afford a car payment and pay for the gas to drive it instead of putting the miles on old faithful! Obviously your call but felt like it needed to be said.
Brian

I started writing something similar but didn’t have time to finish.

These threads pop up a lot. The question usually is along the lines of, “How can I make this thing an economical daily driver” and the answer really amounts to: you can’t. Granted, “economical” is relative to the individual, but no one to my knowledge has a recipe for getting a SBC in one of these rigs up to the mid-20 mpg range.

It’s of course a good idea to try to keep your truck tuned up well and if you aren’t after max performance you could even run it a little on the lean side. But my thinking is: if you even have to ask about how to get better mileage, maybe this is not the daily driver for you. I daily a ‘97 Escort wagon which is a bland little econobox that gets a consistent 30 mpg on my 60 mile daily round trip. I usually take the truck to work a few times a month for fun. Not only does it save gas but it saves wear and tear on my truck (which is, incidentally, my only truck and I use it as one). I was pretty happy to find the ol gal getting a consistent 9 mpg on our first camping trip this year.

[Barnfind46]

Mine gets about 12-13 mpg with a 350/350 and 3.73 gears. I'm good with that. It is a brick and I don't drive it every day, but I get more smiles per gallon than anything else I drive!

[HO455]

You might look into the Ranger overdrive from Advance Adapters.


https://www.advanceadapters.com/prod...etainer-index/

[RichardJ]

If you're going to drive a brick at 55 mph, aerodynamics has little to do with the conversation or at the very most, a very minimal effect.
Power required to overcome air resistance increases exponentially with speed.
I.E., the difference in power to get from 20 mph to 30 mph could be 2 HP. The additional power needed to get from 190 mph to 200 mph could be an additional 200 HP.
Aerodynamic modifications that will help a vehicle at 100 or even 80 mph will have zero or minimal effect at 55 mph.

In this chart, this particular vehicle needs 100 HP to travel at 55 mph. but at 75 mph, it needs 250 HP.

These old trucks were designed to carry loads from point A to B. They used low rear gears to get the load moving from a stop and keep it moving on hills.

You want to cruise at 55 and get better fuel mileage, loose the low gears.

A better transmission will aid in providing better mid-range gear selection and help with fuel mileage. It will even help you haul a barn or whatever load you had in mind.

You want to keep an ancient 3-sp trans, but you are willing to make outlandish body modifications to help with some perceived aerodynamic gains. You're not making sense.

[Cms83]

Well the thing is I don’t plan for it to be my daily driver for ever. I was wondering if any changes other then mechanical would be worth it just under the reason of it helping in mpg. It’s just right now, this is what I have as a daily driver for now. Even when it isn’t a daily driver I still want to get the best mpg’s. I figured changing the gear ratio and over drive would help that is obvious. There’s been some unfortunate things that have happened in the past year or so. That has made this truck my daily driver. I am not going to sell it and buy something better In Fuel mileage so this is what I have. I can’t get anything else right now other then selling the c20. In fact I had a s10 that got wrecked and my 09 Chevy traverses engine done locked up. I took this job when the s10 was running.

[Cms83]

I also herd those OD units aren’t that much of jump in gear ratio. I just don’t now anyone that got one. I also have a 700r4 trans that has to be rebuilt. Just I got to fix the family car before anything on me truck

[Cms83]

You want to keep an ancient 3-sp trans, but you are willing to make outlandish body modifications to help with some perceived aerodynamic gains. You're not making sense.

[/QUOTE]

I don’t think a front spoiler and lowering it would be “outlandish “ body mods. The only thing that I mentioned was a headache rack or bulkhead being in place behind the cab would help or a bed cap. Thank you for the graph though

[67swb72klb]

I would stay with a stick shift o/d trans and soften up the rear gear

[toolboxchev]

Originally Posted by Jonny Hotnuts

I have vested a significant amount of effort in learning the evil ways of aeros (landspeed racing on the Bonneville Salt Flats).


You have 2 issues with these trucks. Fa (frontal area) and Cd (coefficient of drag).
These combined give you your CdA (drag x Fa).

The C10 has a LARGE Fa. You can gain a decent improvement on Fa and Cd by lowering (note the Cd is improved due to lowering by limiting the amount of dirty air under the vehicle). You can get a noted improvement on MPG by lowering.....but it wont be life altering.


This is because......


Most of the aero drag is generated in the aft sections (behind cab, behind tailgate). The stark drop off behind the cab generates a large low pressure area and this MURDERS the Cd.


If you wanted to make the truck more efficient you will need to find a way to decrease the low pressure area behind the cab. You 'could' chop the top (this will also lower the Fa as well) or put a slight rake in the roof (lower in the back of the cab). You could also install some sort of NASA ducts in the side of the bed to take air from the sides of the truck and 'fill' the low pressure area of the bed OR cut some venting in the bed floor so the higher pressure under the vehicle would help equalize the lower pressure in the bed.


All this being said.....

its a truck, its a brick. It can be made better but the cost of aero improvements is very high.


good luck.

~JH

I always drop the tailgate and put a tool box behind the cab.

[special-K]

Originally Posted by cornerstone

I’ll be the one to take the heat here. Unless you NEED to drive your classic as a daily, why are you? If you work 5 days a week and spend 25 a day for gas, that’s 500$ a month! How about get a gas miser? I love my Chevy trucks as much as the rest of y’all here, but you could afford a car payment and pay for the gas to drive it instead of putting the miles on old faithful! Obviously your call but felt like it needed to be said.
Brian

My answer would be, "Yes, I do have to". I would love to own a gas miser. But even if I could afford another vehicle, insurance policy, registration, more maintenance, and repair costs it couldn't do the job I need my daily driver to do. If I only have one vehicle it has to be a 3/4t truck because I am a housing contractor who needs to haul tools and materials and haul a trailer... the reason trucks exist.

I only use my '72 K2500 three seasons due to salted roads, but my true daily driver is a far more aerodynamic with fuel injection and overdrive '95 K2500 that gets the same mileage as the '72.

I saw "Aerodynamics on our trucks" in the title and thought this was going to be a joke thread and started chuckling before I clicked to open it up.

I truly don't understand, with the great strides made in fuel economy and lower emissions in cars we have made, why people choose to drive big heavy gas guzzling trucks in place of cars to the extent that car makers are dropping their car lines. Just plain ignorant? Desperate need to find a little macho identity or other complex? My neighbor retired and moved away. But he could never have retired if he did that. He worked 4 10hr shifts and had to drive over 50 miles one way to work. He drove throw away cars (he called them), then finally bought a new Chevy (smaller than Cobalt) for his last years of commuting. Just a common blue collar worker who couldn't afford anything new and more expensive if he wanted to do anything else other than make payments. But as it was, he spent his whole life building old Harleys, street rods, and old Chevy Trucks one after the other. A;ways had a bike and a cool ride for his three days a week off work... playing in the shop when he wasn't running one. These people with way more dollars than him must have a whole lot less sense. A good ole boy knows how to make what he has work for him. That's what Eddie did.

[Jonny Hotnuts]

Originally Posted by toolboxchev

I always drop the tailgate and put a tool box behind the cab.

Imagine this:


You have a low pressure area behind the cab.
You have a high pressure area in front of the tailgate.


You loose the high pressure area when the tailgate is down.
Tailgate up, the high pressure area in front of the gate actually bleeds forward low in the bed and help equalize the low pressure behind the cab.

To see an example (without a wind tunnel).
Suspend a ball a few inches above the bed floor in the middle with surgical rubber.
Drive at speed. The ball will actually pull forward. This is because of the high pressure from the tailgate bleeding forward.



Its basically wash from an aero perspective. You gain some by getting rid of the low pressure area behind the tailgate but loose because the back of the cab has increased low pressure with the gate down.


~JH



Check out this aero nightmare! My 'fatter' self (down about 50lbs) and crew chief a few years ago. All the aero research was done at the Daimler facility here in Portland (I had a small hand in this one).

-wonder what sort of mpg this guy is getting with 16 cylinders! LOL




~JH

[special-K]

Lowering the tailgate might help with reducing drag, help the exit aerodynamics, but it won't help gas mileage. Heck, I run ladder racks loaded with ladders, 20-30' walk boards, and 24' pump jack poles and that doesn't affect the mileage either. Neither do visors

Originally Posted by special-K

My answer would be, "Yes, I do have to". I would love to own a gas miser. But even if I could afford another vehicle, insurance policy, registration, more maintenance, and repair costs it couldn't do the job I need my daily driver to do. If I only have one vehicle it has to be a 3/4t truck because I am a housing contractor who needs to haul tools and materials and haul a trailer... the reason trucks exist.

I only use my '72 K2500 three seasons due to salted roads, but my true daily driver is a far more aerodynamic with fuel injection and overdrive '95 K2500 that gets the same mileage as the '72.

I saw "Aerodynamics on our trucks" in the title and thought this was going to be a joke thread and started chuckling before I clicked to open it up.

I truly don't understand, with the great strides made in fuel economy and lower emissions in cars we have made, why people choose to drive big heavy gas guzzling trucks in place of cars to the extent that car makers are dropping their car lines. Just plain ignorant? Desperate need to find a little macho identity or other complex? My neighbor retired and moved away. But he could never have retired if he did that. He worked 4 10hr shifts and had to drive over 50 miles one way to work. He drove throw away cars (he called them), then finally bought a new Chevy (smaller than Cobalt) for his last years of commuting. Just a common blue collar worker who couldn't afford anything new and more expensive if he wanted to do anything else other than make payments. But as it was, he spent his whole life building old Harleys, street rods, and old Chevy Trucks one after the other. A;ways had a bike and a cool ride for his three days a week off work... playing in the shop when he wasn't running one. These people with way more dollars than him must have a whole lot less sense. A good ole boy knows how to make what he has work for him. That's what Eddie did.

Tim, that was very close to poetic--good thoughts and commentary as usual!

[special-K]

Thanks. Things don't always come across so clear for me. Might have to do with being fresh back from a long weekend in the mountains and a whole lot of good conversation with my very philosophical and clear minded 89 year old mom. That and being in the place of my roots is good therapy.

[C4UC101969]

I have an all stock 307 with a three on a tree 4 barrel carb, with 20"x9" wheels. Before when I used to run on octane 87 which here in Canada has 10% ethanol in it, I got solid 10 mpg driving on country roads and never past 55mph, now the moment I switched over to 91 octane which here in Canada has no ethanol my mpg went up to a solid 14-15mpg. I know that premium gas is more expensive but I would imagine that getting 40% more on your mpg is worth the extra cents it costs for premium gas, that is just my thought on ethanol in gas. Try that next time and maybe you will also see a significant difference(i am sure your state's regular gas is 10% ethanol or more).....as to aerodynamics on these trucks and increasing mpg something that does not exist in my opinion.

[Steeveedee]

Originally Posted by C4UC101969

I have an all stock 307 with a three on a tree 4 barrel carb, with 20"x9" wheels. Before when I used to run on octane 87 which here in Canada has 10% ethanol in it, I got solid 10 mpg driving on country roads and never past 55mph, now the moment I switched over to 91 octane which here in Canada has no ethanol my mpg went up to a solid 14-15mpg. I know that premium gas is more expensive but I would imagine that getting 40% more on your mpg is worth the extra cents it costs for premium gas, that is just my thought on ethanol in gas. Try that next time and maybe you will also see a significant difference(i am sure your state's regular gas is 10% ethanol or more).....as to aerodynamics on these trucks and increasing mpg something that does not exist in my opinion.

You could probably pull your base timing up a bit and/or adjust the centrifugal advance for all-in timing earlier with the premium fuel and gain enough to pay for an advance spring and weight kit. In fact, if you haven't done this, I'd put money on it. I can't do that around here in California, though.

It has been noted that in general, premium fuel provides no benefit. This is so if no timing or carburetion changes are made.

[special-K]

The fact that your premium has no ethanol is why your mileage is better. This great thing called ethanol that cuts back on 10% of petroleum product makes a vehicle use that much more fuel. Ironic for sure.

The 307 is the small block for best fuel economy and longest life. I had a 307 I built for power and hiway economy in a '71 K/20 with 4.57 gears and 37/14.50 tires. It got 13-14 mpg hauling the siding I installed, tools in the side boxes, and scaffold on the ladder racks. I put an RV cam in, 1.94" 64cc heads, factory 4bbl manifold with Holley 450cfm spread bore, Melling high volume pump, and HEI w/weight & spring kit. Also full-length headers and 2 1/4" pipes through turbo mufflers. Ran great snf when cruising along on primaries it sipped fuel. I was never too easy on it light to light and around town either