20 plus mpg question

[jesseo]

I am just getting started on my 66 sb stepper build. Plan is to do air bags, no notch, drop spindles in the front. 283 with either 4l60 or 700R4 and thinking of 3:73 rear end.

My goal is to have a good daily driver that gets 20 plus mpg on the frwy and can tow a small travel trailer on occasion.

Am I on the right track here or living a pipe dream?

[tincan1966]

Our '65 daily driver has a 305 Throttle body injected motor with a TH350C lockup trans and a 3.08 rear gear, 28" tall rear tires.

Normal driving, it yields an average of 18.5-19.5 mpg.

20 mpg or even more is obtainable and very doable-just may take some tinkering and adjusting to get there. Not sure if you can get there with a carb, as I am more of a EFI person. But I bet someone can.

[61_FL_Apache]

Good luck with that.. My 305/TH350 3.08 and 28" tires gives me 12-13mpg. I would love to get 20. When you figure out the secret, please share with the class!

[TJ's Chevy]

Fuel injection with headers and an hei will give you better milage. Plus a 6 speed would help or a turbo 400 with a gear vendor over drive would really help. My buck and a half.

[Wolfinthesnow]

Just my .02 cents. I think it's very doable, especially with the over drive transmission. I would suggest however a higher ratio. I don't feel that it's impossible with a carb either, just as long as its tuned correctly. Good luck with your project and pics would be awesome!
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[tincan1966]

The setup we are running came out of a 1991 Olds Custom Cruiser wagon(full sized) 4100 lb car. It had a 700R4 trans and a 3.42 gear, got 20-22 mpg all day long. truck is similar in weight, but has 3.08 gear. 700R was bad so used the TH350C with lock up converter that I had. Final drive is not really overdrive, it merely takes out all the slip in the converter, still 1:1 final, but engine RPM drops below 2000.

I also forgot, we changed out the tires to a set of 20's w/ 245/75/R20 that are actually closer to 30" tall, so that attributes to a higher effective ration, as well.

[Clyde65]

I have a 4.8, 4l60e, 3.73, 28" tire, lowered. 4/4 and when I get all hwy, without a strong south wind, I have gotten 20.5mpg, consistent 19 tho. I baby it and don't hot rod. I too pull a smal travel trailer but I probably drop to 14-15 hwy with the small box I'm dragging.
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[LVPhotos]

I got up to 25 MPG with a tired 283 and 5 speed .67od and 3.73 28inch tires.Edlebrock 650 manual choke. Its how you drive. Better MPG with a stick. Your automatic will still have a load on engine when stopped.
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[gimmy 64]

I don't see 20mpg without going to a lsx swap. I have a slight built 350 with a 2004r tranny 3:54 gears and it was built for my gears and tire height. I get around 14 on the freeway. that's not to say you can't do better but I don't think it will happen. 20 is a long shot.

[gimmy 64]

oh and that was doing 72 miles an hour at 2100 rpms. I guess if you wanted to drive 55 you could get better but here in cali you would get ran over lol

[jesseo]

Originally Posted by gimmy 64

oh and that was doing 72 miles an hour at 2100 rpms. I guess if you wanted to drive 55 you could get better but here in cali you would get ran over lol

I am sticking with the 283 for this reason. I know it still may be a long shot with the 283 but with a 350 I won't stand a chance.
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[Clyde65]

If you drive 90% hwy, then it is close to do-able iMO.

put a 2004r behind the 283, tune it right, then get maybe some 3.42 gears. that should get you close, if not, you could always throw an EFI on the SB.

Good luck however you choose, we all will be tuned in for sure!

[scottofksu]

I've been giving this some consideration as well... A recent option that has intrigued me is the new entry level V6 engine for the 2012+ Camaro...

Camaro Specs
Weight: 3,780 lbs
Drag: .37 CD
Engine: 3.6L V6
Output: 323 HP (6800 RPM)/278 TQ (4800 RPM)
Trans: 6 Speed Manual
Mileage: 17/28

1965 C-10 Specs
Weight: 3,220 lbs
Drag: .60 CD (Estimate from an average of full size trucks)

Granted, our trucks may be the least "slippery" vehicles on the road as far as drag is concerned, but they are also slightly lighter than the Camaro... Just some food for thought!

[jesseo]

Originally Posted by scottofksu

I've been giving this some consideration as well... A recent option that has intrigued me is the new entry level V6 engine for the 2012+ Camaro...

Camaro Specs
Weight: 3,780 lbs
Drag: .37 CD
Engine: 3.6L V6
Output: 323 HP (6800 RPM)/278 TQ (4800 RPM)
Trans: 6 Speed Manual
Mileage: 17/28

1965 C-10 Specs
Weight: 3,220 lbs
Drag: .60 CD (Estimate from an average of full size trucks)

Granted, our trucks may be the least "slippery" vehicles on the road as far as drag is concerned, but they are also slightly lighter than the Camaro... Just some food for thought!

Our admin gal has one with the V6. She went to Portland, OR (5 hrs on the frwy) and got 31 mpg. I have seen her get on it too and that thing will scream if you want it too. Best of all worlds with that engine. She has the auto trans too.

[ob1monkey]

I get a consistent 15 combined. 350 with a lump cam and a 600 edelbrock(desktop dyno said around 360hp/420tq) and a t-5 .7 overdrive. 3.08 LSD and 26in tire, I plan to do some carb tuning soon and hope to get closer to the 18mpg range. hopefully.

[theastronaut]

My sister has an '06 Trailblazer SS with a 6.0 LS2, 4l60E, and 4.10 gears. I drove it on the interstate this weekend and it got 17.0 mpg running 80 mph at about 2500 rpm with the cruise control on. This was up and down hills (driving in the foothills/upstate SC), four people in the car, and it weighs about 4300 pound empty. It will get 19-20 mpg on flat ground at 65 mpg.

I think a lighter truck, geared better, with any engine that's tuned properly can do better than that. The right amount of timing and getting the air/fuel ratio set in the right spot will have the biggest gains in picking up mpg.

I have a '64 VW bug that had a stock 1600 with a single barrel carb. It averaged 24 mpg driving back and forth to Greenville Tech daily, 100 mile round trip. I added 2 two-barrel carbs that flow 840 cfm, a header, and ratio rockers, and recorded a best of 36.25 mpg. That car has a 4.37 ring and pinion and relatively short 25" tall tires that don't help with mileage- it's all in how it's tuned and having a good combination of parts that work well together.

[theastronaut]

A wideband air/fuel gauge will be your biggest help in tuning the carbs for best mpg. 16-17:1 will yeild the best mileage. Tune the carb to run that lean when cruising, and 12.5-12.75 under load/WOT. You will need extra ignition advance added in only when cruising at lean mixtures since lean mixtures burn slower.

Innovate Motorsports MTX-L is one of the best out there.

[ob1monkey]

Thats what I purchased, I have tunned one car(the owner won't fill the tank so I can get numbers). and am awaiting my trucks return to the road so I can tune it. great tool for the money. the car I tunned suprised the owner once I was finished, and he has had the same setup for 5yrs or more.

[T Smith]

You have to remember, regardless of weight, gears, EFI, etc, these trucks have the aerodynamics of a brick.

[gimmy 64]

and also all of these new cars are computer controlled. so timing and air flow, fuel is constantly changing as you drive.

[jesseo]

Originally Posted by theastronaut

A wideband air/fuel gauge will be your biggest help in tuning the carbs for best mpg. 16-17:1 will yeild the best mileage. Tune the carb to run that lean when cruising, and 12.5-12.75 under load/WOT. You will need extra ignition advance added in only when cruising at lean mixtures since lean mixtures burn slower.

Innovate Motorsports MTX-L is one of the best out there.

Thanks I will be getting one of these for sure. I know a little but am learning a lo on here and from listening to the "old timers" who have worked on cars for year. I know I can get close at least. Hmmm this makes me think a fine tuned four barrel might be better than my little two barrel pushing so hard.

[jesseo]

I know I saw a review of an original car review of the 60 something chevy C10 and one of the lines being about it getting 20 mpg no matter how they drove it with a straight six.

[Chevysdominate]

I'd be willing to bet that the drag of our trucks is much greater then a modern truck by a good amount. Our trucks have 3-4 times the frontal area then any truck made in the last few decades. Just take a look at the front air damn we have. I also recently weighed my 1965 short wide at just over 3800 lbs with out me in it(+240 lbs). I think 3200 lbs is a little optimistic. Id be interested too know what others weigh in at.

With that said I have a stock 5.3 lm7, 4l60e auto, 3.23 gears and 28.1 inch tall tires and get not better then 19 mpg. I have cruise control installed as well. Add a manual trans and I think i would see 20+ mpg. Its very achievable but you got to work to get it.

Good luck

Originally Posted by scottofksu

I've been giving this some consideration as well... A recent option that has intrigued me is the new entry level V6 engine for the 2012+ Camaro...

Camaro Specs
Weight: 3,780 lbs
Drag: .37 CD
Engine: 3.6L V6
Output: 323 HP (6800 RPM)/278 TQ (4800 RPM)
Trans: 6 Speed Manual
Mileage: 17/28

1965 C-10 Specs
Weight: 3,220 lbs
Drag: .60 CD (Estimate from an average of full size trucks)

Granted, our trucks may be the least "slippery" vehicles on the road as far as drag is concerned, but they are also slightly lighter than the Camaro... Just some food for thought!

[Captainfab]

In building for max mpg's, I would go with a small block that produces more torque than a 283, since torque is what it takes to get these heavy trucks moving. The 283's are more of a high rpm engine instead of a torque engine. I would go with either a 305 or a 307. Built right and coupled to an OD trans and the right gears, I do believe that 20+ mpg's is possible.

[likaroc13]

Originally Posted by Captainfab

In building for max mpg's, I would go with a small block that produces more torque than a 283, since torque is what it takes to get these heavy trucks moving. The 283's are more of a high rpm engine instead of a torque engine. I would go with either a 305 or a 307. Built right and coupled to an OD trans and the right gears, I do believe that 20+ mpg's is possible.

Interesting that you mention that, because it reminded me of the '66 short/fleet my dad sold last year. It had a 307 with built TCI 700r4, & I think 3.73 gears. Not sure of tire sizes, but I know it had a staggered setup with street slicks in the back. It had a 5.5 front drop & the rear was a coilover setup. It was said that it would get up to 23mpg, but my dad never kept it long enough to confirm that.