Is it possible to build a big block for great performance and good economy?

[33 IMP]

Swap in a four valve cummins with 75 lbs boost, and an eight speed trans?

 

[Dodge Bros]

When curiousyellow71 drove the 510 to the track for the first time there was 7 of us that went down in a pack of cars to race/show. I remember joking that there to much distance to make it gas station to gas station on the interstate and he needed to carry a gas jug (he did carry one lol). First stop at a gas station he put less gas in than any of the cars, even the slant 6 car. He race Pro and made it to the finals, loosing in the final round from terrible traction in his lane. With all the rounds of racing it averaged just under 18 mpg when he got home.

I have often wondered what aluminum heads on that combo would have done.

 

[Challenger340]

I am going to check my Charger R/T SE's mileage next chance I get.... maybe even this weekend as time permits ?
Because honestly it just doesn't seem that bad at all with the 3.23 cogs ?
albeit,
a guy has to stay 60 mph which isn't all that feasible these days ?

It's an original un-rebuilt never touched #'s matching 1969 440 Magnum.... and I dunno if it meets the OP's 'performance' criterion ? but it can still roast both balonies(sure grip) easily out of the hole and squacks into 2nd on the auto all by itself.

 

[jeepthrills01]

I was able to pull 19 out of 69 RR 6-pak 4speed with 3.23s...all flat highway with a 26" tire back in 91....all it took was empty pockets of a teenager and the proverbial "egg" between my foot and the skinny pedal. That was commuting from Eastern Long Island to the Bronx daily.

 

[andyf]

Can a big block be built to make good power and still have exceptional fuel economy? I am just wondering if it can be done? What would it take?

Something like this.

 

[Nate S]

Typical 413-440 with late 60’s magnum cam, manifolds, maybe the stock AVS usually did around 13-14 for me. That’s averaged over maybe 4 cars, usually with a 3.23:1. 3 with 4-speeds, 1 with auto. On the highway at 65 they seemed to do the same. I remember a 383-4bbl in a ‘67 charger doing 17-18 on long highway drives.

A previous poster noted spinning the engine less. A huge difference, especially if it’s done with overdrive. I don’t know what’s really different but the newer cars seem to spin the engines freely, I’ll forget to shift my pickup into 5th or 6th and it doesn’t change much. Leave a 440 in 3rd and you’ll really notice it.

pay attention to:
Lower RPM
Lighter oils (engine, tranny, axle)
Proper vacuum advance - very important
Proper mech advance
Electronic ignition
Higher thermostat = higher efficiency
Higher compression - fuel may cost more than savings
Manual better than auto
Headers and good exhaust
Better than factory dual plane
Radial tires that aren’t too wide. Bias ply eats gas.
Proper alignment
Carb tuning - stock - light tan plugs
Smallest accelerator pump/shooter that works
Better boosters in carb, annular > Down leg > regular
Don’t block heat risers
Stay moderate with cam
Lighter wheels
Keep car light

 

[rumblefish360]

Can a big block be built to make good power and still have exceptional fuel economy? I am just wondering if it can be done? What would it take?

A stock or super mild build, add centrifugal supercharger and a OD, use a light foot and get good mileage. Use of a bigger cam kills mileage, so, use Rhodes lifters and cheat....

 

[Demonic]

A good bit of gas milage is how you drive it. I had a 71 Fury Custom Suburban wagon years ago. It got 18 mpg on the highway with it's original 383 2bbl and 2.76 gears.

 

[rumblefish360]

Personally, I think a lot is possible but like anything it depends on your goals. If you are wanting to get 30 mph out of one, well I don't think that will happen, they are too inefficient. However, 20 mph is possible I think but it takes some work. with modern technology such as good heads (aluminum) EFI and a system to control spark and fuel along with the right trans and rear gears as well as tires.

That there is key, part of it all. Take a good look at modern engines. Superior EFI w/ignition management, excellent induction (most engines) and excellent heads like the modern HEMI & LS engines, overdrive transmissions should NOT be over looked.

In all honesty, I don’t think we can match and compete with a modern engine but I do think we can get close. Close enough to raise an eyebrow or two.

In short, I believe building a dedicated turbo engine (not for insane power) is the answer.

Read your reply after I made mine. But I agree. Though a turbo kit can/could be more expensive. (Speaking of quality parts and not chink turbos for $100!)

With a low PSI system, you can skip the extra plumbing for an intercooler and yet still make very good power.

Ether way, at cruise, an engine that is pressurized producing a pound or two of boost will increase the mileage.

I just don’t know what the OP thinks what “exceptional economy” would be for what ever he has exactly. As well as what he thinks is a good get up and go factor. I would have no illusions of running mid 9’s and getting 38 mpg’s.

 

[HEMI-ITIS]

Economy and performance in a B motor can not be used in the same sentence.

There it is.Need boost or nitrous to make it happen.

 

[70chall440]

I definitely think it can be done but at what cost. No one would have believed someone would get 800 - 1000+ HP out of an engine but we all know this is relatively common. It all comes down to cost and effort; if $ is not a concern I think a B or even an RB engine could be built to provide economy and performance. But I would quickly say that as has been eluded to here; the engine is but one component of the over all system. The lighter the vehicle, the more aerodynamic is it, the better economy and one could argue performance it could have.

As always, it is about goals, objectives and money however I do believe there is a limit, don't know what they limit is but its there. How about alternative fuels; propane.... LOL

 

[Ray70Chrg]

Something like this.
View attachment 971506

Hey andyf, What is it you have going on there? What car, engine, specs, and cost if you care to share it with us. Looks like a great build.

 

[451Mopar]

Can a big block be built to make good power and still have exceptional fuel economy? I am just wondering if it can be done? What would it take?

Depends on how you define good power and exceptional fuel economy? Also, at what cost?

On the inexpensive side, a smaller carb, sharp tune-up and High rear gears (low numerical) will increase the economy, but with less performance.

The TBI Sniper EFI is pretty affordable and will make having a good engine tune alot easier, but won't address the drivetrain gearing.

Changing to overdrive transmissions with matching rear end gearing (rear gear will depend on the transmission gearing), is a bigger investment in cost and installation as many OD trans swaps will require trans tunnel, T-Bar crossmember modifications.

For the most part, these changes are done for driveability, not economy. Most people won't drive the vehicle to the point the additional costs are paid for by fuel savings.

With that said, my '69 Coronet Convertible is setup more for the long distance touring. It has a 440 stroked to 505", ported stealth heads, mild hydraulic roller cam, TTI headers, and the Edelbrock XT TPI type EFI Intake with FAST 2.0 controller. I likely have over $4,000 in the EFI system, so not that cost effective.
The Transmission is the old Kesiler SST-700 5-speed manual. The transmission was made by Legend Gear and Transmission as the LGT-700. it has a 0.68:1 overdrive 5th gear. Again, more $$$$ (maybe another $4,000?) and I did have to clearance the T-Bar crossmember.
When I was driving with the original Edelbrock EFI controller (non-self learning) I did not check the fuel mileage, but it seemed to be decent.
The new FAST self learning (wideband O2 Sensor) controller should be slightly better. I haven't driven the car yet in it's current configuration.
Converted the manual 4-wheel drums to power 4-wheel discs, and when bleeding the lines (stainless) a few connections were dripping, so I just got the Cool Tools Flare lapping tool.

 

[Johnpat]

If people start talking about the gas mileage I get,
then they don't want one.

 

[BSB67]

Can a big block be built to make good power and still have exceptional fuel economy? I am just wondering if it can be done? What would it take?

Define good power and exceptional fuel economy.

 

[wyrmrider]

my 59 Imperial got exceptional gas mileage for almosr 500,000 miles
maybe it was the fins
Gil Younger created a shift kit for the cast iron TF
over the years Gil used my AOD Ford, AODE Mercury (which just got me to Sequoia park and back- over 20 mpg) and the 518 in my 92 Dakota as R&D vehicles
I worked for Mike Ricker Nash/Rambler in Whittiwe and we ran in the Mobilgas economy ron
sub 3.08 gear and OD and lots of other tricks
I remember the lowest gear for the Rambler was 4.28 and I had 4.11 od in mine
(aluminum Nash Satesman 2 carb head and posi) went from t96 to "Pd.Taxi T86) and eventually a b&B/long clutch
My brother had 3.23 and od but i do not remember the tallest gear used with the cast iron hydramatic The hydro had a 4:1 low gear and no restrictions for running in third- so with a tall gear it was like a 3 speed with od trans. going away from that design was a big mistake till the built the turbo hydromatic..Rolls stayed wth the original design- smart move

 

[Paul_G]

Define good power and exceptional fuel economy.

Good power is 400 HP. Great economy is 15 city 20 highway MPG.

 

[Coronet R/T 68]

I've got a 68 coronet that has a 505 with a t56 6spd, 3:23 gears with efi. I can cruise at 75 mph at around 2200 rpm. Has about 600 hp, hauls *** and got 18 around mpg when I drove it from Erie Pa to myrtle beach. I plan on doing more work to get better milage, i.e. better cam and headers for more low end torque and switching to mpfi. Vs the holley super sniper I have now and possibly looking into low friction wheel bearings. I plan on traveling the US in it so milage is the goal

 

[BSB67]

Good power is 400 HP. Great economy is 15 city 20 highway MPG.

Okay.

I have not done it, never tried, and therefore do not have a definitive answer. I would generally say that if you use a carburetor, 3.23 gear, 4000 lb car, probably not. My 425 hp-ish 440 would get 12-13 mpg with no tuning for gas milage, and my foot constantly in the carb. Highway was only a little better. I think if you are using small tube headers, a regular Performer with a spreadbore carb and a O2 meter and tuning you might get close. Use a 2.76 gear and I think you can get there or real close.

Add technology based fuel management and/or 5 or 6 speed transmission, it should be easy.

Also, not all 400 hp engines are created the same. The above is predicated on a engine build focused on more efficient power.

 

[451Mopar]

For my setup, I am looking for 500+ HP (550 would be about the max I would expect with the combination?), Not sure about fuel economy, maybe 17 to 20 max?
In Overdrive, 50 MPH is 1,500 RPM. The engine does have real good torque, almost like my 24-valve Cummins Turbo Diesel.