Are you swapping big inch to little inch?

[66fs]

I went from a 273 to a 170 back in the Jimmy Carter years, but that was because I had to pull my favorite 273 because pump gas was not good enough for me to run it anymore. I also read about the Hyper-paks in the Baby Grand Nationals where they all beat all comers, and NASCAR dropped the series, true to form. It did get a bout 30 mpg highway cruising. Had lots of cool parts, but practically gave it away when I swapped a 273 back in. The guy who bought it had no idea all the cool stuff that engine had done to it. Can't get a smaller MOPAR V8 than a 273.

 

[Jim Lusk]

Can't get a smaller MOPAR V8 than a 273.

Not quite. 241...

 

[66fs]

Not quite. 241...

View attachment 1715962572

Nice, I stand corrected. Is it going to get a home?

 

[memike]

More Smiles per gallon

 

[jimjimjimmy]

who builds a stroker expecting fuel economy you build it for more tq and hp which means more oats to feed the horses . my stroker gets 13 m p imperial gallon and am very pleased with that , fuel economy is the last thing on my mind . now my daily is a different story .

 

[cpearce]

My W2 408 recently put down 17.89MPG (Imperial), on a 320 mile road trip, 2850 RPM constant. Proper timing, and the Edelbrock 800 AVS 2, are certainly helping.

 

[memike]

My W2 408 recently put down 17.89MPG (Imperial), on a 320 mile road trip, 2850 RPM constant. Proper timing, and the Edelbrock 800 AVS 2, are certainly helping.

Nicely done sir

 

[pittsburghracer]

Nicely done sir

That is good but keep this in mind. I had to refresh my memory

 

[memike]

That is good but keep this in mind. I had to refresh my memory View attachment 1715962704

Wow, I learned something today, thats quite a bit larger then a us gallon

 

[Jim Lusk]

Nice, I stand corrected. Is it going to get a home?

Not mine, just a pic I found on the net.

I used to own this one (Dodge 325), but I sold it in 2006 because I realized that I was never going to build a street rod and the money went a long way toward the purchase of the Barracuda convertible.

 

[Oldiron440]

My next RB will be a high winder, 7300-7500, 13.5 cr, 4.38 x 3.75 E-85 fueled 452, yep it’s going to be a fuel sipper…

 

[fishmens67]

I'm good with 451 ci if fuel stays under 10 bucks a gallon for 8-10 mpg.

 

[Syleng1]

Here's my economy engine. When a 273 is too big, go for a 241 cube Hemi.

View attachment 1715962349

That’s “wheelie pop-in” fun time there Mike.

 

[Jarlaxle]

As said in the OE post, a lot of stroker combos of rod which I can’t think of a singular stroker with a small cam and tall gear being built here yet.

“Oh yea guys! I have a 408 that gets 22 mpg with that factory dual plane and TQ! The real secret is the Isky “Mile-O-more” cam I have in there. What a broomstick!
I can’t wait to try the OD trans and 2.45 gears with my 3.15X15’s!!!!!


What’s decent mileage from a stock ‘70-440?

I might actually do that. Good heads, probably a dual plane (Performer RPM or M1) intake, mild roller cam, TQ carb...2.94 or 2.76 gears and OD. Might top 25mpg highway in a Duster. Friend did it...has a 408 stroker with I think the old MP aluminum Magnum heads, in an Aspen wagon with a low gear 999 and 2.76 gears. Done by just past 5000rpm...but pulls from 1500 and will top 20mpg on a road trip.

And looks like a 318 down to the vacuum lines and Lean Burn box.

Reminds me of an old saying from my days in engineering school (something like):
"It's more efficient to run a larger engine at low loads than a smaller engine at high loads". Within reason.

Spot on. That's how GM F bodies got such good MPG ratings in the 90s. That's how my 470hp, 4700lb Challenger managed 24mpg on a road trip despite 70mph speed limits.

 

[Jarlaxle]

My W2 408 recently put down 17.89MPG (Imperial), on a 320 mile road trip, 2850 RPM constant. Proper timing, and the Edelbrock 800 AVS 2, are certainly helping.

Sounds like you could use a well-tuned ThermoQuad and maybe a gear swap...

 

[cpearce]

Sounds like you could use a well-tuned ThermoQuad and maybe a gear swap...

Everything on these beasts is a compromise. Ideally I would have a Tremec, and EFI, lol

 

[Jarlaxle]

Everything on these beasts is a compromise. Ideally I would have a Tremec, and EFI, lol

There's no real compromise with a TQ. It might be the best street carb ever made. And most of them flow more than your AVS.

 

[cpearce]

There's no real compromise with a TQ. It might be the best street carb ever made. And most of them flow more than your AVS.

I'm actually quite familiar with the TQ, I agree it is a great street carb. The compromise I was more referring to is gearing, you get it right for performance and it isn't necessarily great for long drives. Car has 3.23 in it now, did have 2.94, but with the 4 speed and lighter flywheel it wasn't ideal for stop and start driving. Around town it would love 3.55, or 3.73 gears.

 

[Dave_J]

Aunt had a Chevy Kingswood Estate Wagon with the 400 SB 4bbl and 400 trans. It got 14 MPG on a long road trip.
Her new husband was a real Fart Smeller and decided to put his 283 2bbl and Power Glide in it for a road trip from Seattle to Saint Louis. It got the best mileage when they went thru Nebraska, 9 MPG but averaged a wopping 7 MPG for the trip. They could not even do the "Speed limit" back then.

If I had a 1970-75 A body and wanted to do good gas mileage but still have a lot of fun, a 4g63 2.0L with a BIG hair drier mated to a Baby 904 from a 1978-83 Sapparo or Challenger.

 

[Swinger 340]

I built the biggest small block I could. I'm going against the grain, because f&$% it. I'll be dead someday, and I won't be thinking about the $5.00 I saved per drive on my deathbed

I would rather have the fun. Everyone or families, need two automobiles, the Fun one and the everyday one.

 

[Swinger 340]

Wow, I learned something today, thats quite a bit larger then a us gallon

But not bigger than a Texas Gallon.

 

[MopaR&D]

Fuel economy was a high priority when I first got my Duster because it was my only car. Got all caught up in building a high-compression 360 to maximize efficiency but then realized after it was hooked to a 3-speed auto with cheap loose 2600-stall converter it didn't matter much. Without overdrive and EFI or spot-on carb tuning (and either lockup converter or manual trans) you can only get so much. Without overdrive, tall gears get good mileage on the highway but wreck in-town mileage and vice-versa.

I started building a mild 440 for my '72 3/4-ton Dodge truck because the 360 gets 10 MPG all the time no matter what. I figure it's the extra weight and terrible aero of the truck combined with the heavy full-floating Dana 60 rear end, the 727 definitely doesn't help either. I'm banking on the "bigger engine under less load is more efficient than smaller engine under more load" logic, hoping the mileage stays the same but double the HP and 1.5x the torque would be a welcome addition when towing heavier trailers.

Classic Mopars can get decent mileage but it takes a lot more than just putting in a smaller engine. Gearing, parasitic drag from transmission and rear axle, rolling resistance from tires, aerodynamics, weight... they all play a part. A smaller engine uses less fuel under the same relative light load as a bigger engine but a smaller engine in a heavy vehicle set up to withstand big block torque will be under more load and require more throttle opening to maintain the same constant power to keep the vehicle moving. This is also why putting a 7-1/4" rear and tiny 3-speed manual behind a 440 won't increase mileage because that big engine needs to burn a certain amount of fuel just to keep itself spinning and extra parasitic drag from heavy-duty driveline parts barely puts any more load on it than the power it's already making at cruising RPMs.