Best gas mileage with big block, LOL
#1707417
12/06/14 09:47 PM
12/06/14 09:47 PM
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Kingston, TN
CudaMike
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Kingston, TN
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Re: Best gas mileage with big block, LOL
[Re: CudaMike]
#1707418
12/06/14 10:01 PM
12/06/14 10:01 PM
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Kalispell Mt.
HotRodDave
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No reason a BB HAS to get bad mpg. A 361 with tight quench and closed chamber heads should get nearly the same as a 360, just heavier and you can not use a 904 if you go automatic. I think the 904 is worth at least 1 mpg. The weight should only hurt in town. You could do the same with a 440 just gear it higher, you would need about a 2.2 gear to match a 360 with 2.76 gears, then again you are still stuck with a wastefull 727 if you go auto. You have to think of the gear ratio/CID as displacment per mile, for the example above you could run a 273 with 3.64 gears and displace about the same amount of air as the above 360 and 440. The smaller you can get that number the better, even up to the point you can barely keep it moving with 100% throttle, and engine is most efficent when you are using all of it's ability and not wasting energy, this is why the 8 speeds autos get matched with high rear gears to get the final drive ratio waaaaay down and MPG waaaaay up. This is also why they put a slant 6 in dump trucks, just barely barely enough power to get nearly highway speeds without any more displacement to waste fuel. Another bonus to running them loaded to the max is no extra friction than is necessary. Is this the most fun way to drive them? No but it is the most fuel efficient.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Best gas mileage with big block, LOL
[Re: CudaMike]
#1707419
12/06/14 10:21 PM
12/06/14 10:21 PM
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DAYCLONA
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Quote:
I had previously asked what was the best gas mileage anyone had gotten with a 360. Now I'm asking the same for the big block. I know, gas mileage and big block is a contradiction in terms.  But, for the very few for whom gas mileage was a consideration, what have you been able to accomplish?   
I have no real concern for gas mileage, it's not generally a consideration in my builds, but none the less any data derived is interesting....I've done large displacement HEMI and 440 builds, all multi carburated, all featuring an OD transmission, automatic or manual, with OD ranges in the .70 down to.64 range, dynoed HP ranges from 450 up to 600...and rear gear ratios between 3:55 to 4:10, usually running rear tire diameters 27" +/- 1"
my 1970 Charger running a 440/6 spd .64 OD 5spd TKO600, 4:10 DANA, 27" tires, dynoed at approx 450 HP can turn in upwards of 22 mpg while maintaining a 70 mph cruise speed on cross country driving events...then again I can knock it down to 10 mpg on the streets having some fun....same with some HEMI builds I've done, best I've seen is 16 mpg, but this is with a multi carbs, generally 500+ HP, deep gears, and no regard for obtaining high mpg fiqures
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Re: Best gas mileage with big block, LOL
[Re: DAYCLONA]
#1707420
12/07/14 12:53 AM
12/07/14 12:53 AM
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Joined: Nov 2010
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jersey
Spaceman Spiff
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Eddie miller got 15+mpg on his duster on drag week. And that's an all motor 8 second ride. Of course it is efi..
526 cubes of angry wedge, pushbutton shifted, 9 passenger killer!
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Re: Best gas mileage with big block, LOL
[Re: HotRodDave]
#1707422
12/10/14 11:52 AM
12/10/14 11:52 AM
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Joined: Jan 2005
Posts: 4,862
the frozen wastes...
Pale_Roader
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Quote:
No reason a BB HAS to get bad mpg. A 361 with tight quench and closed chamber heads should get nearly the same as a 360, just heavier and you can not use a 904 if you go automatic. I think the 904 is worth at least 1 mpg. The weight should only hurt in town.
Hahahahahaha. Yes... but WHY???
A 383 or a 400, sure, but why put a 361 in there for any reason? And... i will dispute your reasoning too. The 361 was designed and built around the time when Napoleon was still alive. The 5.9L Magnum is aeons ahead ov it in every way, efficiency-wise. The ONLY thing they even come close to sharing is CID. Hell... even 90% ov the modern aluminum big block heads are still breathing through 60's and 70's designs, and ironically enough, the very few good designs out there are the ones no one uses (Chapman, B1, etc.).
Internal mass, friction, stacked tolerances/shoddy craftsmanship (gawd-awful factory balance), heads designed in 1959 (well actually, released in 1959... likely designed earlier) THE FIFTIES!!! Sheer mass and weight, utter lack ov modern efficiency-specific aftermarket (save maybe cams), and as you mentioned, much harder to get a nice modern (whether A500 or 5-speed) transmission behind.
I thought a LOT about this. More mental masturbation than i suspect anyone here bothers with... I just could not see a point in spending a small mortgage to make an efficient 383 or 361. And i was a DIE-HARD big block guy. Yeah... i could... do better than people have done... lets say 361, light zero deck pistons, Chapman 235 heads or B1BS (ported for the goal), optimized intake/carb/ignition, compression, super slick balance, custom cam... blah blah blah... only to be passed by some guy in a nicely tuned 360 Magnum while i'm pumping gas again.
So yeah... you could, but why? You're talking a 40 year chasm ov engineering, most ov which was spent in an efficiency-obsessed era, competing with imports and smaller Fords.
Build an efficient big block in an efficient car, and have a LOT more fun than Mr. 440/509 cam/4.10 gears... (do it right and you'll be faster too) but dont waste a dime trying to out-MPG a smallblock.
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Re: Best gas mileage with big block, LOL
[Re: CudaMike]
#1707425
12/10/14 12:46 PM
12/10/14 12:46 PM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
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Irving, TX
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19.5 mpg the original twin turbo 440 in my 65 Belvedere. It had 3.23 gears and an OD833.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: Best gas mileage with big block, LOL
[Re: Pale_Roader]
#1707426
12/10/14 04:40 PM
12/10/14 04:40 PM
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Joined: Jan 2005
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Kalispell Mt.
HotRodDave
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Quote:
Quote:
No reason a BB HAS to get bad mpg. A 361 with tight quench and closed chamber heads should get nearly the same as a 360, just heavier and you can not use a 904 if you go automatic. I think the 904 is worth at least 1 mpg. The weight should only hurt in town.
Hahahahahaha. Yes... but WHY???
A 383 or a 400, sure, but why put a 361 in there for any reason? And... i will dispute your reasoning too. The 361 was designed and built around the time when Napoleon was still alive. The 5.9L Magnum is aeons ahead ov it in every way, efficiency-wise. The ONLY thing they even come close to sharing is CID. Hell... even 90% ov the modern aluminum big block heads are still breathing through 60's and 70's designs, and ironically enough, the very few good designs out there are the ones no one uses (Chapman, B1, etc.).
Internal mass, friction, stacked tolerances/shoddy craftsmanship (gawd-awful factory balance), heads designed in 1959 (well actually, released in 1959... likely designed earlier) THE FIFTIES!!! Sheer mass and weight, utter lack ov modern efficiency-specific aftermarket (save maybe cams), and as you mentioned, much harder to get a nice modern (whether A500 or 5-speed) transmission behind.
I thought a LOT about this. More mental masturbation than i suspect anyone here bothers with... I just could not see a point in spending a small mortgage to make an efficient 383 or 361. And i was a DIE-HARD big block guy. Yeah... i could... do better than people have done... lets say 361, light zero deck pistons, Chapman 235 heads or B1BS (ported for the goal), optimized intake/carb/ignition, compression, super slick balance, custom cam... blah blah blah... only to be passed by some guy in a nicely tuned 360 Magnum while i'm pumping gas again.
So yeah... you could, but why? You're talking a 40 year chasm ov engineering, most ov which was spent in an efficiency-obsessed era, competing with imports and smaller Fords.
Build an efficient big block in an efficient car, and have a LOT more fun than Mr. 440/509 cam/4.10 gears... (do it right and you'll be faster too) but dont waste a dime trying to out-MPG a smallblock.
I did not say it was smart and I said "NEARLY" I did not say it would ever get the same or cost effective. The only thing a BB has over the SB is if you use a closed chamber head you get a bigger quench area because of the retarded valve location on a BB. I agree however that all the good things about the magnum far outweigh that.
Going from 15 to 20 mpg is easy, a lot easier than going from 20 up to 25.
BTW Feets example builds on my point about the displacment per miles, he effectively had a 2.29 final drive ratio and no auto trans to soak up MPG. My "superduper mpg 318" had 2.76 gears and got around 26 mpg in similar conditions. I displaced around 640 CID every wheel revolution and his 1021 CID per wheel revolution. Put that in a ratio and it is not far off the ratio of my MPG to his, remember I had an auto sucking a little extra fuel from mine and I think he had EFI also. That is generally how I figure if some is full of crap when they told me there car got X amount of MPG. Things like drag and frontal area gain importance with speed but as long as your tune is right then that seems to be the most consistent factor, all the tech tweaks help but how much air (and consequently fuel and engine friction) is displaced over a mile is the biggest thing.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Best gas mileage with big block, LOL
[Re: HotRodDave]
#1707427
12/10/14 07:03 PM
12/10/14 07:03 PM
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SomeCarGuy
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I had a 383 RR that got over 20 on the highway quite regularly, once knocked down 25 on one trip. Was shocked.
It was a 67 model long block, had the small OEM cam, HP manifolds with 2.5 pipes out the back, X pipe, electronic conversion, 600 Eddy carb. IIRC that carb is the most economy tuned OOTB from Eddy. It was running in the car when I got it, I added the Petronix and the exhaust.
Had 727 and I never checked the gear, but suspect it had a 2.76 or 2.94 in there. Certainly no more than a 3.23. Was a vert and had no tach, so I no idea what cruise RPMs were. Had stock 14 inch wheels/tires.
I want my fair share
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Re: Best gas mileage with big block, LOL
[Re: lewtot184]
#1707429
12/10/14 07:54 PM
12/10/14 07:54 PM
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Joined: Jul 2006
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California
mickm
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Quote:
folks, i think all these high numbers are from uncorrected speedo's. there is a reason the feds stepped in and forced detroit to use accurate speedometers. a 440, mostly stock, with a 3.23 rear and 15" wheels and tires is a 13-15mpg deal. i've danced thru this for years correcting the speedo, very good tune-up, careful driving and thats all they're gonna do. a 2.76 rear might help those numbers 10-15%, but i seriously doubt anymore than that.
i can get that with my 540. 2 650 edelbrocks running 1:1, vacuum advance, 4 speed with 3:54's but a 28" tire. 70mph straight, flat cruising.
as long as i keep my foot out of it, and i've calibrated the speedo, it is correct.
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Re: Best gas mileage with big block, LOL
[Re: lewtot184]
#1707430
12/10/14 11:52 PM
12/10/14 11:52 PM
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DAYCLONA
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Quote:
folks, i think all these high numbers are from uncorrected speedo's. there is a reason the feds stepped in and forced detroit to use accurate speedometers. a 440, mostly stock, with a 3.23 rear and 15" wheels and tires is a 13-15mpg deal. i've danced thru this for years correcting the speedo, very good tune-up, careful driving and thats all they're gonna do. a 2.76 rear might help those numbers 10-15%, but i seriously doubt anymore than that.
Maybe back in the day speedometer error was rampant?...my speedo has been calibrated, plus when setting up an OD 5spd you spend a lot of time changing speedo gears to "re-calibrate" the speedo to read accurately
Trust me. this guy more than confirmed my speedo was indeed accurate 
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Re: Best gas mileage with big block, LOL
[Re: lewtot184]
#1707431
12/11/14 01:12 AM
12/11/14 01:12 AM
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Joined: Jan 2005
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Kalispell Mt.
HotRodDave
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A 3.23 gear with a .71 overdrive is 2.29 final drive ratio. It helps a bunch. I think I could get 30 mpg@70mph in a dakota I am building if I change a few ingredients 
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Best gas mileage with big block, LOL
[Re: HotRodDave]
#1707432
12/11/14 01:55 AM
12/11/14 01:55 AM
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IN
ahy
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Mine's a 496 "B" with a moderately aggressive 243@.050 cam, .81 OD, 3.23 rear, EFI and 25.x" tires. I get a consistent 14 MPG cruising at 75 or so. The EFI and OD help a lot I think. pretty good for what it is.
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Re: Best gas mileage with big block, LOL
[Re: HotRodDave]
#1707433
12/11/14 11:09 AM
12/11/14 11:09 AM
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the frozen wastes...
Pale_Roader
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Quote:
Going from 15 to 20 mpg is easy, a lot easier than going from 20 up to 25.
Definitely. My goal is a bit different. The goal is 30mpg. Whether i get there or not is moot, as the REAL goal is to be able to get that 20mpg while driving like a complete ass.
That why i love my 96 Mustang GT... 4.6, EFI, 5-speed OD stick, 3.27 rear (i'd prefer higher... i think they made a 3.06?), sorta-light (3400lbs) aerodynamic car. I can drive like a tool and still get good MPG. No fun building a car that needs to be granny driven to pass a gas station.
My 72 Charger was just all-out no fun. Its junk 76 NY 440 with basic mods (750 3310, SD intake, Hookers, small cam, no options) and no compression got utterly vile MPG. It just wanted more gas. Had that 750 jetted to 80's and it was still lean (and i utterly refused to put a bigass DP on there) It had a 727 and 3.23's, but there had to be something wrong with the car itself. It was very well-tuned and it got 8MPG. I know Hemi guys that cant drive that got better than that. That car was tuned... and it was way faster than it should have been, but it sucked gas like i had a half tank ov nitro in there...
No fun at all.
On the other hand, back in my lowriding days, cruising my stock 71 383-2bbl (727/2.76) Fury III i could pull well into the 20's MPG. Though never driving above 55 helped.
That was the best and the worst i've ever gotten from a big block Mopar. Incidentally... my 6000lb 68 Cadillac hearse with its hi-comp 472 (big 800QJ), TH400, TWO driveshafts and aero that would make Feets look good gets 11-12MPG turning 31" mud tires. Thats with a 20 year old tune and a bog in the Q-jet you could drive a funeral procession through....
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Re: Best gas mileage with big block, LOL
[Re: lewtot184]
#1707434
12/12/14 04:53 PM
12/12/14 04:53 PM
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SomeCarGuy
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Quote:
folks, i think all these high numbers are from uncorrected speedo's. there is a reason the feds stepped in and forced detroit to use accurate speedometers. a 440, mostly stock, with a 3.23 rear and 15" wheels and tires is a 13-15mpg deal. i've danced thru this for years correcting the speedo, very good tune-up, careful driving and thats all they're gonna do. a 2.76 rear might help those numbers 10-15%, but i seriously doubt anymore than that.
You're not the only one that has ever checked a speedo for accuracy. It's not hard and those that actually pay attention to MPG are the ones most likely to have done so.
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