I've been wanting to rebuild an engine for sometime (and if I work enough this summer and get the money for it I intend to), but have been told to stick with small blocks as you can still get a great amount of power from them and still have better gas mileage compared to big blocks. Now, I know it would seem obvious, but I want to check and make sure there aren't any little loopholes that I don't know about or anything, but do big blocks really get 'worse' gas mileage just due to their size?
Big Block VS Small Block gas mileage
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soccerguy045
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I've been wanting to rebuild an engine for sometime (and if I work enough this summer and get the money for it I intend to), but have been told to stick with small blocks as you can still get a great amount of power from them and still have better gas mileage compared to big blocks. Now, I know it would seem obvious, but I want to check and make sure there aren't any little loopholes that I don't know about or anything, but do big blocks really get 'worse' gas mileage just due to their size?
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4,856 Posts
All I can tell you for sure is my 70 SS with a MILD 427, "272" cam, headers, rpm intake, 750 vac secondary carb, 4 speed 331 gears gets about 13mpg on the highway at 65 mph.
My 66 Nova SS 327 L79 clone with 4 speed and 3.08 gears gets 18mpg at 70mph.
I know, apples and oranges but the best I can give you.
Ron
My 66 Nova SS 327 L79 clone with 4 speed and 3.08 gears gets 18mpg at 70mph.
I know, apples and oranges but the best I can give you.
Ron
If you are concerned about getting good gas mileage, buy a compact car with a 4 cyl. If you want a Chevelle with some muscle, put in a big block
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Honestly, I would think that a 350 with a comparable combo would get better gas mileage than a 396 or 454...
Honestly, I would think that a 350 with a comparable combo would get better gas mileage than a 396 or 454...
Seems to me that that should be a simple answer. Just depends on how much fuel you are running. You can't really say that a SB or a BB gets worse gas mileage. I personally favor small blocks because I don't need to get more than 500-600hp out of my engine (in my opinion BB are only a good idea if you plan on producing more than that), i like high reving engines, they are lighter, and parts are cheaper. Just my .02.
Like Texas70 said, if you are concerned about gas mileage get a compact car. Fuel economy shouldn't be a factor when working on building serious power. (unless it's for cruising?)
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Again...just my opinion.
Why else would I drive a 95 civic (did an engine swap on her so she's faster than she seems wha haaa but still slow as dirt
) if it wasn't for the gas mileage? Getting about 35-40mpg! I like that for commutting.
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Like Texas70 said, if you are concerned about gas mileage get a compact car. Fuel economy shouldn't be a factor when working on building serious power. (unless it's for cruising?)
Why else would I drive a 95 civic (did an engine swap on her so she's faster than she seems wha haaa but still slow as dirt
) if it wasn't for the gas mileage? Getting about 35-40mpg! I like that for commutting.
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11 Posts
with my setup
sb 406 with 3.90 gears and a th350 and a 295/50 r15 on the highway with a 3000 stall cruising at 65
i got 14mpg. thats pretty good in my book for a car that runs a mid 12 and no overdrive.
rick
sb=economy gas guzzler
sb 406 with 3.90 gears and a th350 and a 295/50 r15 on the highway with a 3000 stall cruising at 65
i got 14mpg. thats pretty good in my book for a car that runs a mid 12 and no overdrive.
rick
sb=economy gas guzzler
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18,738 Posts
Simple physics man. take ( rpms) X (displacement )X( throttle opening %) at a given rpm and you get a fuel consumption number. This isnt a real empirical formula, but you know what I mean.
So, of course, a 355 will consume less at 2800 rpms than a 454, all else being equal.
You want a rat that doesnt eat much gas at cruise. Use a 3X2 intake. Otherwise you'll be in the 13-14 range , and that isn't bad. 3X2 will get you 15-18. Non overdrive 3000 rpm numbers.
So, of course, a 355 will consume less at 2800 rpms than a 454, all else being equal.
You want a rat that doesnt eat much gas at cruise. Use a 3X2 intake. Otherwise you'll be in the 13-14 range , and that isn't bad. 3X2 will get you 15-18. Non overdrive 3000 rpm numbers.
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341 Posts
Now that's what i'm talking about !! "Big Block's Rule"
Whats Gas Mileage???? Chevy,... HUH?
1985 350 Small Block/Monte Carlo SS
$60 Per Week Daily Driver
1971 Chevelle SS 396 Big Block
Last Summer Daily - $80
Welcome to my world !!!!! And as sad as this is compared to my girl friends 4 banger,... that costs her $10 Per week,... I still love both these cars and can't seem to make myself believe that I need a 4 cylinder,... Drowning!
Dan
1985 350 Small Block/Monte Carlo SS
$60 Per Week Daily Driver
1971 Chevelle SS 396 Big Block
Last Summer Daily - $80
Welcome to my world !!!!! And as sad as this is compared to my girl friends 4 banger,... that costs her $10 Per week,... I still love both these cars and can't seem to make myself believe that I need a 4 cylinder,... Drowning!
Dan
G
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·Heck, buy yourself a Metro three-door hatch, 3-banger, corn-popper car to commute with AND play with shear hp on the weekend!
You will love the 40 to 50 mpg!! Depending on the way you drive b/c I can hit 50 pretty regular in my 2000 Metro!!
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
You will love the 40 to 50 mpg!! Depending on the way you drive b/c I can hit 50 pretty regular in my 2000 Metro!!
pdq67
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
He's an unusual deal.....when i was driving my chevelle on the day i got it i got 22mpg. lol NICEEE (usually got 15mpg) I had a 1979 delta 88 back in the day that got 8mpg. Kinda funny when you upgrade to a muscle car that gets better gas mileage than your daily driver.
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6,190 Posts
PDQ...you may get excellent fuel mileage,but I'd hate to be in a wreck in your GEO vs. my 98 Chev.ext.cab peekup or a tractor trailer for that matter. I'll gladly take the 15-19 mpg and safety vs. 50 mpg.
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heck,at 6'3" 285 I don't think I'd fit in a GEO
We have five vehicles:
'69 Vette 427
'72 Chevelle 350
'93 Vette 350
'95 Jimmy 6 cylinder whatever engine
'98 Jimmy with same whatever engine
No-one ever believes that a Corvette gets the best gas mileage but the '93 gets between 23-24 highway and the next closest one is the '98 Jimmy with 19 highway. The '69 Vette is 15-16. The other two are right around 14 mpg highway. I really thought the Chevelle would have done better than that. ( and no, it doesn't seem to drive like it needs a tuneup
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'69 Vette 427
'72 Chevelle 350
'93 Vette 350
'95 Jimmy 6 cylinder whatever engine
'98 Jimmy with same whatever engine
No-one ever believes that a Corvette gets the best gas mileage but the '93 gets between 23-24 highway and the next closest one is the '98 Jimmy with 19 highway. The '69 Vette is 15-16. The other two are right around 14 mpg highway. I really thought the Chevelle would have done better than that. ( and no, it doesn't seem to drive like it needs a tuneup
I agree with pegleg. My daily driver is a 1999 Honda Acoord V6 that gets pretty good gas mileage. It also has 200 hp and is a kick to drive in the Houston traffic down Westheimer every morning and evening. On weekends I will not worry about gas mileage (when my chevelle is finished). Fill the fuel cell and when it's empty, fill it again
BTW, a big block automatically has more power than a small block......
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![Image]()
lol
BTW, a big block automatically has more power than a small block......
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18,738 Posts
WTF are we talking about 1200cc motors here???
Oh and BTW, if I whomp on my big block at all, its 10-11 mpg.
Now John 71350SS has an excellent thought. According to my ROUGH equation, a 406 bbc and a 406 SBC would have identical gas milage given identical DCR's temps, gears, chassis, etc.
Wonder if the smaller intake runners of the sbc help here???? That would effect the "throttle opening %" of the equation.
But I really don't give a rats arse about Geo's. I had a Spectrum, it got 35, SO WHAT!
I beleive this is in PERFORMANCE!
Oh and BTW, if I whomp on my big block at all, its 10-11 mpg.
Now John 71350SS has an excellent thought. According to my ROUGH equation, a 406 bbc and a 406 SBC would have identical gas milage given identical DCR's temps, gears, chassis, etc.
Wonder if the smaller intake runners of the sbc help here???? That would effect the "throttle opening %" of the equation.
But I really don't give a rats arse about Geo's. I had a Spectrum, it got 35, SO WHAT!
I beleive this is in PERFORMANCE!
more power = more fuel
I bet if you had a mild 396 or 402 BB that was not making much power and compaired it to a really built 350 making tons of power, the BB would get better fuel milage. But why have a BB if it is going to be so de-tuned? Muscle cars are not for fuel milage. build it to go fast, big or small block depending on which you like and forget the fuel milage.
About geo metros: I don't really like them, but my friend had a brand new one and we were riding in it just a few days after he got it. Some cell phone wielding soccer mom in a minivan ran a stop sign and t-boned us in the pass side (where I was sitting), which in turn turned the metro to be skidding sideways in the lane of oncoming traffic where another van, this time full size, t-boned us in the drivers side. the van was going about 50mph and were were doing about the same. THis all happened in a matter of seconds. The impact from the second van actually threw the little metro about 15 yards back before the intersection that the first van ran. My friend and I basically walked away. We both had concussions, glass cuts and such, and he had a broken rib. the car was a mess. So, although I still don't think they are as safe as a bigger car, they are safer than they look, othewise I wouldn't be here today.
I bet if you had a mild 396 or 402 BB that was not making much power and compaired it to a really built 350 making tons of power, the BB would get better fuel milage. But why have a BB if it is going to be so de-tuned? Muscle cars are not for fuel milage. build it to go fast, big or small block depending on which you like and forget the fuel milage.
About geo metros: I don't really like them, but my friend had a brand new one and we were riding in it just a few days after he got it. Some cell phone wielding soccer mom in a minivan ran a stop sign and t-boned us in the pass side (where I was sitting), which in turn turned the metro to be skidding sideways in the lane of oncoming traffic where another van, this time full size, t-boned us in the drivers side. the van was going about 50mph and were were doing about the same. THis all happened in a matter of seconds. The impact from the second van actually threw the little metro about 15 yards back before the intersection that the first van ran. My friend and I basically walked away. We both had concussions, glass cuts and such, and he had a broken rib. the car was a mess. So, although I still don't think they are as safe as a bigger car, they are safer than they look, othewise I wouldn't be here today.
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