Hey guys, so i bought a 69 chevelle malibu 307 for me and my pops last summer as a birthday present to both of us and we have been slowly getting some progress on it. but i have a few questions about gas mileage. obviously none of us bought our beautys looking for good gas mileage, but i am just wondering what you guys have noticed.

we know we are going Big Block, thats a given. i am just writing this post trying to find out what people are seeing as real mpg with their big blocks?? i wanna use the car for mostly street use, but still burn it down the track on sundays, and am kinda trying to decide what motor we should look at. i would love to be able to drive it on a regular basis without having to stop at the gas station every 10 minutes...

454 / 496 / 502 / 540??

if you guys had any ideas about your MPG with any of these engines i would greatly appreciate feedback..

thanks alot and look forward to hearing from you guys

I get maybe 8-10 mpg with my 496 with normal driving. I get 10 gallons per mile when I bury it!:D

461 cid BBC, healthy solid flat tappet camshaft, Q-jet, 1 7/8" headers, 2.5" exhaust, dumped before the axle. '72 Camaro with 3.73 12 bolt rear differential.
Averaged 20+ mpg on a 2500 mile cross country interstate drive.

With my current setup,LS6 454 roller cammed Doug Nash 4+1 5 speed and 3.00:1 rear gear,I am getting close to 16 mpg (Canadian) on the highway at cruising speed.Put your foot in it and you can watch the gas gauge drop.
Guy

I built a 70 SS 454 Sta. Wgn. Have a tlr. queen this is my driver.
70 454-Q-Jet-- 700R4 overdrive--3:08 rear-12 bolt.
On the interstate 19-20 MPG. at 75 MPH. 454 is turning 1950 RPMs. Driving it to Nashville again this year and to Buffalo and to Can Am show by Toronto Can. and to Woodward, Ave cruise Detroit Mich.
Life is to short--ENJOY !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Bob:hurray:

454 / 496 / 502 / 540??

if you guys had any ideas about your MPG with any of these engines i would greatly appreciate feedback..

thanks alot and look forward to hearing from you guys


Mine is on my License Plate..

http://www.boomspeed.com/mc71454/May2006launch.jpg

Is this question allowed?

I averaged about 6 MPG. :) Darn I miss that engine!

It is hard to say what you will get with just an engine displacement as there are a lot of variables. Research your transmission / rear end combos - keeping your RPMs down on the highway is key.

how you guys getting so good of gas mileage? What trans and stall are you running? Ive got a 407ci 750 holley, th400, 3000 stall, 2.56 rear gears and I get a best of 10 on the hwy... I got 7 with my 650 holley

how you guys getting so good of gas mileage? What trans and stall are you running? Ive got a 407ci 750 holley, th400, 3000 stall, 2.56 rear gears and I get a best of 10 on the hwy... I got 7 with my 650 holley

without knowing too much about your combo, i'd say to get a tighter converter and deeper gears- like maybe a 3.08 or 3.42 or so- to allow the engine to breathe a little better at highway speeds. also, get rid of the Holley carb and get a well set up q-jet on a dual plane intake like the RPM qjet.
overall, the car might end up faster when you get on it, and get better mileage when you're not on it.

I average 12 mpg...I would love to know what I would get if I actually did not get on the gas all the time...can't help it...:D

This is with a crate ZZ502, TH400, 3,000 stall, 4.11 gear, but the helping hand here is my gear vendors under/overdrive which gives me a 3.22 in overdrive...;)

Oh yeah, this is in a heavy Monte Carlo.

I get this question all the time, and my answer is that It's not my daily driver and I don't care and will never check it. Its a BBC topped with a Holley and 4.10 gears so it sucks gas!!!! Gotta love displacement!

About 60 miles from a 15 gal tank of premimum unleaded.:yes:

Bill, is that with your 540? That is impressive!!!!!!

Bill, is that with your 540? That is impressive!!!!!!

You think so??? :noway:
That's burning 15 gallons in about 60 miles...approx 4mpg.
And most of that was downhill...both ways.;)

I'm just now starting to do some driving with my bbc 69 pick-up. I filled up the tank, drove ~75 miles (normal driving, not heavy footed) and filled it back up with 18 gallons. So about 4mi/gal. This is a mild bbc too. I do need to go thru the carb tho.

I didn't know there was such a thing as "gas mileage with a big block"....

But to answer the question, not sure about mine, seems I don't get much out of it before I gotta fill it up again. I'd guess between 6 and 10 mpg.

Must be why the critics call them "Pig blocks".

how you guys getting so good of gas mileage? What trans and stall are you running? Ive got a 407ci 750 holley, th400, 3000 stall, 2.56 rear gears and I get a best of 10 on the hwy... I got 7 with my 650 holley

Not sure...
My ZZ502 with an Edelbrock EPS 800 carb, Turbo 400 with 325 gears is getting 13-15 mpg in town with my foot out of it and about 8 when I'm having a really good time!

how you guys getting so good of gas mileage? What trans and stall are you running? Ive got a 407ci 750 holley, th400, 3000 stall, 2.56 rear gears and I get a best of 10 on the hwy... I got 7 with my 650 holley

THe 2.56 gears are good - but are they working well with your convertor?

What is your initial and total timing? How much vacuum advance do you get? (Are you running a vacuum advance on your distributor? Vacuum advances are needed for economy on the street).

About 60 miles from a 15 gal tank of premimum unleaded.:yes:

yup, about the same here :yes: :D

:D I love it

Mine is on my License Plate..

http://www.boomspeed.com/mc71454/May2006launch.jpg

Used to brag about the 16+ on the highway, and yeah, strictly the highway, no screwing around, and you might pull 16-ish with the trips. Around town!?. Kripes, went about 100 miles or so in the last few days and must have burned near ten gallon. Yeow!

Tom, havent seen that plate yet. :thumbsup:

I use 4 gallons of gas to go 10 miles to and 10 miles from the track in town and making about 6 passes. THat is with 3.73's and a 9" converter. EFI too. Big solid roller.

Guys I help convert drag only cars to EFI actually report using a LOT less gas just warming up, driving through the pits and racing on a normal weekend.

I thought I'd check back in on this thread.

Yesterday, I had the chance to drive my truck from home to my mom's house on Galveston Bay. About 160mi round trip, mostly highway @65-75mph. I averaged 12mpg. Not sure what happened on the previous tank other than alot of idle time in the driveway playing with the engine. Just wanted to correct/clarify my previous results.

I'd like to know what did the L34 and L78 396 engines in 1970 get for gas mileage when coupled to a TH400 and....let's say a 3.31 gear, or a 3.73 gear, or even a 4.10 gear.....?

Musclecar TV said yesterday an LS6 with a 4.10 outback got 8 mpg..........if you kept your foot out of it.......

not a BBC but I get 6mpg around town messing around and about 12 on the highway in 5th gear (.64) with my foot out of it

18mpg with 2.73 gears, 2500 stall, well tuned 396 motor with a holley 3310.

13.50 at 107 + mph on street tires.

12 MPG turning 3700RPM on the interstate.

Be smart, and get yourself some overdrive!!!!

454 with 5 speed, 15 on the highway:hurray: , 10 in town:yes: , 5 when having fun:sad: . Jb

A guy I know has a '68 with a 325/396 and a four speed. I was checking his car out and realized it had a ten bolt in it. When I asked he said the 3:31 12 bolt and muncie are tucked away in the garage and the car is running 2:73's with a saginaw so I can afford to drive it. He said he averaged about 10 mpg and that went up to 18 or 19 with the rear end swap, but the muncie didn't like the 2:73 gear.
Paul