What is realistic MPG for a daily driven SBC?

I'm at about the same 16.9 mpg, 63 C-10, 77 tired 305, headers, duels, 3 sp man and 3.73 rear.

I just swapped to a '70 factory intake and a q-jet, with the OE 2 brl, I was at 10 mpg.

Last weekend I changed the "flex" fan for an electric and it looks like the mpg has gone up, no fill up yet.


My Dads 64 Chevy wagon (283 3sp) got 18 mpg highway loaded down for vacation (early 70's), and his 92(?) Roadmaster got 27 highway.

My old 77 T/A got 10 city and 22 highway, but it had 'go directly to jail gears'.

I think upper 20's highway with a carb should be do-able with a well tuned full size.

David

 

I totally hear you. Our newest car at this point is a 1986 Olds Cutlass (305-200R4). I have no idea what the mileage is because I don't care ... what I do care about is the fact that this car (we also have a '81 Buick Regal 231 V6) is too old to require emission tests (required every two years here in Toronto area of Ontario) and being carbureted, I can fix them when things go wrong. I keep an alt, a dist, and a fuel pump (and tools) in the trunk of the car just in case. I hate the fact that new cars are hard to fix (so much crap under the hood) and the fact that parts are generally very expensive (fuel pump direct from GM is $40 for one of these carbed engines, and I can change one on the side of the road in probably less than 15 mins ... try that with a fuelie).


My "jalopy"? '38 Olds coupe with a stock carbed 305 and a T5 stick. The Buick (bought off the 94 year old original owner and never winter driven) will be getting a carbed 350 and T5 soon.

I realize the intention of this post was to get actual numbers, and I realize you aren't getting any from me, just wanted you to see my point of view. The fuel mileage is not bad enough that you will catch me driving a Prius.

 

I had a 69 chevelle with a 307 and 2 barrel that got a best of 27 mpg on a couple of different road trips. Around town never better than 18 mpg. It had pretty tall gears and would have had trouble pulling a sick whore off of a pisspot, but it loved to stretch its legs on the highway.

and regarding weight, doesn't the chevy 6 weigh more than a small block?

 

my 35 truck gets about 18 fwy and 13-14 around town with a 283/th400, 500cfm carb, 3.73, and 7.00-16 rear tires.

it's no hot rod engine but it's still fun and it gets better milage than my newer truck so i drive it daily unless i have to haul something big

 

What an interesting post! The early reply with the early to mid-90s Buick wagon was extra interesting to me, since I recently garaged my previous daily driver '68 F100 flatbed (FE motor that I tuned towards 12 mpg), and was recently given a friend's customized '92 Olds Custom Cruiser, the TPI 350 has 203K on it, just had the trans rebuilt. I've been tuning it up, running Sea Foam cleaner in the block and tank,and just now beginning to measure mileage. It sure seems to be doing better than the flatbed. We'll see what the figures say. Interesting post, though!

 

BITCHIN' wagon btw,

 

Thanks "Ricky B"!
But getting back to "banjorear" issue: Another key element is an overdrive transmission. You had mentioned a 5 speed standard, I am running a 700R4, either way an overdrive is a must to obtain any kind of good MPG. Mixing the old technology with the new can and does work!

 

My experience with a late model Blazer is that you quickly get used to cruzing around 2000 rpm +/- in overdrive. NONE of my carbureted vehicles deliver good economy in overdrive at speed at that rpm. I think the intake speed slows down, is poorly distributed and the throttle is much farther open to maintain speed.

I get great mileage at 3200 rpm in 1-1 4th gear with a 350 in my 54 F250. .72 to 1 overdrive in the NV4500 cuts it in half. Probably overcammed/under geared.

Without getting too deep into specs, I have to conclude that a cam made for low rpm power, small carb primaries, correct gearing for your target road speed that allows the engine to operate in the middle of it powerband will deliver the best economy. Careful choices will deliver the economy you seek, a few miscalculations will cost you a lot of time and/or fuel.
Good luck.

 

good science here. I'd add low rolling resistance tires, good alignment, wax-on-wax-off!

 

Best mileage I ever got out of my chevy II was when it had a stock 283 2bbl T350 and 3.31 gears. It would get 20-22 all the time. That was better than the various 194/250 6 combos or bigger SBC's that were stuck in it consequently. I wish I would have tried that 283 with a 3spd OD.

 

I'm just about ready to convert my Wagon into a daily-driver to. The cost of a properly built 700R4 & convertor with the TV cable, etc look costly.

 

That would depend on your horsepower and torque numbers. My last 700R4 cost me $485.00 at a local tranny shop and it worked just fine. The one I have now is an Art Carr Performance 700R4 with a manual valve body (no T.V. cable) and a 9-1/2" converter. Price: $2500.00 to my door. The difference, 425 hp before and A LOT MORE NOW!

 

My '85 Elky has a mild 350 headers and a 700R4. It gets between 14 and 22 depending if I can keep my foot out of it.

 

About ten years ago, I bought an '86 T/A from a fellow employee that needed money fast. TPI 305/700R4 that regularly got 27 mpg on the highway.

 

Had a similar problem here in the UK where gas is $9.00+ a gallon.
Swapped my daily 63 F100 Y block 12 -15MPG for a 1990 Porsche 944S2.
Not a typical rodders car but fun to drive, on twisty road or a track it would run rings around a $25K+ Stang or Vette.
Porsche cost the same as I got for the F100, it gets 30MPG, and will do 149MPH and 0 - 60 in less than 7 secs a service kit for the Porsche is <£100, this year the Main Dealer Garage wanted £500 to service my wifes 2008 baby Fiat.
Prices on these Porsches have pretty much bottomed so unlikely to be worth less than I bought it for in 2 years unlike a similar aged family car, which are pretty much scrap value.
Rich

 

my 327 with 1.94/1.60 valve small chamber heads. steel crank,10.5.1 flat top race pistons,thinwall ceramic rings,4.68 lift cam,1.5 to 1 roller tip rocker,Weiand tunnel ram w/2 390 cfm holleys,th350 w/3:08 rear in a 3200lb car and I got 14 town/17 hiway on 93 octane.

 

I had two early 90s Chevy Caprices. One got 24 mpg and the other got 22 mpg. The newer one's transmission seemed to be a lot more sluggish and I am sure that is why it got worse mileage. Both engines were 350s. My friend's 73 Jag with a mystery small block gets right around 22 mpg with no overdrive. I think getting low 20s on the highway is within reach of just about any SBC.

 

got a 355 mild cam edel 4 headders electronic ign and i tweaked this one all the best ways i know and it got 17 on a long road trip once runs about 25oo at freeway speeds, never did a gas analysis as my machine broke and got thrown kinda disappointed, but maybee play with the right foot too often it in a 53 chev turbo 350 has a vacume gauge and runs about 10 to 12 inches on road got Rhodes lifters would be nice to do another mile or 2 per gallon engine starting to oil plugs and may have to build a 307 for it but would miss the power it cranks now

i have done a lot of 307 and 327 in chevelles and impala and run 20 to 22 MPG long ago they were dualed ,jetted, and at least big gap plugs some HEI but driven very light on the foot we run spred bore holleys and even the big GM 2 barrel, driveability was always close to a lean misfire on these and they were all set up on gas analysis which i felt getting the HC and CO down to small numbers always was good for the last 2 to 3 MPG

what is a good cruising RPM for milleage now days??

 

My 67 Malibu weighs 3400, has a 327 with double-humps, a 480/230 cam, a Holley 4777, backed by a 700R-4 and 12-bolt with 3.55's. I get 12-15 mpg stop & go, 21 highway. I put little pieces of wire in the idle circuit to lean it out for road trips. Last summer we took it out to Woodward. I pulled the plugs at a buddy's garage west of Detroit-- they looked brand new after 650 miles. Might be a little too lean.

 

Tell yer boss you really need a raise, and hammer that throttle. Life's too short to sweat the small stuff.

 

I'm currently driving a 305 sbc powered, 265,000+ mile, 84 Pontiac Parisienne back and forth to work, 50 miles one way, mostly hwy miles, but there are about 8 to 10 stops along the way. I'm getting 19-20 mpg and really trying. I know it gets better mpg if I could run 65-75 mph, but speed limits are 55 the whole way.

 

My wife thinks I'm nuts for keeping track of mileage on everything we own except her burb, since she puts in the gas and won't write it down.

My best recent mileage maker was the 63 Corvair I used to commute for about 4 years. Routinely pulled mid 20's out of it after some carb tuning.

Just about to make my 64 Camino my daily, de-tuned the 427 from a massive solid roller and 1000 cfm carb that got 12 mpg to a much smaller solid roller, only about .530 lift, and a 750 carb. Looking to pull close to 20 mpg with that setup. Car weighs in at 3806 lbs, Tremec TKO600, .82 overdrive, 3.55 gears, cruises at 24-2500 rpm at 70 mph.

Early 60's fullsize with a smallblock should weight in close to the same. Build the engine with short duration cam, small primaries on the carb and run it lean, keep the rpms at 200-2500 on the highway and you should do well.

My dad had a 66 Chevelle with a 283 that in completely stock form pulled 18 mpg on average without any special tuning.

Devin

 

When I was running my '54 Chev Panel with a stock '96 TBI-350 SBC, a 700R4, and a 10 bolt with 3:07's I got 18-19 mpg around town and 22 - 23 mpg on the highway. It was a great driver.

 

Well actually, that's not true at all...Here's what he said in his original post....



I'd be willing to put some money into the engine and use an EFI set-up and a modern 5 or 6 six speed trans (stick or auto) if that would help me to get more MPG.

 

Thanks "Ed"!
I stand corrected and deleted the post.
Funny thing is, I've been following this thread from the start.

 

This is the most accurate statement so far.....

I built this combination for the A coupe I just sold.

 

Thanks all. Yeah, I'd go with an A/M EFI set-up if it would a big difference (2-5 mpg), but you like to stay with carbs.

I noticed a few posters mentioned that they thought they could get better mpg at 65 mph vs. 55 mph. Curious on why?

Wouldn't, in theory, 55 mph lower the rpm's and thusly overall fuel consumption?

 

I just remembered, there was a tech thread a couple of years ago, well written by one of the guys that's been around here for quite a while, regarding performance and driveability of small cube small blocks. Maybe somebody else remembers better specifics and can post a link.

Devin

 

i goy good into the 20's with a 350 mild performance built, 650 edelbrock and overdrive 3.55 gears.

 

In Eng.-speak: each increase in velocity increases the HP required to do the work. and it's not simply % increase! It's to a power of exponent value. (I believe along the lines of: double the speed, four times the power needed)
So unless your setup has a power/efficiency curve and gearing sweet spot, that can best the above physics issue, ain't gonna happen.