So, Can you have a Old-Style carbed V8 and get 25+ MPG?

glad to see so many that under the concept of final gear ratio. this has a much to do with gas mileage as fuel injection and computor mangement. when you have all three thats how current new cars do so well, but its cheap and easy to at least get the right gear in you old ride.

 

olds 455s from early to mid 70s in delta 88s when in good tune, wille regularly knock down 20mpg. that is w/qjet and single exhaust. installed in a lighter weight car with a few mods, it should peel up asphalt and still get 20+ mpg. buick and cadillac engines also could get close to the same numbers. the secret here is in the q-jet carb, i know a lot of guys don't like them but when properly set up they will give you good drive abilty with descent performance. they are harder to tune than a holley, keep in mind the design was licensed by solex and used on mercedes. they also appeared on 429scj in mercury marquis's on the police package.

 

$2.00!! Damn, we are at $3.80 here is SoCal...

I do remember seeing an old Rod & Custom or Hot Rod that had an article about setting up your 3 duece setup to get 20+ MPG...and this is in like '56 or '57...I'll look for it when I get a chance and post...

 

One of Popular Hot Rodding magazine editors had a 70-72 Monte Carlo that he built to get good gas mileage. They did a series of articles on what was done to it to achieve good gas milege. Seems like it had everything except a/c and ran a 2.79? rear gear. Had a vacuum gauge, got in the mid to high 20's if I remember correctly.

 

You jogged my memory banks when you montioned the Popular HotRodding Monte Carlo Project from the '70's. I think Doug Marion was the editor back then, and they built the engine using one of Holleys baby Q-jet replacements. I wish I had a copy of that article to review........

 

of course its possible - i got a 350 sbc with a tri-carb, 3 94s. they all work on a progressive linkage, none of them blocked off. this is backed up with an ali powerglide, manual valvebody, 9" backend with 3.55s.

i normally get about 26mpg when im out and about. this is all in an all steel '35 5 window with a full interior, its a heavy car.

ive got a vw golf for my daily driver and i dont get much more than that when im out in that.

 

I am trying to get 25mpg out of my fleetline when its on the road.

3.73 rear gear, TH700-4R, and a carb'd 4.3L V6! I think I am going to try a Q-jet on the thing to see if I can get some milage out of her.

Anyone have a 4.3L HEI kicking around? I would like to put one of those in this thing.

 

Hmmm...

If I was building one, it would have:

• Short stroke (283/305 chevy, 260/289 Ford, 273 Mopar)
• low tension 'thin' rings
• roller cam
• roller rockers
• electric waterpump
• electric fan
• T-56 transmission - allows for a tall O/D and short final drive for fun
• Q-jet carb on a dual plane manifold
• tri-Y headers
• mild cam
• mild heads
• moderate comp ratio

the combo will make good power, wind to beat the band when you want it to, and push 30 MPH on the freeway. The keys here are the reduction of parasitic losses throughout the motor - AND - optimizing volumetric efficiency at a SPECIFIC speed. The engine won't make huge HP figures as the static pressure losses at max RPM will limit the motor's ability to flow - but when it's tuned to run as well as it can at, say...2500 RPM, it will be fun to run and make good MPG to boot.

A realistic goal would be 28 MPG @ 65 MPH inna fenderless Ford body.

 

The electric pump and fan blows the "old-style" right out of the water. I wonder what difference keeping the mechanical pump and fan would make, if you did all the other the same...

 

My non HAMB friendly toy (90 Mustang GT convertible) gets 23-24 mpg highway on short trips under 150 miles. It's a 302 and has a mild cam, roller rockers and 3.73 gears with a 5 speed stick. It also weighs 3600 lbs.

I am confident that in a sub 2000 lb bucket I can pull between 25-30 mpg with little trouble.

 

There are electric 'old style' pumps available which use an idler pulley to 'replicate' the look of a mech pump. As for an 'old style' electric fan - there's a thread on this here on the HAMB.

the difference is pretty significant - parasitic losses at freeway speeds may be as high as 20%...

 

So instead of 30 MPG, you may get 24? I could live with that! What kind of HP, and more importantly, torque, would a combo like that put out, est.?

 

One item that is rarely talked about that could help both power and efficiency is a crank case pump.

Just read about a 347 stroker Mustang that picked up 50hp at the wheels with a vacuum pump. They disconnected it and lost 50hp, hooked up and got the same power it had the first time. NOTHING else was changed.

 

24? Sure!

Rather than talk HP and TQ, the idea is 'area under the curve'. A mild motor will 'feel' stronger than a hot mill at street speeds - simply because it was designed to make power at a lower specific speed. A RV cam is a good example; reduced overlap so as to make more TQ. You're effectively going to make a motor which makes its power between 2000-4500 RPM, with the ability to spin thru 5500 RPM with no ill effects. The shortie stroke is there to minimize ring speed and subsequent frictional losses - while it won't thump like a stroker 350 - the mild cam will make the motor feel bigger at street speeds.

A motor set up to make some MPG will naturally feel strong at low RPM levels. As for hard numbers - figure about 1 HP per cubic inch and about 1.15 ft/lb per cubic inch with a sub 270 duration (advertised) cam, aluminum heads, 9.5:1 comp ratio, and the low friction stuff mentioned above.

 

Yeah! and a windage tray...

 

Sounds like what I need for my daily;it's only 20 yrs old so I wouldn't mind the late-model electric stuff, probably keep the TBI. Now I'm getting off the topic of old hot rods.

 

This is encouraging news. Can you expand on your engine combination (internally) and at what highway speeds this is ???

 

i have been thinking about doing a 215 buick v-8 in my essex, but have been curios about the mpg, i want to drive the wheels of fof it. i have a gas hog muscle car already.

 

When I was looking to up grade My 235/6cyl in My 57 chevy, I looked at several engine/tranny combos. I wanted power and driveablity.

I settled on the late 327 (5.3L) from a 2001 pickup with the 4 speed overdrive. With all the stock accesories. The stock 57 rear gears are 3.36 with a 26" tire. I put 3" two chamber flowmasters on it after the stock Cats. The engine has 295 rear wheel HP in the truck. That means it should have 330 or so are the flywheel. That is just about double what 350's had in the 70's and 80's from the factory.

It gets around 22 MPG (with My foot in it all the time) would probably get 26 or so if I could drive it sensibily. And will pull off 8's in the 1/8th.

I know this is not the traditional choice for a power plant, but it is not fenderless.......

 

The Pusher probably doesn't count as a hot rod weighs around 3800-400 lbs and is about as aerodynamic as a bill board.

No OD a 3.08 gear and I get consistant 20-22 MPG. Loaded or not doesn't make any difference. Of course I only got 1 carb, a vac secondary Holley. The spring doesn't let the secondaries come open 'til about 80 or so in high gear so maybe it doesn't fit the criteria carb wise either but if I'm snagging those miles in the truck anyone should be able to come close to the 25-28 mark in a light hot rod.

 

This thread is chock full of good science & suggestions. If the car body is "smooth", the tires have good contact patch "size" and the engine is sized right for daily driving, you've got a good combination.
Look for any places to improve the efficiency. Clutched or electric fans help. Right sized tube dia's on exhaust help. Engine temp control, helps. In my newer cars, synthetic oils helped. Serpentine belts are easier to turn than thicker v-belts. Turbo's and less exhaust restriction...on a smaller motor, will out do a larger normaly aspirated motor.

 

I'd like to here from more guys that have or are doing it .........

 

Would a high port velocity, small valve cylinder head help too?

 

Of course, the much-hated radial tire will help mileage......

 

On a recent three hour trip in my 55 Olds still kickin the factory 324(never been rebuilt) with a Holley 600, 700r4, and bias tires; I averaged 25mpg.

 

Out of interest my 289HP Ford engined T runs regular 12.6 quarters @ 112mph with 3.75 gears and returns a good 25mpg

Also my 56 F100 with mild 302 gets 25-26 quite easily.

We need to see good gas mileage here in the U.K. as our fuel is $9+ a gallon !!!

Steve.

 

Just occured to me that another factor to figure in is engine size to vehicle useage.

A light weight rod with a 302 Ford or a 327 Chevy or a 318 Mopar would do better between fuel ups that a big block. Big engines are overkill hen ful mileage has any importence and in a light weight car the small engine might be faster.

 

flateheadpete has said he gets 31 mpg with his peterbeater T and it's Merc/T5 combo. He has now switched to an AMC 258 I6 I think.

 

Sometimes happiness does = money. Prime example.

 

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