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Neighbor says 30 MPG from a 1967 427 V-8; I say boooooooogus

I don’t know how he calculates his mileage, but I’m pretty sure it must involve dividing by the cube root of wishful thinking and multiplying by the coefficient of imagination. (Avagadro’s number may be involved, but he won’t show his math)

30 mpg from any 427 V-8 is bogus, let alone a carbureted one from 1967. He says that it’s because he doesn’t have a catalytic converter. I didn’t press this too hard, because I was sure he was about to tell me that back when we had leaded gasoline he was getting 40 MPG…

Is there any chance my neighbor is in posession of something that will save the Earth and I’m just being a curmudgeonly cynic to an otherwise noble and good guy, or can I simply let out an absurdly long “boooooooooooogus” and walk away, knowing I’m not going to find any joy in this conversation?

I can imagine, with a carefully tuned high-compression 4-bbl 427 manual transmission, running premium and a ‘mileage’ rear axle in a Corvette, not going over 55-60, no traffic, just maybe. And maybe he got that on a trip from Denver to Dallas, downhill all the way…

What kind of car?

Of course it’s bogus.

In reality, this car (likely a Ford Galaxy or similar full-size Mercury) would be lucky to get 14 mpg on the highway, and ~9-10 mpg in local driving. However, rather than tell your neighbor that you are aware of the inaccuracy of his “calculations”, I would suggest that you just drop the subject and allow him to get back to the other important topics in his life–most likely things such as “The Kenyan Conspiracy” and Alien Abductions.

Gee, I thought the catalytic converter increased mileage as it aliviated the need for air pumps et al. Can a 427 get thirty miles per gallon ? Maybe as stated if the car were light, aerodynamic and geared correctly. But then, why the heck would it be worth it to have one. Aren’t they suppose to be horizontal gravity generators ? The exercise in trying to extract 30 mpg from said engine wouldn’t make it worthwhile to own one.

My neighbor has one in his speed boat. When it is running, mileage is measured in gallons per hour.

The 7.0L (427.8 CI) LS9 in the current Corvette Z06 is rated for 24 MPG highway. With the right conditions and the right driving technique, I don’t think 30 MPG would be out of the question at all. But for a 40+ year old 427 without an overdrive transmission, I would tend to doubt it.

In the right vehicle, with the right driving environment, the right hypermiling technique, and all other details optimized, I don’t think it’s impossible, but I DO think it’s unlikely. Put it in a small, light vehicle like Sunbeam Alpine properly geared and driven and it’s fiesable.

By the way, I had a colleague who had a small collection of Sunbeams, one of them a reatored Alpine with a 427. It was his daily driver. He does all the reatorations himself.

No carbureted 427, Ford or Chevy, ever saw 30mpg…Only in a laboratory test-bed type vehicle would such a thing be possible…

In the REAL world, these engines came with hot cams and low axle ratios and got 6-14 mpg.

When you buy gasoline, you are buying heat energy, BTU’s. ICE are 20 (worst) 30% (best) efficient. That means 70-80% of your money is being radiated into the air as waste heat. They would make a MUCH better furnace for your home than a power-plant for a car…

Are you kidding? Ever drive one? They made a fantastic powerplant for a car. Just not a very ECONOMICAL powerplant. Remember that none of us cared about mileage in those days.

I had a '67 Mustang, 289 V8 2bbl carb with a 3 spd stick. On the highway at 60 mph it was turning about 2,000 rpm and I’d get 25-26 mpg on expressway trips. Never got 30 mpg and I don’t believe anything with a 427 could do better than I did with that Mustang. Just someone making the good ole days a lot better than the reality of those yesteryears.

In those days radial tires were fitted to MG’s and Austin Healy 3000 MKII’s. American cars wore bias ply and at best bias belted tires. The rolling resistance of those old tires was poor. Aerodynamics of those big old cars was poor. And the 427 was a thirsty engine generally found in big cars. 30 mpg is a pipe dream.

GM’s 427 V8 was a beautiful engine…extremely powerful big-block V8.

30mph??? Downhill with a tail wind…MAYBE.

All of you are forgetting about the wonderful gasolines we had back in those days. We had Super Shell with “Platformate”, Standard Oil gasoline with “M2PG”, D-X with “Boron” and that great Blue Sunoco. All of these gasolines had secret mileage ingredients. Why, if these wonderful gasolines were available today, I’ll bet I would be getting 75 miles per gallon on my Toyota Sienna minivan.

I respect everything you’re saying, UncleT, but I still think it’s possible under the right conditions. The owner would be way out at the three sigma point of the mileage distribution curve, but I’m more willing to accept the possibility than you apparently are.

Neither of us will ever really know if it’s really true. We just disagree on whether it’s POSSIBLE!

@snafubar - so what’s the magic car’s identity?

The 427 is a torque monster. It can easily haul around a rather large car with a 2.50:1 rear axle and an overdrive transmission. Drive gently and keep the speed down and you could probably see some surprisingly high MPG numbers. I used to have a mid '80s Chevy half ton pickup with 2.73 gears and a 700R4 transmission and 350 engine with a four barrel carb. I did not have the torque converter lockup connected, which would have netted me another couple MPG. I was getting low 20s out of that truck and usually exceeding the speed limit. I always credited the mileage to the axle ratio and overdrive transmission, not the fact that there was no catalytic converter on it.

I also know a guy who had a Chevy 427 tall block from an old C60 truck in a K5 Blazer. He said the gas mileage was surprisingly good, but I don’t know the specifics.

My old 1974 Cadillac with a 500 cid V8 used to get about 8 city and 18 hwy MPG. It was barely off idle at highway speeds. I am extremely skeptical about 30 MPG from a big block.

30 seems unlikely,but an old high compression engine,pulling say 2.77 gears with pretty tall tires and a vehicle weighing under 4000 lbs without any power robbing accesories 20 + is very possible.On the other hand the best I have ever got with my 06 dakota,over inflated tires,45 mph speed limit,226 cid engine and 3.92 gears was 22mpg-Kevin

Are you sure he didn’t forget a decimal point? I remember (vaguely, this was 1971) riding with a friend in a late 60’s Bonneville- albeit pulling a boat- and getting 4 MPG. Every 80 miles, stooping for 20 gallons. Brutal.

While not a big block, I used to own a '59 Corvette with a 4-Barrel HO 283 that had a set of 4:11 gears under the rear.
At a 70 MPH cruise that car would tick off 21 MPG steady as a clock. With a set of highway friendly gears like 3.08s or 2:56s in it and some tweaking I’d like to think that car could have been bumped up to well over 25 on the road and maybe near 30.

One of my present cars has dual 4-Barrels with 3:38 gears and it also ticks off 21 MPG even with 1200 CFM of carburetion on it.
Thirty on a carbed 427 seems a stretch but I’d certainly never rule it out.

Does he tell you he’s the boss at home? If so, watch him. He’ll lie about other things. Believe about 10% of what you hear, and 25% of what you actually witness.

IIRC, 1967 was about the last year we had engines without strangulating smog controls, belt driven air pumps to pump air into the exhaust stream, and all sorts of power wasting items. That said, a '67 427 still wouldn’t get 30 MPG. I wish my Aunt Mable were still around. She’d know. She was quite a “car guy”, and bought a brand new 427 Impala. I think it was a '67, but it might have been a year or two older.

Neighbors and people at work are just great for way-out stories. The spark plugs on that thing probably never needed changing either. Oh well! File it with the rest of them. Just put er in that hand basket over there and someone will be around later to take them to fable heaven.