430 Gas Mileage

[55PackardGuy]

I received such a nice response on the Packard site from Centurion that I thought I'd make a post here. This regards something that is often looked at with skeptical eyes, because it is the source of lots of hokum and hearsay, but it is a personal experience with a Buick that was in my family for years.

It was a 1969 Electra 225 4door hardtop. (Incidentally, a beautiful car to start with and nicely appointed with light yellow exterior, WHITE vinyl top--as opposed to the more common black--tan vinyl seats that were extremely soft and comfortable, even in cold weather and never seemed to wear, power seat, AC, power windows/locks, FM radio, etc.

Besides being a heavy, comfortable, stable and surprisingly agile car, it was also unbelievably economical. It had the 430 4bbl setup and consistently got WELL over 20 mpg on the highway, with up to 24 mpg that I measured on straight freeway driving. There were no modifications to this car. It even had bias ply tires. And NO cruise control.

Considering the weight and aerodynamic drag of this car, the engine must have run extremely efficiently at road speeds to achieve this kind of gas mileage. (The speedometer was accurate, too.)

I remember looking through a Chilton shop manual years ago that covered several late sixties Buick models, and finding that the '69 carb was set to run leaner than previous years or later years. It said that this was an emmissions rather than an economy measure.

Is anyone familiar with this difference? I may be recalling incorrectly or have misread it at the time, but I DO know the car got phenomenal mileage.

It was a very high compression engine (10.5 or 11 to 1, I believe) and it did "ping" under load as though it was running quite lean. This was on leaded "high octane" gas of the late 70s.

The engine never seemed to suffer any ill effects from this lean running condition, giving over 200,000 miles of reliable service. It was still running well and had never been torn down when the car was "retired."

(By comparison, I had a '65 Electra with the 401 "445 Wildcat" "nailhead" engine, and it never got over 13 mpg on the road.)

Was this '69 a "fluke" or have others had this same experience with that model or other years with the 430?

I don't want anyone to think this is one of those speculations about a "super secret carb" or anything, but was there a difference in the '69 model's carb?

[Centurion]

Guy, while not a direct answer to your specific question, I have a friend with a 1970 Electra 225 4-door hardtop (with the new for '70 455 engine) who reports a consistent 20-mpg on the highway, so some of these large Buicks delivered quite impressive fuel economy for their size.

Hopefully, someone having experience with a 430-equipped Buick can provide a more direct answer for you.

[AK Buickman]

My experience driving 430 powered Electras was the same- they consistently delivered gas MPG around 20 MPG on the highway. The powerful engines were just loafing at highway speeds due to the low numeric rear axle gearing that Buick equipped these cars with. Without looking at any manuals, the rear axle ratio was either 2.78:1, or 2:56:1 in these Electras.

AK Buickman, BCA #1955.......

[Guest my3buicks]

I've not seen that kind of mileage, 17 going to Flint(although we ran them pretty hard) and a couple other trips. I did do better on mileage than the Riv, GS 455 and GS 350 that I traveled with. Car is well tuned with a petronix system also. A carb rebuild is in the spring plans so that may help. 20 mpg would be nice travleing to Texas.

[56Roadmaster]

Guy,

I think the main key is the high ratio axle, since the 430 develops a significant amount of torque at the low end it does not need to rev high. I need to change the axle in my 83 Regal,which I put a 69 430 into. Unfortunately I am at ~2500RPM @ 65mph and the milage is down around 14mpg highway. I think proper RPM should be ~1800 @ 65mph in order to bring up the milage. This is on a rebuilt(to stock specs) with the addition of the GM electronic emissions controls system (carburated). I suppose I could put in a 200R4 but I like the TH 425 tranny.

[55PackardGuy]

So, it was probably those "tall" gears, in addition to the efficiency of the 430. It was a great car for trips: 500 mile cruising distance on a tank (25 gal). I drove it from Minnesota to California and back in 1978--a very nice road trip. My father repeated this trip a couple of years later. Of course, trouble-free both trips, including deserts (I went in July), snow and mountains. BTW, there were still a lot of drive-in movies those days, and this was THE car... the power reclining front bench... oh well, that doesn't have much to do with gas mileage.

[Guest Scott Marencic]

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By comparison, I had a '65 Electra with the 401 "445 Wildcat" "nailhead" engine, and it never got over 13 mpg on the road.

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I would have to wonder if something may have been out of tune on your '65, I drove my '65 Electra w/401 and 66k original miles to GS nationals in Bowling Green, KY this year from my home in PA, averaged about 18.5 for the trip (did a good bit of cruising while there!), and surpassed the 20MPG mark while on the highway.

I was amazed the milage was as good as it was, especially with the 3.07:1 axle, the motor certainly wasn't loafing along on the highway.

[Smartin]

My 71 455 ran up to 23mpg while driving to Flint this year. No major mods except exhaust system.

2.93 rear with 2500rpm and about 65mph.

I was pleasantly surprised. Quadrajet carbs will give you tremendous mileage if driven correctly. If you even think about opening up the secondaries, you can kiss your mileage goodbye.

[NTX5467]

I recall a CAR LIFE magazine road test of a '70 Chevy Nova with a 350 4bbl (QJet) engine and 3.07 or so rear axle ratio. They noted that it averaged about 22mpg on a road trip down the CA coast. This mpg was a good bit higher than you might expect, even from a 350 back then. They mentioned that at certain air flow rates through the carb's primary throttle bores, a QJet was "super efficient" at metering fuel. It was one of the first carbs to use a triple booster venturi setup. They noticed this situation on some other cars (which had QJets too), but did not mention them specifically.

With the "right" jetting for cruise economy, a higher compression ratio motor, efficient intake manifolding, AND an efficient high-turbulance combustion chamber dynamics, outstanding fuel economy can happen--especially in the 2000-2600 rpm ranges. Oh, I forgot to mention a long connecting rod as a possible factor too as the dwell time at TDC is greater than with a shorter connecting rod.

As for the exhaust pipe situation, I recall from the Buick engine performance seminar in Flint, that when the exhaust duration was lengthened by about 20 degrees on the GS spec motors, more power happened. This might make me suspect the exhaust duration of the stock camshafts might be a little short for what the engine "wants" or perhaps the exhaust port might be a little too restrictive (as cast). Adding a low restriction dual exhaust might appease that situation somewhat and add more efficiency at cruise than might be expected. Sounds like it might be cost effective too.

Just some thoughts . . .

NTX5467

[Guest sintid58]

While in college I had a friend that lived in Rochester Mn (about a 250 mile trip). I owned a 69 Electra 4 door hardtop and drove to see her quite often. THis was before I-90 was complete and there was quite a bit of 2 lane. I frequently saw 20 to 21 miles to a gallon on this trip and that was often at more than 80 miles an hour. Another friend of mine at the time had a 69 Chevelle with a 307 in it and he never could get better mileage on that long trip than I could. Of course my car was much more popular to make the trip in because of the comfort and ride.

[55PackardGuy]

Isn't it interesting how a smaller engine in a lighter car (307 in a Chevelle) is sometimes less efficient than a much larger displacement engine in a heavy car? It was interesting to see the responses to this gas mileage post, because it appears that some combinations just plain work better, regardless of engine displacement and weight of car. All I can say for sure is that there are many Buicks of the sixties and early seventies that were remarkably efficient given the amount of metal they were toting around. And then there were some that weren't so hot (my '65 Electra with 401, as I mentioned--and I tried tuning it every-which-way--stubbornly refused to get much over 13 mpg). The ones that did get the mileage seemed to have just the right combination of engine design, carb, and gearing to give them a broad "sweet spot" of peak efficiency while touring.

There's one thing I would bet on: when those old carbs were set up and working right, they could do a more efficient job of metering fuel and mixing it with air than fuel injection does. I think fuel injection systems overall, on average, are more efficient because they stay "in tune" more of the time than the average carb, but the carb still has the greatest potential for ultimate efficiency.

Thanks to all who contributed experiences... and Happy Holidays!

[BqUICK]

Hi,

I own a 1969 Buick Electra 225 Custom Convertible. It is fully loaded including A/C. It has a GVW of 4,700lbs. I ran a series of mileage tests int he early 90's covering over 15,000 miles and several months. Her configuration has been mildly updated more recently as described on my link below:

21 mpg on race gas

19 - 20 mpg on 93 Octane

Mid 15 sec. @ 90mph

Top Speed 130+

Original unrebuilt 430, dual exhaust, & 2.56 non-positive traction rear.

Here are some explanations that may help:

* The quadrajet carb was more efficient AND consistent than most other carbs.

* The late 60's Buick 400/430/455 series engine was more modern than 50's designed Hemi, LS-6, and W-30.

* The new "crank stiffened thin web design" design allowed the block to weigh as much as the aluminum Z-L1

* When more power can be made with less cubes, the act is more efficient

You will see this car on page two of my posting. It was used to help prototype my current Electra GSX project car called "Faithful Pursuit".

http://www.aaca.org/ubbthreads/showflat....;o=&fpart=1

Happy New Year!!!

[Guest Reatta1]

Packardguy,

I owned a 1970 Estate Wagon that consistently got 20+ mpg on the highway and mid teens in town. Also back in 1960 I had a 57 special 2 dr hdtp with the 401.

My dad asked me why I was driving such a gas guzzler. He was quite surprised to find out my 'gas guzzler' got better mileage than his Chevrolet. That car got between 19 and 21 mpg on the highway. Most of the Buicks I've had over the years have been pretty good on gas. It's only one of the reasons I've chosen to drive Buicks all these years. Good solid, heavy, comfortable cars with plenty of power and decent gas mileage too.

[55PackardGuy]

Yeah, Reatta 1, I used to refer to that '69 Electra as the world's biggest economy car! A good 500-mile cruising range on trips, too. BqUICK noted the terrific power-to-weight ratio of these engines, which some people still insist on calling "boat anchors." You want a "boat anchor" look at the power-to-weight ratio of a 350 sbc! My dad got so sick of the periodic breakage of the 454 big-block on our '74 3/4-ton pickup that he swapped in a 430. The front end road so high we had to hang the spare tire up there to level out the truck... better economy and no sacrifice in power! I wonder why GM doesn't take these engine-building techniques into the 21st century where they belong? They were truly designs ahead of their time.

BqUICK, thanks for the pictures of the '69... it's still my favorite body style. Ours did not have dual exhaust. I thought it was one of the pretties paint schemes of all--light yellow with a WHITE vinyl top. I have yet to see one exactly like it. All seem to have the black top with the yellow body. Tan leather-like vinyl inside that never showed the least bit of wear.

Good luck on Faithful Pursuit, it's a great idea. The Electra is probably the only big car that handled well enough to pull this off. By the way, at first I thought "screw the back seat," but then I reconsidered. Basically, you can give three people amusement-park quality thrill rides for the cost of the gas! Probably as safe as most of those rides, too.

[Guest]

I wil try this again, I had a 1969 LaSabre 400 with the 350 4 barrel duel exhaust. It got terrible milage and this was during the 74 fuel shortage and I drove 100 miles oneway to work. I obtained a two barrel manifold and carb at the junk yard for 10. It instantly raised the milage to the 20-23 range that you talk about. I sold it to buy a new 1975 top of the line Plymouth Valiant and remember raising hell with the dealer because the 6 in the valiant couldn't pull a sick whore off a toliet and never got better then 18 mpg