Octane experts: Running a muscle car on modern pump gas?

[speeder]

Can people drive '60s domestic muscle cars with 10.5:1 CR on CA. 91 octane gas w/o problems? I see nice vintage muscle cars on the road once in a while and really wonder, particularly because I'm looking at buying one myself.

What octane was pump premium back in 1968? What octane was a Hemi or a BB 'vette supposed to run on? TIA.

[Jim Bremner]

Speeder.

I went for the same thing when I built the mustang motor 10 years ago.

If you use new modern heads you can run 10-10.5 all day long.

I wanted to build a motor to run 24/7/365 on pump 91 fuel.

Make sure that the heads and pistons do not have any sharp edges this will cause pings

Make sure that you know just what your care will weigh in at, gears, trans, tires and how you want the car to be used

The guys at comp cams took what info that I gave them and custom ground a cam for meat very little cost. I wanted the cam to come in at 3,000 rpm due to running narrow tires

I had zero gas problems with a 10.5 to one motor.

If I was going to run iron heads I would buff the poo out of the chambers or look at ceramic coatings to keep hot spots down

That and I would add in a HUGE radiator got to keep the motor 195-220 ish to prevent detonation 240 is bad

[johnco]

my 10:1 olds 394 pings sometimes under load burning regular gas. just have to back the timing up a few degrees. or you could buy lead/octane boost ever tank fill

[911boost]

My BB '68 Buick ran fine on pump gas here in CO. I just bumped the timing back a little using an inductive timing light...

Bill

[DanielDudley]

Some people also recurve the distributor, so they can keep initial advance but still have less total advance .

[onewhippedpuppy]

I'd be just as concerned about the fuel ethanol content. Nothing in that fuel system was designed for ethanol gas.

[romad]

If you are running the original heads you may run into valve seat erosion. It is highly recommended that you installed hardened valve seats. The octane even at 10:1 is not much of a concern unless you are running redline most the of the time. 98 octane is good for 10:1 at 100 vol eff., Your dynamic compression ratio under normal driving is 8:1 at best.

[BeyGon]

I ran my 71 455 Buick Skylark on 91 pump gas and only had a problem if I bought Arco gas. As long as I ran Chevron it didn't ping. It was built to run on modern pump gas and it ran fine. This was four years ago and once in awhile I would get some 100 octane for it just to try. I haven't seen any of that lately.

[Jim Bremner]

Guys with issues, what heads? Iron heads wil ping first

My 331 ford was dyno tuned, trick distributor, carb. it was a $750 tune. and I got handed a bag of take out parts. timing was 16* at start

The Corvette is 11 or 11.5 to one from the factory

[cashflyer]

This does not directly answer the OPs question, but hopefully gives some useful information.

In the earlier days of refining gasoline (the 20's), lead (specifically, Tetraethyl lead) began to be added to fuel to increase the octane. The practice became especially prominent and necessary during WW2 to allow piston engine fighter planes to develop the high horsepower needed.

After the war, the American "car craze" began. Bigger and faster were the rules of auto manufacture. And gasoline companies now knew the easiest and cheapest way to give those engines the octane they needed; TEL. This compound is the genesis of some pumps being labeled as "ethyl" in the 50's.

Of course, lead was promoted for other benefits also, such as being an anti-wear additive, an anti-knock additive, etc. Lead began to be phased-out when cars started coming with catalytic converters, as the lead would foul and clog them.

Below is an article that gives some octane numbers that were common prior to the Clean Air Act. Keep in mind that the current method of determining octane, the r+m/2 formula, did not exist back in the 60s. For that reason, it can be said that it is not a direct comparison of today's octane numbers with the octane numbers advertised by fuel companies in the 60s.


The History of Gasoline Octane

As the high compression engine era was gaining steam in Detroit during the early to mid 1950s, the need for higher octane gasolines was becoming more and more apparent. When automobile production resumed in 1946 following World War II, gasoline octanes in the United States averaged at 79 for regular and 85 for premium and those numbers climbed year after year until 1954, when premium gasolines were rated as high as 94 octane and regular at 86. Oil companies were promoting their gasolines, especially their premium grades, with claims that their fuels increased power and gas mileage while cleaning out the carburetor and other engine parts to wash away accumulated carbon and other deposits while regular usage prevented the future buildup of such. Among the additives widely promoted by leading oil companies were Texaco Sky Chief with Petrox, Super Shell with TCP, Mobilgas Special with a Double Compound ingredient and Sinclair's Power-X featuring a nickel additive.

As Detroit continued the horsepower race unabated in the mid-to-late 1950s, the oil industry responded by continuing to increase the octanes of their gasolines, and a few even went the extra mile by introducing "super-premium" fuels which were even higher in octane that the premium grades. In 1956, Sunoco introduced its "Dial A Grade" blending pumps that could dispense five different grades of gasoline, later increasing to eight, ranging from subregular Sunoco 190 to superpremium Sunoco 260. That very same year, Esso introduced a third grade of fuel called Golden Esso Extra, which came in a gold pump and had an octane rating of just over 100. That was followed in the spring of 1957 by Gulf, which introduced its super-duper Gulf Crest that was dispensed from a purple pump, and Chevron debuted its Custom Supreme grade in the western states.

By 1958, oil companies generally took a position concerning the number of gasoline grades offered with the greatest majority choosing to stick to just two (regular and premium) and simply increasing the octane ratings of both grades of gas with the premium fuels coming very close in octane to the super-premiums offered by some competitors. That year, regular gas averaged at about 90 octane and premium hit the 98-99 mark. With compression ratios on Detroit's hottest engines reaching the 10 to 1 plateau and higher, nearly half of all 1958 automobiles were powered by engines requiring premium fuel. And that included virtually all medium and higher-priced automobiles, leaving only a few lower priced cars powered by engines capable of using regular fuel including most Ramblers and Studebakers, as well as Ford, Chevrolets and Plymouths with standard six-cylinder or small V8 engines.

But the advent of smaller compact cars with more economical engines, both domestic and foreign, along with detuned engines in some larger cars, slowed down the octane race a bit and by 1961 only one-fifth of new cars were powered by engines that required premium or super-premium gasolines. Motor Trend magazine noted the trend toward economy that year by pointing out that Chrysler Corporation had reduced compression ratios across the board on standard engines to burn regular gas, a move that may reduce miles per gallon fractionally but give you more miles per dollar. "Five years ago, new car buyers swallowed premium gas as a necessary evil; today a salesman has to have a good reason for specifying it."

With a smaller proportion of new vehicles on the road requiring high-octane gasolines and the octane ratings of both regular and premium grades continuing to climb, demand for the more expensive super-premium grades, never really that high, dropped dramatically. In the fall of 1961, Esso and Gulf both discontinued their super-premium grades of fuel in favor of lower octane fuels to supplement their regular and premium offerings. Esso increase the octane of its premium Esso Extra and introduced a new middle grade of gas, Esso Plus, which was inserted in price and octane rating between Extra and their regular fuel. Gulf took a different direction by replacing its super-premium Gulf Crest with a new sub-regular product, Gulftane, which was priced about one or two cents less than its Good Gulf regular - and also designed for vehicles that could use gasolines with octane requirements lower than regular grades. In the process, Gulf created a subregular product that was priced on par with regular gasolines offered by cut-rate independent gas stations that generally sold gas for a few pennies less than major-brand stations - sparking off "gas wars" in many areas of the country where prices often dropped as low as 18 cents per gallon for regular and subregular grades (compared to the prevailing normal regular fuel price of 25-26 cents per gallon).

As the subregular and middle grades of gas came to market in 1962, the average octanes of gasolines in the U.S. now stood at 93 for regular, 99 for premium and 102 for the few super-premiums still left on the market. Those numbers would increase only slightly in the next few years to around 94 octane for regular, and 100 for premium by 1967.

By this time, other oil companies jumped on Sunoco's bandwagon by offering blending pumps dispensing several grades of gasoline from one pump to tailor fuels to a particular vehicle's octane requirement. Signal Oil Co. offered seven different grades of gasoline through its blending pumps at its Hancock and Norwalk stations in the Western United States. In the Mid-Continent region, Conoco began testing four-grade blending pumps in some markets in 1965 and introduced the concept throughout its marketing area two years later. In addition to Regular and Premium, Conoco offered its sub-regular Conotane (similar to Gulftane) and a Super grade between Regular and Premium similar to Esso Plus. A similar four-grade pump setup was offered by Skelly that included Skeltane (sub-regular), Regular, Special (intermediate) and Keotane (premium).

The development of true high-octane gasolines came to a screeching halt (along with the musclecar era) as a result of the Clean Air Act of 1970, which stipulated many federal mandates for automakers to reduce emissions of their engines. With that, General Motors President Ed Cole announced that his company's engineers found the answer to meet these ever toughening standards - a catalytic converter, which got the job done but required the use of unleaded gasoline. As a first move toward the 1975 models that would be equipped with such devices, GM reduced compression ratios on all of its 1971 engines to permit the use of low lead, regular leaded or unleaded gasolines and other automakers soon followed. This move spelled the end of the "octane race" and as unleaded gasoline was being phased in at most U.S. service stations during 1974 in time for the 1975 and later models that would require such fuels, the higher-octane premium and super-premium leaded fuels gradually disappeared from most stations - leaving only lower-octane leaded regular and unleaded grades. By the late 1970s/early 1980s, the last of the leaded premium grades disappeared as oil companies introduced new premium unleaded fuels that were higher in octane than the unleaded regular fuels (91-83 vs. 87) - but still lacked the moxie of leaded premium fuels, leaving drivers of older cars with engines requiring high-octane gasolines with few options to keep their classic rides intact without undue engine knock, creating a cottage industry for octane boosters and, with the recent phaseout of leaded gasoline altogether, additives to replace lead as a lubricant against valve recession.

[M.D. Holloway]

Originally Posted by onewhippedpuppy

I'd be just as concerned about the fuel ethanol content. Nothing in that fuel system was designed for ethanol gas.

Bingo!

[speeder]

Thanks all! Is there a percentage of ethanol in fuel, below which it might not be a problem? Does all pump gas in CA. contain ethanol? What percentage, if anyone knows?

As for the other replies, which I really appreciate, this a stock/numbers matching 1968 Olds 442 with 10.5:1 CR and original heads. I'm not interested in building a custom, modern motor for it, though I might have to remove the heads and address the valve seat issue. I may find that someone has already done it, the car is coming with no records. I like the idea of the huge radiator, though, and that is something I'd look into.

My machinist is very bullish on the idea of running it on modern pump gas, he thinks that I will have all kinds of engine issues related to fuel. He's an old guy, (semi-retired and started when he graduated from HS in 1960), but he's also a damn good engine guy with tons of experience working on street and racing motors. I can get 100 octane gas in town to blend with 91 and create whatever octane I want, but at substantial cost and inconvenience. Even if it ran well on 91, it's not exactly an economy car to start with. Obviously, it will not be a DD.

Thanks again.

[speeder]

Special thanks to cashflyer for that article!

[RANDY P]

Wait until you sit and idle at 100 degrees outside. That carb turns into a teapot. Percolation of fuel....

That's the problem...

[speeder]

Originally Posted by RANDY P

Wait until you sit and idle at 100 degrees outside. That carb turns into a teapot. Percolation of fuel....

That's the problem...

That won't happen, bro. I live in heaven, and I have lots of different cars to drive.

[RANDY P]

If they get rid of ethanol, we're set. But that's what it will take.

I'm severely limited on pump gas on my LeMans- Cam's too big for EFI, and I want the power....Stuck with a carb. Not to mention a Poncho motor isn't exactly a popular EFI target....


rjp

[speeder]

Originally Posted by RANDY P

If they get rid of ethanol, we're set. But that's what it will take.

rjp

We can only dream. Ethanol is bad on so many different levels.

[Jim Richards]

Denis, I may have missed it but did you get the 442?

[nota]

water/alcohol mix is one way
[a buddy was a salesman for mr wang the guy who did the p-51 system]
just DO NOT run out of the water/alcohol mix

e-85 ? not much gas but cooler mix turbo guys like it

alloy heads cost and no longer original

non pump grades race or avgas ? = cost

locals in south fla now have no alcohol hi test for boats at a few stations

[flipper35]

Kwik Trip sells 93 octane fuel as recreational fuel with no ethanol added. I use this in anything with a carb. Never had any issues with a 383 Coronet using it.