Octane Requirements 1979
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Mike,
My memory is failing me. There was a phase-in period in Canada for unleaded when leaded was still being used. There were two gas-fill nozzle sizes and you could not get the Sunoco 240 and 260 nozzles into the narrow 1979 Corvette fill tube. In fact that started in 1975 when the cat cons arrived. But the 1979s did work with 87 octane unleaded. I drove one for 17 years. You had to set the timing very carefully to avoid ping. We have to remember that the 1979 L-48 compression ratio was 8.5:1 and the "high-perfomance" L-82 was a mere 8.9:1.
When the Canadian government completely banned ethyl (lead) I simply can't remember. But I believe it was timed with the auto makers move to hardened valve seats. I can only guess at mid-1980s when MTBE was added as an octane enhancer to replace lead. That introduced a host of other emissions problems of course, in recent years with a lawsuit between Shell Canada and GM Canada.
My 1967 327/300 with a 10.25:1 CR is cranky with 89 octane but lives well with 91 and I tend to 93. But my timing is tweaked from the original factory setting. As you know the cost per liter (converted) is well over $5.00/imperial gallon now and as I am getting 14-16mpg in the city, that is my cost of driving 14 miles. I tend not to use Sunoco as all but their 94 is up to 10% ethanol and that plays havoc with rubber fuel-management components in these old cars. Newer cars with advanced polymer fittings are fine.
Sorry my memory does not serve me well.
My memory is failing me. There was a phase-in period in Canada for unleaded when leaded was still being used. There were two gas-fill nozzle sizes and you could not get the Sunoco 240 and 260 nozzles into the narrow 1979 Corvette fill tube. In fact that started in 1975 when the cat cons arrived. But the 1979s did work with 87 octane unleaded. I drove one for 17 years. You had to set the timing very carefully to avoid ping. We have to remember that the 1979 L-48 compression ratio was 8.5:1 and the "high-perfomance" L-82 was a mere 8.9:1.
When the Canadian government completely banned ethyl (lead) I simply can't remember. But I believe it was timed with the auto makers move to hardened valve seats. I can only guess at mid-1980s when MTBE was added as an octane enhancer to replace lead. That introduced a host of other emissions problems of course, in recent years with a lawsuit between Shell Canada and GM Canada.
My 1967 327/300 with a 10.25:1 CR is cranky with 89 octane but lives well with 91 and I tend to 93. But my timing is tweaked from the original factory setting. As you know the cost per liter (converted) is well over $5.00/imperial gallon now and as I am getting 14-16mpg in the city, that is my cost of driving 14 miles. I tend not to use Sunoco as all but their 94 is up to 10% ethanol and that plays havoc with rubber fuel-management components in these old cars. Newer cars with advanced polymer fittings are fine.
Sorry my memory does not serve me well.
Navigator
Joined: Aug 2007
Posts: 9
Likes: 0
From: Ohio
Fuel octane for L82
That engine does not require anything but 87 Octane. I have 11.6 compression and run on 91 to 93 octane. High octane fuel burns slower and make less power so running any higher than you need is a waste. Your stock distrubutor most likely has a very slow advance ramp up which helps on that too.
Gear ratios, and stall speeds on the converter have a great affect too.
Just trying to help.
David
A Newbee
Gear ratios, and stall speeds on the converter have a great affect too.
Just trying to help.
David
A Newbee
Pro
Joined: Apr 2007
Posts: 528
Likes: 9
From: Grand Rapids Michigan
The only exception to this is a turbocharged/supercharged car with knock sensors that will retard timing at the first hint of detonation....which would allow the car to operate under most conditions safely regardless of the octane fuel you put in, at a penalty for performance.
My 8.25 compression L48 needs nothing more than 87 octane. Nobdy can tell me that I will get more power from 93 octane. Same with our 8.9 compression L82 friend who started this post. Even though the cost difference is minimal, save the 1.80 per tank and put it in the tank for when your rear wheel bearing fail or your radiator pukes milky antifreeze all over your garage.
