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Old 08-23-2007, 10:09 AM   #1
Adrian Chadwick
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Default Octane Requirements 1979

I don't want to open too big a can of worms here but..

My new to me 79 came with all sorts of documents and factory manual but no owner's manual.

What is the recommened octane level for the 79 L82 engine, been using high test to be safe?

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Old 08-23-2007, 11:49 AM   #2
tsker79
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Default 1979 Unleaded Fuel

According to the Owners Manual, Page 5-1, "Your gasoline engine is designed to use ONLY UNLEADED gasoline. Unleaded gasoline must be used for proper emissions control system operation." There is no mention of the octane requirement. On Page 7-2, the Compression Ratio for the L-82 engine is only 8.9 - 1. My guess is that the car would probably run on regular, but to be safe, a mid-grade or premium, would probably be better. Maybe someone more familiar with the engineering aspects of engines could shed more info on this.
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Old 08-23-2007, 12:26 PM   #3
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Your 79 will run on 87 which is regular. if it pings run the next higher octane. it can't hurt to run premium most do and the cost is less then a $1.80 more to fill the tank w/the good stuff.

Last edited by Jims79; 08-23-2007 at 12:31 PM.
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Old 08-23-2007, 03:17 PM   #4
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If I remember correctly, there was no such thing as 'super' unleaded in 1979.

Your only choice was what we now call 'regular' unleaded, or 87 octane.
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Old 08-23-2007, 03:40 PM   #5
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In '79 you could still find stations that had upwards of 100 octane (if you knew where to find them). But your '79 C3 only needs regular unleaded gas. As mentioned, if you get some pinging, adjust the advance or buy the mid-grade of gas. Premium gas in that car is a waste of money, IMO.
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Old 08-23-2007, 07:17 PM   #6
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I understand regular will work assuming stock timing..
But

What about those that have the timing advanced per the Lars Papers?
Does that make any differance?
I use premium anyway and don't mind wasting the money that way as I find many other ways to waste it on this car. lol
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Old 08-23-2007, 07:29 PM   #7
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Regular 87 octane is fine.

If it pings, you have 2 choices; retard timing or switch to higher octane.
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Old 08-23-2007, 11:48 PM   #8
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Just to help clarify.... Lars instructs us as to the BEST way to set up your engine for best performance and operation. The factories DIDN'T set them up for optimum performance for two reasons: 1) it took more time and, therefore, cost more to do; 2) retarded timing might generate less emissions, but it definitely produces less power...which translates to LOWER WARRANTY COSTS. Lars knows that your engine can operate properly (better, IMO) when mechanical advace is set to 34-36 degrees max and when it all comes in around 2500-2800 rpm. The engine is designed to handle that and not ping. GM didn't go to that trouble. I just had Lars redo my carb and distributor for my '71 [low compression] engine. It never ran better since I've had it, it doesn't ping on regular gas and it is more economical than before. What's not to love?
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Old 08-24-2007, 01:53 AM   #9
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My 80 was to run on 87, but I rarely did. My crate is also to run on 87. Ive only put 87 in once and didnt think it was worth the risk. When fuel is in the $3 range, what is another 20 cents....

Just my opinion
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Old 08-24-2007, 11:06 AM   #10
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Quote:
Originally Posted by Adrian Chadwick View Post
...My new to me 79 came with all sorts of documents and factory manual but no owner's manual.
Order a reproduction owner's manual or shop for an original on eBay. All Corvettes love 97 or higher octane, but they'll run on the lower grades.

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Old 08-24-2007, 11:37 AM   #11
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Higher octane = higher horsepower = better power performance = more $$$. Higher octane will not hurt the car (other than you will wear the engine out sooner). Lower octane will not hurt the car as long as it is not pinging. Use whichever you like for your "reasons".
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Old 08-24-2007, 11:56 AM   #12
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Is this the same for a 77 with an L82????
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Old 08-24-2007, 12:03 PM   #13
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Quote:
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Is this the same for a 77 with an L82????
Yep. My '80 L-82 likes 97 octane (so does my '68), but she runs fine on 87.

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Old 08-24-2007, 02:36 PM   #14
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Run the lowest octane gas that doesnt allow detonation (ping) anything more doesnt improve performance and just spends your money.

If you modify the engine, the same holds true...higher compression - more advance - run whichever octane eliminates ping..(probably a higher grade)..but dont run any more than you need...thats just money down the t*let.

no harm will come to your engine if you run higher than necessary octane, but all things being equal, higher octane will not improve performance unless you need it.
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Old 08-24-2007, 05:30 PM   #15
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Quote:
Originally Posted by 7T1vette View Post
Higher octane = higher horsepower = better power performance = more $$$.

I can't believe that this myth is still around.
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Old 08-24-2007, 05:32 PM   #16
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Quote:
Originally Posted by 7T1vette View Post
In '79 you could still find stations that had upwards of 100 octane
But that was LEADED gas, not unleaded. Leaded gas in a catalytic converter car was certain death.
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Old 08-25-2007, 12:46 AM   #17
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Mike,

1) Please explain how a higher octane fuel..with better burn characteristics...would NOT generate more power out of an engine.

2) There were lots of (older) C3 cars that didn't have catalytic converters in 1979. The statement made above was that no such "hi-test" gas was available in '79. Not true.
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Old 08-25-2007, 01:01 PM   #18
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Quote:
Originally Posted by 7T1vette View Post
Mike,

1) Please explain how a higher octane fuel..with better burn characteristics...would NOT generate more power out of an engine.

2) There were lots of (older) C3 cars that didn't have catalytic converters in 1979. The statement made above was that no such "hi-test" gas was available in '79. Not true.
1) Do some basic research yourself. I've put some easy to find links below. High octane gas is 'regular' gas with additives (in the old days tetra-ethyl lead or TEL) that INHIBIT the spontaneous combustion of the gasoline ie- pinging, knocking etc. There are no other processes or ingredients that would increase the BTU content of the gasoline that would produce 'more power'. In an esoteric sense a given volume of regular gas potentially has more 'energy' than an identical volume of high octane. In practice, this difference is not noticeable.

http://en.wikipedia.org/wiki/Octane_rating

http://chemistry.about.com/gi/dynami...tos/octane.htm

The availability of high octane gas allows either OEMs or home builders to configure engines with higher compression ratios, more adventurous ignition maps and/or cam characteristics. It is these features in the engine that produce the increased power, not the gas itself.

2) Please re-read my post. I said no super UNLEADED gas in 1979. There was plenty of leaded super gas available, as well as regular leaded. If you had super unleaded available in your area, that's nice. None was available here.
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Old 08-26-2007, 07:38 AM   #19
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There was unleaded (regular), low-lead, and leaded. Sunoco 260 was 103 octane and leaded.
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Old 08-26-2007, 12:28 PM   #20
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Paul,

Do you remember when hi-octane unleaded gas became widely available? I'm thinking mid-late 80s?
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Old 08-26-2007, 12:28 PM
 
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