Re: IML: 100 Octane Gas in My 1968

["Frederick Joslin" <fljoslin@xxxxxxxx>]

The 10.1 : 1 compression ratio of the old 440s and 383s is only true with really good rings. As soon at the rings wear, some of the sealing is lost and the pressure in the cylinders comes down. I would not use any better gas that warranted by pre-detonation and you can work some pre-detonation out with timing adjustments.

----- Original Message -----
From: randalpark@xxxxxxx
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: Re: IML: 100 Octane Gas in My 1968
Date: Sun, 08 Oct 2006 11:04:24 -0400

The car should run better on it. By better, I am suggesting that it might be a little bit smoother, and responsive. The difference would be subtle, and not necessarily noticable except on a longer drive. Two things come to my mind as to why there would be little or no difference. The first is that maybe the gas isn't really what they say it is, or has been misrepresented somehow. The second would be that your car may have been "detuned" or modified by a previous owner to compensate for the lower octane/lead fuels that have been on the market for the majority of your car's life. Detuning would mostly be adjustments to the timing, point gap, plug gap, etc. while mechanical modifications could have been made to reduce compression ratio. The non-stock ignition system installed on the car may have included other adjustments to maximize performance under current conditions at the time the change was made. 

 

Paul W.

 

 
-----Original Message-----
From: Crestonave@xxxxxxx
To: mailing-list@xxxxxxxxxxxxxxxx
Sent: Sun, 8 Oct 2006 5:49 AM
Subject: IML: 100 Octane Gas in My 1968

I found a local Coastal that sells 100 octane gas for 5.99/gal. Even though it's awfully expensive I decided to give it a shot. This past summer I pretty much alternated between 93 octane and the 100 octane - in other words, when I was down to 1/2 a tank I'd fill up with either the 93 or the 100, depending on what I had filled up with the last time.

 

I didn't notice any particular improvement in the performance of the car, so I am wondering if there was any benefit to using the 100 octane, or did I just waste my money? When I bought the car four years ago I had the points replaced with electronic ignition. I put very few miles on the car each year. I do get it up to highway speeds fairly frequently when I do use it. I also use a lead substitute every other tankful.

 

Thoughts, comments, suggestions?

 

Thanks

Tom

68 Imp Convert

60 NYer Coupe

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Fred Joslin