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 Timing issues 
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Joined: Mon Jan 27, 2014 4:31 pm
Posts: 39
Has anyone seen a deterioration in pump fuel this year. I've never had a pinging problem with my car. My timing was optimized for my car. Last year I could pull a grade with a heat soaked engine usually with no problem. If it was very hot, in the 90's I would have to go up to 91 octane. My combination is a 406 sbc with 190 AFR heads 10.25-1. Cam is 222-230@.050. 200-4r overdrive with 3.42 gears. The motor usually runs at 190 degrees.


Thu Jul 21, 2016 11:38 am
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
To me, it seems different with every new tank of fuel. I occasionally get fuel that apparently has higher % ethanol in it that makes the '72 318 2bbl (1/2 ton PU) run just a little too lean and have a very slight uneven miss on level ground at 30-40 MPH. Once in a while some fuel will ping, though it isn't clear that the higher % of ethanol is involved in that, it will ping with either slight surge or no surge fuel. Erratic fuel is the reason many old cars, such as Model T and Model A Ford, had the spark advance in total control of the driver with a lever at the steering wheel.

If you are having trouble with detonation try adding an Octane booster that contains MMT. See that it says "Contains MMT" (Methylcyclopentadienyl Manganese Tricarbonyl) somewhere on the label ........ It may not need as much as the instructions say to use if the pinging problem isn't too bad.


Thu Jul 21, 2016 8:27 pm
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Joined: Sun May 12, 2013 5:21 am
Posts: 332
Location: Michigan
I've always herd to try and use the same station to be consistent, I think tuners right and some have a lot more than 10% ethanol.

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Thu Jul 21, 2016 9:40 pm
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Joined: Mon Jan 27, 2014 4:31 pm
Posts: 39
I spoke to a person who I think is very knowledgeable about todays fuel. He said that there are three tiers of gasoline. The major company's use the top tier [Sunoco Mobil BP Shell]. They have better additives that help clean combustion chambers and help volatility; that aid vaporization. The lessor gas company's don't use as good or as much of these additives for cost cutting purposes. Now he also explained there is a difference between summer and winter grades of gas The octane is the same but the volatility is different. The volatility has an effect on the vaporization of the fuel with the summer blend being not as good. Use brand names and higher octane.


Fri Jul 22, 2016 10:20 am
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
In the last several months I have had several successive tanks of gas from the same "major" brand station that, one after another, were all different. One runs good with no slight fluff at 30 MPH and the next runs lean. The reason I notice this is the situation is unique with this '72 318, the carb is right on the lean limit at 30 MPH level road with the engine hot and the choke off, so just a little more ethanol puts it over the edge where it is a tiny bit irregular running at that light load. The successive tanks of fuel also have a noticeable difference in cold start and smoothness in the first couple of minutes, not objectionable, just different. Whatever unknown variations are affecting the basic gasoline stock from batch to batch, the amount of ethanol is not consistent. The old truck gets pretty good mileage so I see no reason to "fix it".


Fri Jul 22, 2016 12:49 pm
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