Our local MG club got a message from a former member who was packing up and moving to Florida. As all people in the antique car hobby he had accumulated a significant amount of spares and tools that he wanted to find a new home. Having just put new plugs, wires, points and condenser in the MGB I had found I no longer owned a timing light. I called the gentleman and asked if he had a timing light. He informed me that another gentleman in the club had “Claimed” everything to distribute to the club members but he would pull the timing light and any other things tuning related for me. When I went to pick up the timing light, he also had a compression gauge, an SU carburetor tuning tool and a Gunson’s “Color Tune” tuning device.
I am not a gearhead and most of what I know about mechanics I taught myself over the last three years. I have seen pages of information in early issues of the New England MG T Registry’s (NEMGTR) Sacred Octagon magazine about ignition timing including enough charts to lull the biggest gearhead to sleep. Each chart for a different octane rating. But here was this little box that consisted of basically a spark plug replacement with a glass tube that allowed you to “see” the ignition inside the cylinder. Essentially you tune the engine until the explosion inside the cylinder goes from orange (too rich) to a “Bunsen Blue”; not a “Whiteish Blue” (too lean).
Now this is the 21st century. For $100 I can by a computer-based analyzer that can tell me the day that I switched my car from 87 octane to 93 octane. What is this color tune eyeball thing? Some kind of a joke? I imagined seeing an ad for this thing in a 1960 copy of Popular Mechanics. Right next to the Johnny Atlas ad with the big brute kicking sand in the skinny kids face!
Well, thinking I’d get a laugh from my mechanic friends I showed this thing to them. To my surprise not only did they recognize it they also admitted to having used one! Apparently, this thing works! Then I thought about it, gas burners on a stove and in a gas oven are adjusted the exact same way.
I did some research and found 50+ YouTube videos on how to use it, it is still in the car parts catalogs and online forums have a bunch of threads devoted to it’s use. The only negative thing I have come across, and I must agree, having worked in the petroleum industry for 25 years, is that modern gasoline is not the same chemical soup that was gasoline from the 60’s. It still has heptanes, septanes and a cocktail of carbon atoms. But not much benzine (too carcinogenic) It has long carbon polymer chains etc. And that was before they put ethanol in it. So the question would be, is tuning to a “Bunsen Blue” color still accurate. What is a modern alternate to accurately tuning a 40 to 60 year old carburetor system?
That sounds like a good topic for a Cars and Coffee.