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Project Snicket, Colortune

One tool I forgot to mention in my last post about tuning, was the Gunson Colortune.

In a world where everything is digital, with sensors and readouts, it’s fun to be learning how it was all done back before all this.

The Gunson Colortune was basically an analogue, visual, Air to Fuel Ratio display. These days you would use a Lambda, or O2 sensor to detect the AFR, but they didn’t have them back then (or if they did, they must have been crazy dollars).

The Colortune is, for lack of a more technical description, a see-through spark plug.

This allows you to see into the cylinder, and see what the combustion flame looks like.

You screw it into the cylinder in place of the normal 14mm spark plug, connect an extension and connect the ignition lead to that. The kit also has a periscope sort of mirror device to make it easier to see in awkward spaces

If the cylinder is burning lean, the flame will be a pale blue/white. Like this (oops)

Perfect is a dark blue

And rich is orange

I picked up a Colortune from an awesome member of a forum I’m on, and set it up when I was changing the jet adjustment on the carb. I started with a very light blue since the mixture was very lean, and now I’m on the edge of dark blue and orange. If I lean the mixture out a little it’ll be a solid dark blue.

There is a lot that can be learned from looking at how the flame reacts to different situations. This is the instructions for the Colortune that identify what could be causing different issues

It’s a pretty cool little tool, and I will continue to use it when playing with old cars. I may even try it on Tess at some point.

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