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I had never heard of ColorTune until Bill Tucker mentioned it at a Tech Session. Well a couple weeks ago Gary Brown's MGA was running really rough so he brought it over.  The first thing we did fixed the problem.  The timing was way off.  It had recently been serviced at a local shop.  In appreciation, Gary bought a ColorTune for the club.


ColorTune is a device that allows you to actually see the combustion inside the cylinder while the car is running.  The part below that looks similar to a spark plug actually replaces the spark plug.  The long thin piece screws into the top of it and the spark plug wire plugs into the top of it. 

A good air/fuel mixture will burn blue in color.  A rich mixture, too much fuel, will burn yellow and a lean mixture, not enough fuel, will burn white.  I tested it on my MGA which has two carburetors, one feeding cylinders 1 and 2 and the other feeding cylinders 3 and 4.  Since the same fuel mixture will go to the two cylinders, it is only necessary to perform this test on two cylinders. I removed the spark plug from cylinder 1 and screwed in the ColorTune spark plug.  I screwed on the long thin piece into the spark plug the plugged the #1 spark plug wire into it.  I then started the engine.
Nice blue flame
So the front carburetor was great.  I repeated the process with the ColorTune pluged into cylinder 3.  This one wasn't so good. I removed the air filter to make it easier to get at the adjuster.  It is at the very bottom of the carburetor.
While the engine was running, I screwed the adjuster, shown below, upward, reducing the fuel in the mixture until the flame turned blue.
I put the spark plug back in and took it for a drive.  What a difference. I think I could blow away Frank's C8 Corvette! Well maybe I'm exagerating a bit.  It was noticable, I'll put it that way.

So get in touch with me if you want to bring your car over and test the mixture.