Name that tune – Gunson Colortune

I finally got a round to trying out the Gunson Colortune I got last October. It wasn’t as difficult as I thought it was going to be with the instructions in clear English and to the point. The most difficult part was putting in the spark inspection plug in, without burning my fingers on the exhaust manifolds.

On the instructions it said you only needed to use one cylinder on a single carburettor and one inlet manifold design as per my V4. It was a simple task of removing a spark plug from any one of the four cylinders and replacing it with the Gunson spark inspection plug. It advised on having a clear view as possible of the plug which would become evident later. As mentioned earlier, the awkward part was fitting the inspection plug with its copper washer as it was quite a lot shorter and stubbier than a spark plug and difficult to get a decent grip with finger tips especially with a warm/hot manifold nearby. A deep 14 mm socket would have been best to tighten the plug but finger tight with a normal socket was good enough. After that, a long thin rod from the set was screwed in place so the HT lead could be connected.

As can be seen by the video, a blue glow/flame can be seen after adjustments had been made, but earlier the colour was quite yellow/orange as the choke was out on warm up meaning the fuel/air mixture was rich. Once the engine was seemingly up to temperature with no choke I only made small adjustments (1/8th turns) of the idle and fuel mixture to get the blue colour that I was after (Bunsen Blue as per the instructions). In the kit is a long black tube, this was for any awkward positions to view the glow from the inspection plug as it had a mirror on the end to aid with the viewing options. Once I was satisfied that my minor tweaks were good, removal of the Gunson plug was a lot more tricky due to the extra heat around the plug, engine and manifolds.

Gunson Colortune as used on the Essex V4

A week later with improved weather I took the Corsair for a drive to Sturminster Newton for the Saturday once a month informal car enthusiast gathering. The engine once warm, sounded smooth and ran quite nicely which in turn made for a pleasant drive, the tune up surely having made a difference. Once parked up, the Corsair drew more attention this time than the previous occasions so it kept me occupied chatting to various people.

Classic Cars Sturminster Newton
Sturminster Newton March 2020

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