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MG MGA - Tuning with Unleaded fuel

Hi Chaps. Forgive me if this has been covered before, but I have searched the archive in vain. My question concerns tuning the carbs when using unleaded fuel. When we had leaded fuel, you could tell (roughly) that the carbs were in tune by looking at the colour of the inside of the exhaust tailpipe, and by the colour of the plugs. I've got my 1600 mkll pretty much in tune according to the Colourtune, but the tailpipe is always black inside, even after a good run, and the plugs are black too, with just slight browning of the central electrode. Is this a feature of unleaded petrol, or a sign that, despite the Colourtune, it is in fact too rich? Incidentally, my 4.2 series 1 e-type shows similar characteristics. Thanks in anticipation, Adrian B
A Bennett

Adrian It is a bit harder now with unleaded fuel but is still useful. With lead in the fuel you could put clean plugs in, take the car for a spirited drive, pull the plugs and get an idea of the mixture. With unleaded I have found doing it that way the colors on the plug are a lot harder to read, but if done over a much longer time a good result can be obtained. I had a couple of weeks ago altered the mixture on my B and last weekend went interstate to our GOF, about 400 miles. on my return I removed the plugs and found the color spot on, dark brown outer with the electrode a lighter brown. The car had returned 35 miles to the IMP gallon. I think what this means is that you can use the plug color for an overall average test bur not like in the old days of say a high speed test with a half hour flog around the block. Denis
Denis4

Denis, I need some info regarding this thread. Can you please contact me by gmail as above, when convenient.
Barry
BM Gannon

This thread was discussed between 14/09/2009 and 15/09/2009

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This thread is from the archive. The Live MG MGA BBS is active now.