[TR] Fuel

[John Macartney]

There was a lot of panic in the UK in 2000 when leaded fuel finally became unavailable – except for aviation use. At the time, I was working for BMIHT at the Gaydon museum and we had a lot of dialogue not only with MG Rover Engineering Division but some of the oil companies too. While many owners of old cars had work done to their heads in fitting hardened seats (especially on the engines in Sprites/Midgets and MGB’s) a lot was made by the oil companies on what they called “lead memory”. Basically, the deposits of lead in the valve seats and immediate surrounding areas enabled cars to run happily on unleaded fuel without the need for re-seating the exhaust valves. All that many people did – and still do – was to put in a measured amount of potassium with the fuel whenever they filled up. The potassium was proved to work well as a lead substitute and many people still use it – Castrol Valvemaster being the most popular product. All in all, the European classic car motoring press made an enormous fuss and created unnecessary panic among thousands of owners about unleaded fuel when the reality was that the absence of lead didn’t really make any difference unless the engine was going to be used for racing. The further proof of this was that thousands of British sports cars were running reliably in the US without hardened seats and had been doing so for many years because unleaded fuel was widely available and being used in them in North America and had been for a considerable time. Personally, I wouldn’t worry about it unless re-seating is felt to be really necessary. The only sign of valve seat recession will show up with a feeler gauge when re-setting valve clearances. Therefore, keep an eye on those valve clearances in the early days of running unleaded without an additive. If they don’t change, you probably don’t have anything to worry about. I applied this logic to both my Triumph saloons – one with the 2.0 litre GT6 engine and the other with a TR6 type fuel injection set-up – a car that was never sold in the US. Neither engine showed any sign of valve seat recession and since selling them and staying in touch with their new owners, I understand they are performing very well and without having hardened exhaust valve seats. That was fifteen years ago!

 

Jonmac

 



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