Twenty years ago we were worried about the additives Tetra-Ethyl-Lead (TET) being removed from our petrol and the effects this would have on the exhaust valve seats of our engines. Those that were destined to suffer the worst were those cut direct into the cast iron of the cylinder head. Back then we were bait for those con-merchants trying to sell us things like packets of tin balls to drop into our fuel tanks. The claims were that this would improve the fuel’s octane rating and protect our valve seats. One claim was based on the supposed fact that in Russia in WW2 this tin additive had protected the valve seats of the Rolls Royce Merlin engines fitted to the Supermarine Spitfire. Russian petrol was awful and only about 80 octane. Well, the tin may well have upped the octane rating as I cannot disprove that, but as I have worked on Merlin and Griffon Vee 12 aero-engines (RAF Aircraft Engine Fitter) I can confirm that their cylinder heads are made of a cast magnesium alloy with hardened steel valve-seat inserts, screwed into the head. So no tin balls were needed to protect those valve seats! A diagram of the Merlin head is shown for you to study. To stop our car’s engines having their cast iron valve seats burnt away, many had the cylinder head modified with hardened steel inserts being fitted. Sometimes this was not possible and I have to put an additive into the petrol tanks of my two ancient AJS motorcycles each time I fill up. My MG YB had its head leadfree modified fifteen years ago by Ely Classics (then called Ely MG). Once the TET had been replaced with some very volatile and ecologically unfriendly chemicals, it was not long before the EU drew up a ruling that we were to remove these current additives and use an alcohol based one.
On the face of this it seemed logical, but they are using our food to produce Ethanol for adding to car petrol! In a world already short of food I find this amazing. With an alcohol you produce mostly water when it is burnt. They distill sugar cane, sugar beat, cereals and wood chippings to produce this ethanol. Currently the EU is making us add 5% of it to petrol. Soon this is to rise to 10%. You can buy quite high levels of this added to petrol at garage forecourts, and you need to look out for the ‘E’ signs; ie, E85 is a fuel that has 85% of ethanol in it. E10 has 10%. Ethanol improves the octane rating of petrol but does not protect your valve seats as TET did. TET was removed as lead levels were rising to dangerous levels in busy cities. Lead in your bodies system drives you mad! So adding ethanol seems at first sight, apart from using our food supply, not too dangerous.
BUT for those of us with older vehicles there are some very important problems that Ethanol will produce. For instance it will cause serious corrosion in metals such as aluminium, brass, copper, and steel. Our SU carburettors, electric fuel pumps and petrol tank contents sender units and made of MAZAK, a cheap alloy made up of aluminium, zinc and copper. Our fuel tanks and pipes are made of mild steel and copper. The pipe unions are made of brass as are the floats in the carburettors. Today’s cars use stainless steel pipes and connections with modern plastic items, all immune to ethanol oxidization. The main problem is that ethanol, being an alcohol, can easily absorb water. It is hydroscopic (just like our brake fluid is and why it needs changing every few years). It gets this moisture from the atmosphere around us. On damp days it will absorb quite a lot. This is no problem if you use the car often, refuel often so flushing the system through, and do not let high levels of water content accumulate. But, if you do, the petrol, ethanol and water eventually separate in the tank into three distinct layers. This would happen if you leave your car unused in a garage over the winter months. Now with just 5% ethanol things may not be too bad; 10% means you might need to fit modern fuel plastic lines that are unaffected and a nickel steel needle in the carb. Eventually we may have to have the insides of our fuel tanks and pipes internally nickel-plated. A drain down tap will be needed under each float chamber to empty the carb if the car is to be left standing for any time. The brass float will need to be replaced with a modern plastic one, hopefully people like Burlen will soon be selling us Ethanol Kits for SU equipment.
If you have an old motorcycle it is worse. Ethanol being an aggressive solvent dissolves fibre glass fuel tanks; it also dissolves the resins used to seal the insides of old leaking steel tanks. This stuff becomes a thick sticky gell and completely blocks up the carburettor. There are modern resins that can be used to replace these older ones, but the old stuff needs removing first. Older rubber ‘O’ ring seals are dissolved. Many classic motorcycle owners now drain down their fuel systems for winter storage.
Petrol you may store in cans will also eventually separate and be useless. On aircraft ‘Water Drain Checks’ are done weekly to each fuel tank as kerosine (paraffin) absorbs water like ethanol and from condensation inside the tanks. If this water is left to accumulate strange plant growths develop inside the tanks and eventually break away and block fuel lines, pumps and engine fuel filters. An aircraft with no fuel getting to its engines cannot pull into a layby to fix itself. Pure water being injected under pressure through a combustion chamber in a gas turbine puts the flame out. Water in our tanks will do the same.
The next section added 26th February, 2012.
Many will be aware of the problems of the adding of Ethanol to our petrol and its ability to ‘un-solder’ joints in fuel pipes and floats in carburetters (the Ethanol dissolves the lead and tin in the solder). The percentage of Ethanol in our fuel is about to rise from 5% to 10%. The company who now owns the SU name is Burlen Fuel Services. They are busy preparing a kit for the type of SU fitted to the MG Y Type.
Currently your SU has a brass float made of two halves, soldered together (part number WZX1303). You can now buy a composite float that is unaffected by Ethanol (part number AUE898) from them, phone number 01722 412500, cost with P&P £28.68. They are also supplying Ethanol-proof steel needles (your current ones are brass, an alloy of tin and copper) and are currently teasing out a compound to replace the cork seals on the jet tube (Ethanol dissolves the glue that binds the cork particles together).
So either you continue to use the high-priced Ethanol free ‘top grade’ petrol pump, which may not for much longer be Ethanol free; or you buy a new float before you are caught out when yours sinks….and keep your eyes open for the new seals.
Article and additional information supplied by Neil Cairns