View Full Version : Fuel
08-11-2007, 02:48 PM
I have a few machines that use petrol (gas) it is mostly unleaded in the UK now. Are there any lead additives I could use on the older petrol engines?
Here in USA years ago when they went to all unleaded there was some additives on the market to add to the fuel but don,t know the name of it or if it,s available anymore. The claim was the unleaded was bad on the older valves & seats I believe the story was.Maybe someone on here might have more info. if it,s sold over here yet.
08-11-2007, 08:32 PM
I am not a mechanic, but as I understand the situation, if you are using very old engines like a Thirty or Sixty, the speed/compression (?) is so low that it makes no difference whether the gas is leaded or not. Perhaps someone else can correct or clarify. GWH
As I understand it, the lead in the gas causes an improved heat transfer from the valve to the seat which is cooled as part of the head, of course. If the valve overheats and burns, the extreme heat from the resultant leakage cauaes the valve face to furrow, then the seat goes.
The old engines were built with big cooling passages, pumps and radiators and were never intended to be run hotter than 212 F. boiling point and usually much lower. Few had pressurized systems. To get them hot you had to really work them--hard and constant.
Just how hard do you plan to work your relics? I have old JD all-fuel engines that never get additive and they do just fine WORKING!! I have broken heads on them but that was burning stove oil. (#2 I believe they call it now).
The only problem I have is fouled spark plugs. That's not from the lack of lead. It's because the U.S. gasoline is crap.
For a while Chevron would add a lead substitute to the fuel delivery if we wanted it. It left a thick white deposit on the plugs and made the fouling problem worse. We quit it after one delivery. I don't know what the stuff was.
I guess it comes down to your judgment. It doesn't hurt to try the stuff and if you don't like it, it probably won't hurt to quit. I think auto parts stores here still stock it but I never knew a trade name for it. A lot of the parts people confuse it with octane booster which is a different critter altogether. Watch what they try to sell you.
Snake oil sales will never completely go out of style!
08-12-2007, 06:07 AM
I always thought that running old engines on unleader could lead to valve seat failure due to the fact the engine will run slightly hotter and the lead acts as a lubricant.There were modifications to old cars to run on unleader petrol,I think the engine timing was adjusted on these older cars some years ago for unleaded fuel.I mix my own TVO fuel for my tractor.My road roller has a FORD side valve engine in it.
Thanks for your comments and observations
08-12-2007, 01:37 PM
The really old 'standard' engines will run happily on unleaded, the problems arrive when you start using unleaded in high performance engines from the 1940's through until everything was redesigned for unleaded in the '80's, for the amount of hard work you are going to give an old Ford side -valve, pottering around the parade ground, you have nothng to worry about. Unless you are running something like an MGB or Velocette for everyday use you do not need additives and probably not re-timing either.
08-13-2007, 03:25 AM
Hello Catsilver,hope you are keeping well. I see that there will be an open Day at Finning Llantrisant in September.
I have started work on the road roller,only a pin hole in the water tank and a respray left to do on it.Started preparing the 933 for its respray, the mag plays up now and again,got an idea to cure this problem .The machine runs well apart from that. I would like to get hold of a cap for this Wico mag. hard to get hold of one.
08-13-2007, 06:09 AM
Martyn, there are two bad things with the new fuels.
1. The aromatics used melt enamel paint, making it go like bubbled plastic. Not great if you have just painted / retored your machine.
2. The new fuel has limited shelf life, the aromatics evaporate out making starting difficult after 3 months. The chainsaw / mower mechanics are used to melted pistons as a result of people using "stale" new fuel.
3. The solution i have is to use avgas - used in piston engine planes it is approx 120 octane. I mix this 50 /50 with 91 octane new fuel and for the amount you use the cost is not a large factor ...but if i had a 60 or 65 ?!
Talk to the local aero club. Once you have tried it you will have it in the chainsaw, mower, its like going motor racing at the weekend - smell i mean + a grey pipe.
08-13-2007, 06:26 AM
Cat-astrophe - I don't know anything about the "new" fuel. I have heard about "ethanol". I was not aware that odors were added to gasoline. In the US, 87 octane seems to the the "standard", and in the mountains, we use 85 octane. And why would "stale" "new" gasoline burn the pistons? Inquiring minds want to know. Thanks. GWH
08-13-2007, 10:13 AM
The purpose of lead in the gas was not only for lubrication of the valve stems and to cushion the valve to seat contact, but to aid in conducting the heat from the valve to the block. In the old engines, if many of you can remember, it was common to have burnt valves in your gasoline engines. The cause of this was many but the two most common causes were from the valve being over heated from combustion. The other was that the valves and seats were not made of the quality of metal that we have used in our valves since about World War 2. Now that the lead is no longer in use, there isn't much of a threat to the post war gas engines. Especially safe from valve and seat burning are gas engines made since about 1980. Their metals are much more well addressed than the earlier valves and seats were. The first most important thing that should be done to protect your vintage engines from burnt valves is to have a proper valve grind done. A properly ground valve will have enough margin left to it's top that it will conduct eat away properly. The valve seat face will be properly lapped in to have enough contact seat area to conduct the heat away. Usually the lapped contact area should be the width of a pencil line. Read a good manual on valve grinding angles and settings and you will learn a lot more than I have the time to type out here. Old gasoline, whether leaded or unleaded, can burn holes in your pistons from pre-ignition (ping, ping, ping). Unleaded gasoline goes stale a lot quicker than leaded gas. Either dump your old gasoline, or do as I do, I cut it with fresh gasoline. From your local parts house, a gasoline additive can be added to your tanks before winter storage to help prevent your gasoline from going stale during their down time. And again, as already stated here above, if you are not working your vintage machine hard, you should not have any worries about burning your valves for lack of lead in the fuel.
08-14-2007, 07:37 AM
I drain the petrol from the tanks and always start the show season with fresh fuel on the Fordson,D2 and the road roller. On my diesel powered machines I always keep the tanks topped up to prevent condensation build up.When I first had the 933G the fuel in it was stale and smelt like varnish instead of diesel.
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