Logo
FULL SITE MENU

Help with leaded or unleaded fuel

M

mike12

New member
i have 1 1978 omc stringer 400

i have 1 1978 omc stringer 400 i/o bought a service manual for it because it has a leak in the lower unit now in the service manual it says i shoulb be using leaded fuel but the last owners used unleaded which should i use and which is right
 
"Lead was used in gas to cushi

"Lead was used in gas to cushion the exhaust valve seat in older gasoline engines that didn't have hardened seats, go to a boat shop and get some Valve Tec to add to your gas."
 
"maybe he could get some lead

"maybe he could get some lead at a scrapyard, and grind it up real fine. add it to the tank. after all, the manual says leaded fuel. even though it was printed 30 years ago, and leaded fuel doesn't exist anymore. or, if your willing to live on the edge, just run regular gas and add nothing. (just kidding, regular unleaded will be fine)"
 
"didn't Nascar just switch

"didn't Nascar just switch to unleaded race fuel this year?....as frightening a thought as it is... I think they still make some limited quantities of gas with lead in it.... I use a "lead substitute" in my 1964 Volvo V8, but any engine made after 1973 would have the valve seats hardened to deal with no-lead fuels."
 
"Leaded fuel helped reduce pin

"Leaded fuel helped reduce pinging. If unsure, run premium 93 octane (if you can afford it!) and add some lead substitute like Hy Stat does, if you hear pinging, turn the timing down a degree or 2 until it stops. I have a 1973 360 Plymouth engine in a 1980 Ford truck! Always used unleaded and still runs fine going on over 11 years."
 
"Lead does nothing to reduce p

"Lead does nothing to reduce pinging. It was used as a lubricant and coolant for the valve seats. Pinging or pre-detonation is a different condition.
If you are pinging, you can add octane boost (103 octane boost is one brand that works well) or buy premium gas. If premium is not available (and it is not available on the water where I am), most marine engine manufacturers recommend retarding ignition timing a couple of degrees."
 
"will post this and maybe answ

"will post this and maybe answer all the leaded-unleaded questions. Interesting to read anyway.

Why was lead added to gasoline?

In order to suppress the knocking tendency, there are many options and compounds to choose, but from non oxygenate groups, the tetraethyl lead was found to be relatively inexpensive and simple compound as an anti knocking agent and was widely used giving rise to ‘leaded gasoline’. Evidently, in order to obtain the given octane rating of gasoline, different quantity of lead additives were mixed with ‘pure gasoline’ depending upon the ‘source’ of gasoline obtained. The mixture known as gasoline, when used in high compression internal combustion engines, has a tendency to ignite early (pre-ignition or detonation) causing a damaging "engine knocking" (also called "pinging" or "pinking") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo in England and Thomas Midgley and Thomas Boyd in the United States. The discovery that lead additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was tetra-ethyl lead.
Tetra-ethyl lead
In the U.S., where lead was blended with gasoline (primarily to boost octane levels) since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total gasoline sales and less than 2,000 tons of lead per year. From January 1, 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines until 2008[citation needed]. The ban on leaded gasoline led to thousands of tons of lead not being released in the air by automobiles. Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams.[1] [2]

A side effect of the lead additives was protection of the valve seats from erosion. Many classic cars' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "Lead substitute" products are also produced and can sometimes be found at auto parts stores.

Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates.

In some parts of South America, Asia and the Middle East, leaded gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa with effect from 1 January, 2006. A growing number of countries have drawn up plans to ban leaded gasoline in the near future.

To avoid deposits of lead inside the engine, lead scavengers are added to the gasoline together with tetra-ethyl lead. The most common ones are:

Tricresylphosphate
1,2-Dibromoethane
1,2-Dichloroethane"
 
Back
Top