So what's the difference with Champion LV series spark plugs?

[1960 Starflite]

Still working on the new to me 1975, 850. Have the timing/belt thing done.

OK, my question. Going thru my repair manual I find that 1973-75 Merc 850"s used three different spark plugs. L76V, UL77V and L78V. What gives with that? They all have the same Type III ignition, same timing specs (idle and full).

I went to the Champion Spark Plug site and found an * beside these plugs, (* Surface fire plugs don't have a heat range). Sooooooooo What is the difference?

Thanks, Tom

 

[Chris1956]

Re: So what's the difference with Champion LV series spark plugs?

If you look at the L-76V and the L-78V, you will see a difference in the ground shell part of the spark plug. I have no idea what effect it has on the firing of the motor. Maybe a smaller or larger gap to bridge? I never used the UL 77V. I thought that was an OMC plug.

 

[oldman570]

Re: So what's the difference with Champion LV series spark plugs?

On the surface gap plugs the distance from the center electroid to the plug base is diffrent clearance as if setting a standard plug. The #'s are the heat range, and size, lenght of thread, of the plug. Surface gap plugs are less fouling than standard plugs as there is no electroid hanging down to sheild and foul the plug from the oil and gas being burnt. The + electrold is made of tungsten on some plugs and other metals on other plugs.