Spark Plugs

BIGOL880

Member
I have 880 Oliver that I am running a 386 plug with a .35 gap. My engine builder never really gave me a straight answer on what the best plug to run is. Its bore and stroked with a 12:1 compression, electronic ignition, hot coil and 7mm wires. I think the 386 plug would have been for a points set up? Any help would be great. Thanks!!!
 
beware of the compression blowing that candle out when opening the gap . it's a lot harder for a spark to happen at high pressure than low . I also like the 386 and autolite 3116 .
 
I was thinking I might be blowing the spark out when I was gapping them at .040? I might back it down to .030. I read that the 3116 is a med-hot plug and the 386 is a colder plug? My motor guy said run a cold plug? I wanted to try the 3116 though.. any thoughts. thanks.
 
(quoted from post at 08:20:33 02/19/16) I was thinking I might be blowing the spark out when I was gapping them at .040? I might back it down to .030. I read that the 3116 is a med-hot plug and the 386 is a colder plug? My motor guy said run a cold plug? I wanted to try the 3116 though.. any thoughts. thanks.

I am sure your motor guy advised to run a colder plug, the question is how much colder. Typically this question is answered by "reading the plugs" after the pull. You will need to shut off the tractor immediately after the pull without idling back to the pits. Since the compression has been increased it is reasonable to think a colder plug may be required.

However, if you are having problems with mis-firing you may be running too cold of plugs. My NGK (sorry my Autolite catalog is MIA) catalog provides a chart of optimum spark plug tip temperature. The optimum operating range begins at 500 degrees C, the self cleaning temperature line and ends at 850 degrees, prior to the pre-ignition region.

Most of the spark plug catalogs have similar charts and some have pictures showing how the plugs should look. Your "motor guy" should be able to read them and advise you.
 

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