bosch racing plug with 4 prongs


I purchased a bosch w prong racing plug the thing cost 10 bucks I am going to be trying it in a predator 212cc engine with pump gas I am wondering if anyone else has tried it and how it performs

alvin l nunley

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If it was me, I would make four test runs with the 3910 than four with my normal plug. Back and forth. This would tend to eliminate differences in the track and you're driving.
I tried a lot of different plugs in my Macs and found that the champion gold palladium was the best. One single small electrode. I forget the number but in any case you would most likely have to run a hotter plug than the Mac because it has a much higher compression. I always ran the coldest of that type, so pick one a little hotter, maybe 2 to 3 ranges higher.
Is there a heat range chart for that type plug? I'd love to see it.


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I usually used the Autolite with my clones but once I ran out of them and was having an issue with the plug and with no much time to check what it was I borrowed a Bosch that was told to be very expensive. Engine seemed to run better than ever. In the rush of packing I returned plug and forgot to ask which model it was or look myself and I was never told later when asked. Curious.