Splitfires = Marketing.......don't bother

 

Exactly. Found the same to be true when I was racing as well. I was fortunate enough to find this out on a dyno rather than the track. Splitfires are junk.

 

I saw a pic somewhere that showed a used splitfire plug, one piece of the electrode broke off and wedged between the valve and valve seat. Also showed the valve and the broken piece, you could see the impression on the valve sealing surface.

 

from the pic your plugs look good

 

There was a story about the direction of the plug fire how well the engine will run. They do make the triple electro plugs also. Use in airplanes

 

Remember, electricity is going to follow the path of least resistance. It doesn't matter that the end of the electrode is split or not. Great marketing gimmick, but so were the traveling medicine shows. Just use the stock plug HD recommends for the bike unless you've built up some killer motor, then use the right heat range for whatever compression you built.

 

+1. Same thing with the Bosch +4's. One electrode is going to wear out. Whichever is the path of least resistance. It's all marketing.

NGK and Autolite have been proven quality plugs in all ICE applications for many years. And they can be had on the cheap.

 

The FTC (Federal Trade Commission) cracked down on the company who makes Splitfire way back in the 90s, due to unsubstantiated claims, they could no longer advertise better mileage, performance and longer life. A new sucker is born every day.

 

I think what you are referring to is called "indexing". It's when you put a line on the external porcelain body of the plug that lines up with the tang on the business end. When you install the plug, ensure that line is pointing up at you after tightening. This in effect, puts the tang towards the head away from the piston. In my own worthless opinion, indexing is a waste of time. Especially when it comes to what all of us are doing. Smokey Yunick once said; You can spend your time indexing plugs, I'll drink beer".

 

Actully we used to do this on our racing go karts but the idea is to use different thickness brass washers so when the plug is properly torqued the matal curve of the tang is toward the intake valve, that way any glowing chunk of crap on the end of the tang is away from the inrushing air/fuel mixture reducing pre-ignition.