I've heard this from multiple people now, but I just don't buy it because nothing I have seen so far explains how it "advances" timing. Here is why I think so.
1: I don't know about the Polaris, but I went to BR9 plugs since I run at a fairly high brake mean engine pressure and wanted them to keep engine temps a little cooler from the added compression. The plugs themself are the exact same size as the BR8s. The only difference is the porcelain insulator is shorter since it is a colder plug, but the ground strap and overall length of the plug are the exact same. Where the spark is initiated is also the exact same location with both plugs.
2: Think about the purpose of advancing the timing. The idea is to initiate the spark event earlier BTDC so brake mean engine pressures will increase and since the spark is earlier the flame front from the ignited air-fuel mixture will make contact with the piston in fewer degrees ATDC.......which in turns leads to more of a driving force down upon the piston because of the more complete combustion(expansion of gases) of advancing the spark event and igniting the air/fuel mixture.......which directly turns into more power....since those gases have to go somewhere....down on to the piston ATDC. For example(random #s).....flame front hits piston at 12 degrees ATDC, advancing the timing 4 degrees, you can roughly make that 8 degrees ATDC and you have the benefit of more complete combustion of the air-fuel mixture.
This is why I don't buy milling the head/extending the plugs advances timing. Moving the plug or head(with the plug) closer to the piston on stock timing doesn't combust the air/fuel mixture any more(and maybe even less) than it does when stock. Why? Because it's more like retarding timing IN TERMS OF PERFORMANCE than advancing it. The plug will spark(while being closer to the piston) and the flame front will begin to propogate downward towards the piston. If you move the plug closer.....all you have done is shortened the time it takes for the flame front to hit the piston ATDC......you haven't elongated the time period for the air/fuel mixture to combust more completely any further which is the entire trademark of advancing the timing. Will it possibly cause the flame front to hit the piston in fewer degrees ATDC?....yes it's possible......but with even less combustion pressure, which makes it pointless. Really all you have done is increased the chance you are going to have pre-detonation.......which is why nobody else does it. People mill the head for the increased compression you gain from it, so there is some gain in doing that.
3: Extending the plugs or milling the head has NOTHING to do with advancing the timing. They are 100% mutually exclusive events and situations. By moving the plugs closer downwards in the cylinder, all you have changes is the time period it takes for the flame front to impact the piston.........without added combustion. If you want to test this out for yourself, just torque your plugs down a little less than you usually do and then try it torquing it down more than you usually do(without stripping the head obviously)............you won't see any difference in combustive efficiency.
I know.....I don't know why it has so many hits.....it's just a for sale ad....it looks and performs a little different now. :-/
