Tuner wrote:Your situation is unique compared to most people’s racing experience because of the several minutes at a time you spend at WOT. I got involved in boat racing and pulling speed skiers 40 years ago so it seems normal to me that an engine must be adjusted different for an endurance race boat than the same engine in a drag race or roundy-round car.
How many pistons will ventilate and how many times can you see people say to use a #9 heat range before you decide a #7 is too hot? Furthermore, get off the fine wire fancy metal electrode bandwagon before it strikes again.
Is a flame arrestor or something rattling around on the top of the carb and knocking little flecks of material off the air cleaner mounting flange, or is something like that making some micro-dust of metal in the intake air?
Your picture doesn’t show down to the bottom of the ceramic. Can you see a distinct grey or black ring on the insulator with a clean area below it?
If you run a too-hot plug you will have to jet rich enough and retard the timing, do whatever it takes, to keep it from getting so hot as to start preignition again. You see what that leads to.
Use a MMT octane booster in your 100LL in a ratio of 1 oz. to 5 gallons. I use a 12-14 oz. bottle to a 55 (US) gallon drum of 100LL. When you go to get the #8 plugs, check the octane boosters at the store and see which ones are labled "Contains MMT (methylcyclopentadienyl manganese tricarbonyl)" and use it. MMT raises the octane of 100LL several whole numbers. It will impart a tan orange-brown color to the plug ceramic. Too much will look like a wet brick. If the plug is too hot and there is too much MMT it will look like a shiny glazed wet brick.
With the cooler plugs, 26° should be OK, compromise, 25°.
Tuner wrote:Furthermore, get off the fine wire fancy metal electrode bandwagon before it strikes again.
racer189 wrote:Tuner wrote:Furthermore, get off the fine wire fancy metal electrode bandwagon before it strikes again.
The only reason we're trying to stick with fine wire plugs is we have to stay with the stock COP ignition (rules) and we were told by a NGK tech that the stock GM COP (510C GM # 12570616 - same as stock LSA and LS9) coils don't have a sufficient Duty cycle to power a standard sized electrode plug for extended periods at 5800 - 6000 rpm, if this is incorrect we would gladly use a standard electrode plug. Can anyone confirm or deny this? Again, your help is appreciated.
Tuner wrote:That would be nice but these guys are probably burning 40-50 gallons of fuel an hour and the boat may hold that much or more. Where are they going to put another 50%?