Can some have a look at this plug.

[jet1]

Everyone has been a huge help with my piston issue so I thank you. I have been trying to source the correct plugs but have run out of time (can't get nothing up here). This is a trzix. I am trying to get a set of tr8's but don't think they will get here in time for my race(only thing even remotely close). How does this plug look?

[Tuner]

Too hot. Retard it a little and richen it up a jet or two. The little microscopic black specks on the ceramic are not your friend. You don't want to see them at all, ever, If you can avoid it.

[jet1]

Really AFR is reading 12.2! Could the plug just still be to hot. I found a set of tr8ix's in town. I will pull another degree of timing out of it though for sure.

[ParDeus]

What is total timing at now?

I agree the plug is still too hot. I'd pull 2° before going fatter. However, if it's race time, be safe and richen it. With that long at WOT, no chances should be taken.

[jet1]

Timing is at 26 deg right now. I would be down at 24 if I pull 2. Thats really getting down there. Doesn't that seem like a pretty fast combustion chamber for a as cast production GM piece?

[Tuner]

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°.

[jet1]

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°.

Oh I get what plugs I "should " have just can't get them in time up here to do so. Stuck with what i can get.

There is a very faint ring right at the bottom of the porcelin(can barely see it). Probably only a millimeter high.

Will do on the octane booster.

[Tuner]

Go up a jet size in all 4 bores, it should move the ring up a bit. That you have the ring at all is a good thing. Unless it is still too lean the cooler plugs will move the ring up some from where the ceramic joins the steel shell. For your type of severe use, I would place more weight on the plug reading than the AFR gauge. The plug is showing the actual combustion conditions which are affected by more than just the AFR, obviously, as you burned an engine down with the "correct" AFR, and it is likely if you jetted up to 11/1 it may have survived. 100LL is a blend of clean burning alkylates because (amongst many other reasons) it is intended for supercharged engines that use fuel enrichment as internal coolant in takeoff and high boost climbing conditions. You can be in the 10.x/1 AFR range at WOT and it won’t foul plugs, where other blends of fuel with high percentages of aromatics will burn sooty.

[racer189]

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]

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.

That sounds like nonsense to me. Do you know the dwell time of your ignition? People are using aftermarket engine management with the GM COP coils on blown alcohol and nitrous engines with normal electrode plugs and somehow they are muddling through it. Not surprisingly, many have better performance with the OE GM coils instead of others.

The key to using any ignition and sparkplug is the correct gap. If you notice, as plugs get colder, the gap they come out of the box with gets smaller. This is because the cold plug applications are for higher engine working pressure and require more spark gap breakdown energy. No matter what kind of ignition system, induction or CD, points or electronic, distributor or COP, the way to concentrate more energy in the plug gap is use a smaller gap, because it expends less energy breaking down the gap to initiate the spark and more energy is left over for burn duration.

I would not use more than .025” gap. If you get #9s and the come out of the box with .022, leave them alone. This would apply even if you have a CD ignition. The electrons don’t know from whence they came.

Fine wire plugs are intended for applications where burning the electrode clean is important such as for high-mileage plug change intervals, or more difficult such as a 2-stroke with oil mix in the gas.

[jet1]

Got it!!!! Thanks so much for all the wisdom here. If I win maybe I should put your guys names on the trophy

[donc]

Tuner is absolutely right. If you hook up a plug to a spark tester, or an adjustable gap tester turn on the spark looks good? Take a shop blowgun " 120 lbs?" blow across the spark , youll see what hes referring to. I know its kind of a red neck test, but its interesting.

[BrazilianZ28Camaro]

Have you access to E85?

I'm not a boat engine expert by any means , but I do know the ethanol will cool the chamber and spark plug considerably.

As you have a gas fuel system , you could blend about 40% E85 or (30% E100) with the 100LL , richen it up and let the timing where she make best power, your exaust valves will thank you.

Burning ethanol you will cool the chambers and have more octane to prevent pre ignition.

Just jet it up for best power, let it a tad rich, and forget the AFR readings, the sensors may go nuts with the mix.

[Tuner]

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%?

[BrazilianZ28Camaro]

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%?

Thats certainly a consideration, but I do believe the additional fuel volume would be around 30% with the E85 mix.