Spark Plugs, Open Animal

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W5R

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What spark plug are you guys using with open animals on alky? I've been using the Autolite 3910X plug but am having to change the plug a little more often than I would like to because of the plug fouling so easily. I'd like a hotter plug. I run Klotz Nitro and methanol mix and temps usually stay right around 300 degrees. Am thinking maybe using one of the flathhead plugs like the Autolite 411 maybe but want to see some opinions on what others use
 
3924 autolite is hotter.
The 10x in my opinion is used only because it takes up more space in the combustion chamber.
It is not going to spark all 4 corners.
The 411 is a short reach plug and won't work well.
Any of the briggs recommend plugs or there cross reference should be better than the 3910x.
Then just adjust heat range up or down to suit your needs.
 
Was wondering how the autolite numbers went as far as heat range, I see what you mean thanks
 
There are a lot of reasons they make different heat range plugs. A lot of things need to be taken into consideration, chief among them, the compression ratio, second to that, I would think, is the rpm range. I don't know all the technical terms, but I'm pretty sure that the plug that works in a stock, low compression gasoline engine, would not be the ideal plug for a high compression alcohol burning engine.

Let's face it, there must be a reason spark plug companies make so many different heat range plugs. I'm not totally sure of all the reasons why, but I'll that one of them is the service each plug has to operate in. Low rpm and a lot of idling would call for one plug, high rpm and a constant load another. In my two cycle days, with the McCullough's, I ran one type and heat range of plug, and with the Rotary valve (much higher compression) I ran a much colder plug. The komet's even used a retracted gap plug. Very cold! With the McCullough's, when we ran alcohol, we ran a colder plug than when we ran gasoline.

Maybe the reason you're fouling these plugs (I think they were designed for low rpm's and light loads) is because they're so hot, you have to run a lot richer. You know, it surprises me what low CHT readings people get with alcohol. It may be that their plugs are too high a heat range and that it causes them to need a richer mixture, which holds down the heat. I don't think alcohol Burns cooler than gasoline, if it did, how could it make more horsepower?

I'm certainly no expert on four strokes, but if I was racing them, I would be investigating what the manufacturers of those spark plugs are saying.
 
Bosch Platinum 2. It has 2 electrodes. i get mine at Walmart. There are several numbers. Get them and try them, just make sure you get ones with a gasket seal instead of the taper seals. Do you buy your fuel as a pre-mix? What % of Nitro are you using?
 
callen said:
Bosch Platinum 2. It has 2 electrodes. i get mine at Walmart. There are several numbers. Get them and try them, just make sure you get ones with a gasket seal instead of the taper seals. Do you buy your fuel as a pre-mix? What % of Nitro are you using?
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I'm wondering; if you went right to the manufacturer of the plugs and told them what you were doing, and told them that you had a high compression alcohol burning engine that you were racing at high RPMs, what plug do you suppose he would recommend, and I wonder if Kmart would even carry that particular plug in stock? When I was racing two cycles, the plugs I used were never available at the local auto parts store, let alone Kmart, which wasn't here anyway, I had to order them from a distributor.
 
Here's what you might try.
Denso Q16RZU11 hot plug , Q20RZU11. Medium
Or the 22 cold.
Autolite 3924
Ngk. Bkr5e
The denso plugs are nice fine tip
Iridium plugs may need to order them.
 
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You guys do realize that the spark only goes to one electrode don't you? The spark goes to the one with the least electrical resistance. The extra 1, 2 or 3 electrodes don't do anything except take up space.
However if the path to the first side electrode deteriorates and causes an increase in resistance the spark will the go to the next electrode with the least resistance. The question becomes how many people leave a spark plug in a kart racing motor until it actually wears out. I'd venture to say, not very many. The spugs get changed all the time whether it's needed or not.
 
I do for one.
Tried a pair or three prong plugs out of a RX7 wankel in my 69 triumph would not even start till I put the NGK plugs back in.
Knew then and there that the split fire plugs were all hype.
The old champion spark plug cleaner and tester showed some interesting things as well.
 
callen said:
Bosch Platinum 2. It has 2 electrodes. i get mine at Walmart. There are several numbers. Get them and try them, just make sure you get ones with a gasket seal instead of the taper seals. Do you buy your fuel as a pre-mix? What % of Nitro are you using?
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10:1 Klotz to M5 is how I mix it. It is not the same as nitromethane
 
Flattop gave a variety of good choices. I really like the Denso plugs we also stock and sell them, although you may or may not find them at your local Walmart or auto parts store - I have no idea if they stock them. The problem with the fine wire plugs is that they foul even easier. If you find that you're fouling plugs...my thinking is that your problem is not with the spark plug heat range, it's with your carb tune (or you're simply letting it idle on the grid too long.) This has always been a problem with bigger Tilly's drilled with a very rich pattern for low rpm and a reason why I like using the Mikuni accelerator pump carbs instead.
My experience has always shown me that the higher the compression, the colder the plug that needs to be used. It would seem to me that you're wanting a hotter plug thinking that it will better burn a too rich condition that is fouling your current plug. A hotter coil, with more voltage at the plug gap, would make more sense to me.

The 3910X is a fine plug for a stock class application where you are simply trying to displace the volume in the combustion chamber. Don't believe the hype of having several (more than one) ground straps. I do, however, like a bigger flame kernel (which also helps resist fouling.) It'll take a big charge to jump a larger gap.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
alvin l nunley said:
Just saying what you did is what's hateful. I was only making a suggestion, there was nothing hateful, either about it, or intended. And who are you, getting on my case, anyway??
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You have a cute little way of turning things around so they seem to favor your witless train of thought every time you respond. Your 'making a suggestion' had all the implications of someone telling another person that you think they are a dummy when in fact most of the time you are the dummy.... As for who I am, I'm the person that is going to point it out every time I see one of your belittling, condescending responses. Maybe if I do it enough, you will wise up and start responding with a little more respect for the questions and questioner.
 
"Maybe" silverback was referring to tecbigdog. "Maybe" silverback was taking up for you. "Maybe" you owe someone an apology and "maybe" not!
 
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