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Performance Enhancements Questions on performance upgrades? Got a new performance upgrade you want to share? Maybe a nifty tip or trick to add?

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  #1  
Old 12-09-2006
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Question question about spark plug gap

Is there a difference between gapping a HD-6R12 spark plug at 0.038 and 0.043in.?
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  #2  
Old 12-09-2006
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Re: question about spark plug gap

Thanks markster 6828,thats where they are gapped at now. I will just gap the new plugs the same.
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  #3  
Old 01-11-2007
2004sportster
 
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Re: question about spark plug gap

Howdy ya'll,
Question, what are some good spark plugs to put in my 2004 XL 883 Custom?
And it does have stage 1 (if that means anything)?

Thanks
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  #4  
Old 01-13-2007
dirtrace95
 
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Re: question about spark plug gap

Just gap the plugs as to what the manual says. In some cases if you have alot of comp. and a wide gap the spark wont make it. The more cylinder pressure you have the better spark energy you need to keep the plug gap lit.
If you dont have that you will have to run "less" gap so the spark will be able make the jump. Stock parts will only support so much then you need the good stuff.
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  #5  
Old 01-13-2007
IndianOutlaw
 
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Re: question about spark plug gap

Quote:
Originally Posted by 2004sportster View Post
Howdy ya'll,
Question, what are some good spark plugs to put in my 2004 XL 883 Custom?
And it does have stage 1 (if that means anything)?

Thanks
I run NYK in everything i own (shovelhead, knuckle, 883, and all the cars and trucks)

just my preference, i can look on the shelf and tell ya which ones i run in the wifes 883, but its an 87, dont know if theyd be the same as the 04.
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  #6  
Old 01-14-2007
Street Toys
 
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Talking Re: question about spark plug gap

In my opinion it's usually best to stay with whatever sparkplugs that your original ignition was designed for. I run champions in my Harlys and Mopar, A/C delco in chevrolet and autocraft in Fords, Bosch in BMW and jap plugs in jap stuff. As far as gap is concered personally I feel I get the best results in most Harlys at around 0.40"-0.42". I think most of the time your ig. sys. will proform the best with what it was originaly designed with. I don't waste my time with the "split fire stuff "ect... I feel that all they do is take a good strong spark and turn them into two weak ones. Keep in mind though, if you put plugs in that is too "hot" it could burn holes in the top of your pistons as well.
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  #7  
Old 01-14-2007
IndianOutlaw
 
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Re: question about spark plug gap

"hotter" plugs wont burn a piston, extremely lean conditions burn pistons.

A "hotter" plug would have to function like a mini blow torch to melt thru a piston, it only sparks for a split second. Its simply a stronger hotter spark, and its been common place for years as an engine gets some age on it to step up 1 or 2 heat ranges to help avoid fouling in an engine thats starting to show some wear (i.e valve guides goin, compression loss, ect).

Infact, next time you go buy your tune up @ the local auto parts store, ask them if the plugs they just handed you are the hot ones and 90% of the time they will be, most places computers automatically give you those assuming you have hi-miles (my brother works at a nationally recognised parts store (15 yrs), and i build ALOT of engines (20+/yr) for everything from farmers pickups to 8 second drag cars)

I run hotter plugs in my junk to help with the fat mixtures i usually run, never burned a piston unless i was too far advanced in timing and runnin squeeze (NOS)
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  #8  
Old 01-14-2007
Street Toys
 
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Re: question about spark plug gap

Hello Indian Outlaw, Pleased to meet you. I din't mean to ruffle up any tail feathers or anything, I was mearly posting my opinion. You are 100% corect, increasing the heat range 1 or 2 steps in older engines usually will not hurt. However, like anything else, bigger is not allways better. If you go too hot though I asure you you will get holes in your pistons. It is definantly not a myth for I have seen it with my own eyes. I've been twisting wrenches for over 35 years as well , built more engines than I can remember, and will be attempting to break a couple of land speed records this year as well. Lucky for me I live right outside of the Bonneville salt flats. I have the only machine shop between Bonneville and Salt Lake City. I aplaud you on your 8 second dragster. that is a dificult feat to accomlpish for most people. I'm no computer "guru", I do not know how to post pictures yet by myself, when my computer buddy comes over latter then I'll show you a picture of my 8 second boat. I'll show you the plugs I'm running in it as well. They work great in the older shovelheads.
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  #9  
Old 01-14-2007
IndianOutlaw
 
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Re: question about spark plug gap

I'm not runnin an 8 second dragster, but i do build engines for a couple. Mines in the hi 11's, low 12's, but its also 4600 lbs and still a street car.

I'm sure you can melt a piston, but it'd take more than a hot plug, there'd have to be a detonation issue or a lean mixture to go with it, if not both, which is real easy to do if youre on a fresh not dialed in engine (or some of the guys ive seen that advance the ignition because it pulls harder off the line and for whatever reason ignore the sound that resembles a hand fill of ball bearings inside their engine, or "death rattle" as I call it).

I'm not ruffled by any means, just pointing out that a hotter plug by itself cant melt a piston, there has to be other things involved, usually detonation (which eats head gaskets as well) and/or way too lean (makes a hot fire, works like a blow torch in principle).

you can e-mail me those pix if ya want, its probably easier than posting here. jhtl_auto_transport@yahoo
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  #10  
Old 01-26-2007
Kong-of-WV
 
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Re: question about spark plug gap

Is a large bowl of soup hotter than a small bowl of soup? Is a long spark hotter than a short spark? Its really the same question and it really does have the same answer.

The heat range of a spark plug refers to the plugs ability to take heat from the tip and move it back in the plug to be disapated back into a cooler part of the engine or into the air. The colder the plug is the larger the contact area between the insulator and the metal jacket inside the plug will be. Hot plugs are those with small internal contact area. Heat which can not flow away from the tip is retained and so the whole thing gets hotter.

Real quick, do something for me. If you have a cold drink in front of you, if its in a can or a bottle, or a glass doesn't matter, just noticed that it is wet on the outside. Those little water dropplets on the outside of the container are made up of water the condensed because the surface of the can (or whatever) was cooler than the air in which the water molicule was suspended. The cooler the container the greater and faster water will condense on it. In a sense the same thing happens inside the combustion chamber. The colder the plug and combustion chamber walls are the more carbon will condense and stick to them. Excessively cold plugs will carbon foul.

What happens if a plug is too hot? Not much really. It will erode faster than it should and it will require more power from the coil to make it fire, but other than that it will light up the mixture just fine. The problem comes in when that plug (or anything else in the combustion chamber) remains so hot from one power stroke that it spontaniously ignites the incomming charge of the following cycle. Hot plugs are not the only thing that does this. Any hot spot in the combustion chamber can cause this problem - and the problem is called pre ignition, meaning of course that the ignition took place sooner than it was supposed to. This is not the same thing as detonation, I'll get to that in a minute. In the case of preignition what the spark plug is doing is effectively acting like a "glow plug". They just sit there red hot igniting any incomming charge without regard to electricity having been sent down the wire to them.

Cold plugs foul with carbon. Its really that simple. If a plug siphons off heat too quickly it won't remain hot enough to burn off carbon soot during normal operation. The plug soots up, quits firing, and there you have it.

Here is a concept that is easy to grasp. The more power you make with an engine the more heat you generate in the process. The more power an engine makes the the higher the combustion chamber pressure and temperature becomes. Higher combustion pressure at the plug tip requires higher voltage to get the spark to jump it. If you have an inadequate coil (not likely) or bad ignition wires or anything else that reduces power available at the plug tip the likelyhood of missing at high speed will increase.

This part is simple - the smaller the gap the less power is required to jump it. Unfortunately the smaller the gap (and spark to jump it) the less is its ability to ignite the air/fuel mixture at a rate sufficient to achieve the flame travel for which the pistor top and combustion chamber shape were designed. This ain't much though and so in general if you have to err one way or the other when gapping plugs its probably going to hurt you less to go a little tight rather than opt for the larger end of the gap spectrum.

So, here's how it all comes together. What you want in your engine is the coolest plug with the widest gap you can get that fires under all operating conditions you will encounter with your particular mix of engine and after-market parts. Different engines really do need different plugs but how can you tell whats best for your engine?

Look at your plugs every time you pull them and them get in the habit of pulling them now and then. Find out how your favorite plug manufactur numbers their plugs to denote heat range and then try one above and one below the one recommended for your engine. In general use the coldest plug that doesn't foul.

Last comment, a person would have to be an absolute fool to believe that split electrode spark plugs offer any opportunity for improved performance in any engine they might be screwed into. The split electrodes on those sorts of plugs are marketing hype at best and possibly something much worse. I am aware of one major international motor manufacturer that will void their warranty coverage of those plugs are unsed.
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