Originally Posted by xkazik

and if changing them with ones are good , in a good price range?

Originally Posted by wiggafly808

I got bosch double tips for $5 each.
You dont have to gap those.

Its pretty easy to install, it took me about 30 minutes, and i work slowly.

You just need a screwdriver, spark plug socket, extension, and rachet.

Originally Posted by IlyaK

There is/was a rumor out there that we shouldn't be using anything other than NGK plugs in our cars. You might want to follow that rumor dude.

Originally Posted by VIP Maxima

replaced mine with 1 step colder NGK coppers

Originally Posted by EnervinE

We know you're boosted, stop bragging

Originally Posted by 97maximaman

get over the fear of working on a car and life will treat you, you'll soon start trying more and learning more too.

Originally Posted by maximus_pr

Sparkplugs Information

How often should I replace my spark plugs? Unfortunately,there is no single answer to this question. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs.
Replacing worn out spark plugs with new ones (with sharp new edges) effectively restores the ignition system's efficiency. Misfires are reduced, power is restored, economy of operation is enhanced and emissions are reduced.
The best guide is the manufacturer's recommendation for your vehicle, as this particular service varies from brand to brand and model to model. In the absence of this information or in conjunction with it, you can rely on the advice of a mechanic who is familiar with your type of vehicle. In the best of all worlds, this would be a mechanic who is also familiar with the vehicle you own. If you find a good mechanic, whether dealer or independent, stick with him. The better he knows your personal vehicle, the better he will be able to diagnose and service it. The end result is very much like a doctor-patient relationship and, in the long run, you will have a healthier vehicle.

How much of a performance improvement can I expect from changing plugs?
A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.


What is a "fouled" spark plug?
A spark plug is considered fouled when the insulator nose at the firing tip becomes coated with a foreign substance such as fuel, oil or carbon. This coating makes it easier for the voltage to follow along the insulator nose, leach back down into the metal shell and ground out rather than bridging the gap and firing normally.

Many factors can contribute to spark plug fouling. The air/fuel ratio may be too rich as a result of incorrect carburetor adjustment or a poorly performing fuel injection system. Worn piston rings or valve seals may allow too much oil to leak into the combustion chamber, leading to oil fouling. The ignition system may not be performing properly. Prolonged idling or continuous low-speed driving may keep the spark plug from reaching its optimum operating temperature. Using too cold a spark plug can lead to the same problem. Finally, a dirty air cleaner can create a too-rich condition which can lead to fouling.

Fuel, oil and carbon fouling can all be the result of different causes but, once a spark plug is fouled, it will not provide adequate voltage to the firing tip and that cylinder will not fire properly. In many cases, the spark plug cannot be cleaned sufficiently to restore normal operation. Therefore, it is recommended that a plug be replaced once it is fouled.

Does compression ratio affect firing end temperature?
Yes, the by-product of increased compression is the elevation in cylinder temperatures. This is why it is recommended to choose a spark plug suitable for your application. NGK Spark Plugs recommends dropping heat ranges and altering Air/Fuel mixtures and timing as needed. It is very important to dissipate the excess heat from the combustion chamber in order to prevent pre-ignition.

Are special plugs always necessary on a modified engine?
It depends on the modifications. The term "modified" refers to those engines that have received bolt-on improvements that may or may not raise the engine's total compression ratio. These can include turbocharging, supercharging, nitrous oxide injection, the use of smaller-chambered cylinder heads, modified piston configurations, free-flowing cylinder heads, change of induction components and/or the use of different fuel types and octane. These kinds of modifications generally require a change from stock spark plugs.

Modifications that will typically not require specialized plugs (in most cases the factory installed plug will be more than adequate) include adding a free-flowing air filter, headers, mufflers and rear-end gears. Basically, any modification that does not alter the overall compression ratio will not usually necessitate changing plug types or heat ranges. Such minor modifications will not significantly increase the amount of heat in the combustion chamber, hence, a plug change is probably not warranted.

However, when compression is raised, along with the added power comes added heat. Since spark plugs must remove heat and a modified engine makes more heat, the spark plug must remove more heat. A colder heat range spark plug must be selected and plug gaps should be adjusted smaller to ensure proper ignitability in this denser air/fuel mixture.

Typically, for every 75-100 hp you add, you should go one step colder on the spark plug's heat range. A hotter heat range is not usually recommended except when severe oil or fuel fouling is occurring.

Does humidity affect spark plug temperature?
Yes, humidity does affect spark plug temperature. As the humidity increases, the intake air mass decreases. This results in lower combustion pressures and temperatures, causing a decrease in the spark plug's temperature.

Does ignition timing affect a spark plug's temperature?
Yes, ignition timing directly affects the firing end temperature of the spark plug. Advancing the ignition timing prolongs the time to compress the burning gases. The pre-ignition temperature also elevates gradually, since the pressure and temperature of the combustible mixture is low before ignition. Advancing your timing elevates firing end temperatures.

What is pre-ignition?
Pre-ignition is defined as the ignition of the air/fuel mixture before desired ignition timing.

What is detonation?
Detonation is a spark plugs worst enemy. It can break insulators and ground electrodes. Spark plug temperatures can reach in excess of 3000 °F.
Detonation, in simple terms, is a violent uncontrolled burn of the air/fuel mixture, which occurs when excessive heat and cylinder pressure causes the air/fuel mixture to spontaneously ignite.


Can I use platinum plugs with nitrous injection?
No, it is not suggested to use platinum plugs with nitrous oxide injection.
There have been instances where the platinum tip has lost its bond to either the center or ground electrode when they were used in a motor with nitrous.
Thus far the tech's say they have had no problems using Iridium plugs with nitrous.

Can I use Iridium plugs with nitrous injection or a blown alcohol motor?
A-. Yes, and Yes.
We double checked with the tech’s on this one, they say, while they have been watching for problems, thus far, there has been no reports of any problems in using iridium plugs with a nitrous system.
There should not be any problems using Iridium with a blown alcohol motor


I have slightly modified my motor, do I need a colder spark plug?
Possibly(more info below)

What is the torque setting for my plugs?
Plug torque settings

It is essential to tighten a spark plug to the specified turning angle or torque setting. This is for a number of reasons, over tightening can cause;
1) Damage to the threads in the cylinder head (especially aluminum heads).
2) Damage the threads of the spark plug.
3) Damage the internal seal of a spark plug allowing combustion chamber blow-by.
Under tightening of the spark plug can cause plug overheating and possibly pre-ignition. This is because one of the primary purposes of the spark plug is to remove heat from the combustion chamber, it does so by transferring that heat to the engine head. If the plug is not properly tighten it will not have sufficient contact with the head to transfer that heat. Proper tightening procedure is described below.

**Torque 14-22 ft-lb**(as per FSM)

Should I gap my Iridium Plugs?
The manufacturers say NO.
This is because most people do not know how to properly gap a spark plug, and the center electrodes on the ultra-fine iridium can easily snap if mishandled. There is no warranty for snapped center electrodes. The manufacturers say an iridium spark plug will run so much better than a traditional plug, even if it is not gapped for that motor, that they would prefer you just leave it rather than risk snapping the center electrode.
Personally, we at sparkplugs.com, gap our iridium plugs for our own vehicles (we’re rebels). If you insist on gapping your iridium plug, please refer to Proper Gapping for instruction.

How long will my iridium spark plugs last?

A traditional iridium plug such as a Denso IK20 or NGK ZFR6FIX-11 both have iridium center electrodes, however the ground electrodes are the traditional nickel construction. The ground electrode will wear out first. The manufacturers are saying 40,000 to 60,000miles on iridium plugs. But they have to temper their projections as driving conditions and motor modifications differ. Typically we have found you can expect 60,000 to 80,000 miles on an unaltered motor. (the wife’s mini-van has had the Denso's for 76,000 miles, I examined 2 of the plugs, they had some minor spooning on the ground electrode, I put them back in and will likely change them in another 5,000 miles)

Both Denso iridium racing plug and some NGK Iridium racing plugs have iridium center and a platinum ground electrodes. If installed to a regular engine they would likely last longer than most people keep their car (barring any motor problems that can cause premature plug death). But, these usually come in heat ranges too cold for an unaltered motor and are usually used in racing applications where all bets are off.

For the traditional automotive market, the longest lasting plugs are the NGK "IFR" series and the Denso "SK" series. These have Iridium center and platinum tipped ground electrodes, however these are extremely limited in application as they only manufactured these in a couple of heat range configurations.

Can old spark plugs be cleaned?
Yes, you can clean spark plugs, but in most cases its not worth it.
We do not recommend it for a number of reasons. In short, you will not get the same performance from a cleaned plug as a new plug. This is because electricity likes sharp edges to discharge from, a used plug will already have wear, and cleaning may contribute to that wear even more. (depending on the cleaning method used) If you want to try it, the below cleaning procedure was supplied to us by an old motor head. Good luck!
If the firing end is wet, make sure you clean the spark plug with a quick drying cleaner. (Examples: contact cleaner or brake cleaner).
Sand blast the spark plug using low air pressure and use a dry compound.
Completely blow all the sand from the spark plug.
Using a wire brush clean the threads and re-gap.
NOTE: Insufficient cleaning of the spark plug may lead to spark plug failure in a very short period of time. Clean the spark plug thoroughly to avoid problems later. Remember, if a spark plug is fouling it's usually a result of engine side factors or incorrect heat range selection.

Do I need to Gap my plugs?
Maybe, but likely not. Many plugs are pre-gapped for their most popular applications, however, the gap can be altered if the plug is dropped or mishandled in packing/shipping. Therefore even if the plugs are supposedly preset for your motor, it is always wise to check the gap on each plug prior to installing.It is not recommended you adjust the gap on multi-ground plugs.

What is proper spark plug gap for my motor?
.039-.043(as stated in the fsm)

What is the maximum I can open or close the gap?
Manufacturers don't recommend adjusting the spark plug gap < or > .008". The reason for this is the ground electrode and center electrode won't line up properly, hindering spark plug performance.

Proper gapping
In most cases the factory set gap should conform to your vehicle specifications. However if it is necessary to widen the gap, do so with a tool that only pulls back on the ground electrode without touching the center electrode or the porcelain. To close the gap on a plug, gently tap the plug, electrode first on a hard surface.

Heat range
The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber.

The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.

Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage

much of the info taken from http://www.sparkplugs.com and http://www.ngksparkplugs.com

The following information was added by sky jumper:

NGK plugs (according to their official product line):

V-Power Copper -- BKR5E-11 -- $1.89 ea
G-Power Platinum -- BKR5EGP -- $2.99 ea
OE Laser Platinum -- PFR5G-11 -- $9.99 ea
OE Laser Iridium -- IFR5E11 -- $9.99 ea
Iridium IX -- BKR5EIX-11 -- $6.99 ea

I believe the Iridium IX, like the G-Power, do not have the platinum tipped ground electrode or the laser welded center electrode, hence they are cheaper than the two OE laser products.

http://www.ngksparkplugs.com/part_fi...engineid=30512

http://www.ngksparkplugs.com/product...x.asp?mode=nml

Originally Posted by maximus_pr

Sparkplugs Information

How often should I replace my spark plugs? Unfortunately,there is no single answer to this question. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. As the gap between these two points grows, the voltage required to bridge the gap increases proportionately. Even the best ignition systems will be strained to supply enough voltage to completely burn the fuel. It is at this point, when fuel is being left unburned, that the time has come to change spark plugs.
Replacing worn out spark plugs with new ones (with sharp new edges) effectively restores the ignition system's efficiency. Misfires are reduced, power is restored, economy of operation is enhanced and emissions are reduced.
The best guide is the manufacturer's recommendation for your vehicle, as this particular service varies from brand to brand and model to model. In the absence of this information or in conjunction with it, you can rely on the advice of a mechanic who is familiar with your type of vehicle. In the best of all worlds, this would be a mechanic who is also familiar with the vehicle you own. If you find a good mechanic, whether dealer or independent, stick with him. The better he knows your personal vehicle, the better he will be able to diagnose and service it. The end result is very much like a doctor-patient relationship and, in the long run, you will have a healthier vehicle.

How much of a performance improvement can I expect from changing plugs?
A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.


What is a "fouled" spark plug?
A spark plug is considered fouled when the insulator nose at the firing tip becomes coated with a foreign substance such as fuel, oil or carbon. This coating makes it easier for the voltage to follow along the insulator nose, leach back down into the metal shell and ground out rather than bridging the gap and firing normally.

Many factors can contribute to spark plug fouling. The air/fuel ratio may be too rich as a result of incorrect carburetor adjustment or a poorly performing fuel injection system. Worn piston rings or valve seals may allow too much oil to leak into the combustion chamber, leading to oil fouling. The ignition system may not be performing properly. Prolonged idling or continuous low-speed driving may keep the spark plug from reaching its optimum operating temperature. Using too cold a spark plug can lead to the same problem. Finally, a dirty air cleaner can create a too-rich condition which can lead to fouling.

Fuel, oil and carbon fouling can all be the result of different causes but, once a spark plug is fouled, it will not provide adequate voltage to the firing tip and that cylinder will not fire properly. In many cases, the spark plug cannot be cleaned sufficiently to restore normal operation. Therefore, it is recommended that a plug be replaced once it is fouled.

Does compression ratio affect firing end temperature?
Yes, the by-product of increased compression is the elevation in cylinder temperatures. This is why it is recommended to choose a spark plug suitable for your application. NGK Spark Plugs recommends dropping heat ranges and altering Air/Fuel mixtures and timing as needed. It is very important to dissipate the excess heat from the combustion chamber in order to prevent pre-ignition.

Are special plugs always necessary on a modified engine?
It depends on the modifications. The term "modified" refers to those engines that have received bolt-on improvements that may or may not raise the engine's total compression ratio. These can include turbocharging, supercharging, nitrous oxide injection, the use of smaller-chambered cylinder heads, modified piston configurations, free-flowing cylinder heads, change of induction components and/or the use of different fuel types and octane. These kinds of modifications generally require a change from stock spark plugs.

Modifications that will typically not require specialized plugs (in most cases the factory installed plug will be more than adequate) include adding a free-flowing air filter, headers, mufflers and rear-end gears. Basically, any modification that does not alter the overall compression ratio will not usually necessitate changing plug types or heat ranges. Such minor modifications will not significantly increase the amount of heat in the combustion chamber, hence, a plug change is probably not warranted.

However, when compression is raised, along with the added power comes added heat. Since spark plugs must remove heat and a modified engine makes more heat, the spark plug must remove more heat. A colder heat range spark plug must be selected and plug gaps should be adjusted smaller to ensure proper ignitability in this denser air/fuel mixture.

Typically, for every 75-100 hp you add, you should go one step colder on the spark plug's heat range. A hotter heat range is not usually recommended except when severe oil or fuel fouling is occurring.

Does humidity affect spark plug temperature?
Yes, humidity does affect spark plug temperature. As the humidity increases, the intake air mass decreases. This results in lower combustion pressures and temperatures, causing a decrease in the spark plug's temperature.

Does ignition timing affect a spark plug's temperature?
Yes, ignition timing directly affects the firing end temperature of the spark plug. Advancing the ignition timing prolongs the time to compress the burning gases. The pre-ignition temperature also elevates gradually, since the pressure and temperature of the combustible mixture is low before ignition. Advancing your timing elevates firing end temperatures.

What is pre-ignition?
Pre-ignition is defined as the ignition of the air/fuel mixture before desired ignition timing.

What is detonation?
Detonation is a spark plugs worst enemy. It can break insulators and ground electrodes. Spark plug temperatures can reach in excess of 3000 °F.
Detonation, in simple terms, is a violent uncontrolled burn of the air/fuel mixture, which occurs when excessive heat and cylinder pressure causes the air/fuel mixture to spontaneously ignite.


Can I use platinum plugs with nitrous injection?
No, it is not suggested to use platinum plugs with nitrous oxide injection.
There have been instances where the platinum tip has lost its bond to either the center or ground electrode when they were used in a motor with nitrous.
Thus far the tech's say they have had no problems using Iridium plugs with nitrous.

Can I use Iridium plugs with nitrous injection or a blown alcohol motor?
A-. Yes, and Yes.
We double checked with the tech’s on this one, they say, while they have been watching for problems, thus far, there has been no reports of any problems in using iridium plugs with a nitrous system.
There should not be any problems using Iridium with a blown alcohol motor


I have slightly modified my motor, do I need a colder spark plug?
Possibly(more info below)

What is the torque setting for my plugs?
Plug torque settings

It is essential to tighten a spark plug to the specified turning angle or torque setting. This is for a number of reasons, over tightening can cause;
1) Damage to the threads in the cylinder head (especially aluminum heads).
2) Damage the threads of the spark plug.
3) Damage the internal seal of a spark plug allowing combustion chamber blow-by.
Under tightening of the spark plug can cause plug overheating and possibly pre-ignition. This is because one of the primary purposes of the spark plug is to remove heat from the combustion chamber, it does so by transferring that heat to the engine head. If the plug is not properly tighten it will not have sufficient contact with the head to transfer that heat. Proper tightening procedure is described below.

**Torque 14-22 ft-lb**(as per FSM)

Should I gap my Iridium Plugs?
The manufacturers say NO.
This is because most people do not know how to properly gap a spark plug, and the center electrodes on the ultra-fine iridium can easily snap if mishandled. There is no warranty for snapped center electrodes. The manufacturers say an iridium spark plug will run so much better than a traditional plug, even if it is not gapped for that motor, that they would prefer you just leave it rather than risk snapping the center electrode.
Personally, we at sparkplugs.com, gap our iridium plugs for our own vehicles (we’re rebels). If you insist on gapping your iridium plug, please refer to Proper Gapping for instruction.

How long will my iridium spark plugs last?

A traditional iridium plug such as a Denso IK20 or NGK ZFR6FIX-11 both have iridium center electrodes, however the ground electrodes are the traditional nickel construction. The ground electrode will wear out first. The manufacturers are saying 40,000 to 60,000miles on iridium plugs. But they have to temper their projections as driving conditions and motor modifications differ. Typically we have found you can expect 60,000 to 80,000 miles on an unaltered motor. (the wife’s mini-van has had the Denso's for 76,000 miles, I examined 2 of the plugs, they had some minor spooning on the ground electrode, I put them back in and will likely change them in another 5,000 miles)

Both Denso iridium racing plug and some NGK Iridium racing plugs have iridium center and a platinum ground electrodes. If installed to a regular engine they would likely last longer than most people keep their car (barring any motor problems that can cause premature plug death). But, these usually come in heat ranges too cold for an unaltered motor and are usually used in racing applications where all bets are off.

For the traditional automotive market, the longest lasting plugs are the NGK "IFR" series and the Denso "SK" series. These have Iridium center and platinum tipped ground electrodes, however these are extremely limited in application as they only manufactured these in a couple of heat range configurations.

Can old spark plugs be cleaned?
Yes, you can clean spark plugs, but in most cases its not worth it.
We do not recommend it for a number of reasons. In short, you will not get the same performance from a cleaned plug as a new plug. This is because electricity likes sharp edges to discharge from, a used plug will already have wear, and cleaning may contribute to that wear even more. (depending on the cleaning method used) If you want to try it, the below cleaning procedure was supplied to us by an old motor head. Good luck!
If the firing end is wet, make sure you clean the spark plug with a quick drying cleaner. (Examples: contact cleaner or brake cleaner).
Sand blast the spark plug using low air pressure and use a dry compound.
Completely blow all the sand from the spark plug.
Using a wire brush clean the threads and re-gap.
NOTE: Insufficient cleaning of the spark plug may lead to spark plug failure in a very short period of time. Clean the spark plug thoroughly to avoid problems later. Remember, if a spark plug is fouling it's usually a result of engine side factors or incorrect heat range selection.

Do I need to Gap my plugs?
Maybe, but likely not. Many plugs are pre-gapped for their most popular applications, however, the gap can be altered if the plug is dropped or mishandled in packing/shipping. Therefore even if the plugs are supposedly preset for your motor, it is always wise to check the gap on each plug prior to installing.It is not recommended you adjust the gap on multi-ground plugs.

What is proper spark plug gap for my motor?
.039-.043(as stated in the fsm)

What is the maximum I can open or close the gap?
Manufacturers don't recommend adjusting the spark plug gap < or > .008". The reason for this is the ground electrode and center electrode won't line up properly, hindering spark plug performance.

Proper gapping
In most cases the factory set gap should conform to your vehicle specifications. However if it is necessary to widen the gap, do so with a tool that only pulls back on the ground electrode without touching the center electrode or the porcelain. To close the gap on a plug, gently tap the plug, electrode first on a hard surface.

Heat range
The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber.

The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.

Do not make spark plug changes at the same time as another engine modification such as injection, carburetion or timing changes as in the event of poor results, it can lead to misleading and inaccurate conclusions (an exception would be when the alternate plugs came as part of a single precalibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. The worst thing that can happen from too cold a plug is a fouled spark plug, too hot a spark plug can cause severe engine damage

much of the info taken from http://www.sparkplugs.com and http://www.ngksparkplugs.com

The following information was added by sky jumper:

NGK plugs (according to their official product line):

V-Power Copper -- BKR5E-11 -- $1.89 ea
G-Power Platinum -- BKR5EGP -- $2.99 ea
OE Laser Platinum -- PFR5G-11 -- $9.99 ea
OE Laser Iridium -- IFR5E11 -- $9.99 ea
Iridium IX -- BKR5EIX-11 -- $6.99 ea

I believe the Iridium IX, like the G-Power, do not have the platinum tipped ground electrode or the laser welded center electrode, hence they are cheaper than the two OE laser products.

http://www.ngksparkplugs.com/part_fi...engineid=30512

http://www.ngksparkplugs.com/product...x.asp?mode=nml

Originally Posted by IlyaK

Amen! Quoted for truth man. When I first got my 90 Geo Storm...I didn't care about cars. When I got my 92 Subaru Legacy...I started changing my own oil. When I got my 97 GXE...I changed the oil, brakes, and other suspension...as well as the occasional light mod (stereo, etc.) When I got my 99...I installed a full exhaust BY MY SELF (including headers on a cali spec). You grow the more you do...now I can tackle just about any car job and not have to pay a single dime to the dealer.

Originally Posted by Neo Raven456

If you want to be cheap, NGK Coppers, they perform fine I used them for a bit. If you want to do it like a dealership, NGK PFR5G-11 , double platinum tipped.

I personally use NGK IFR5E-11 Iridium tipped, heard good things about iridium tipped plugs.

as far as changing your plugs, get a ratchet, 8mm socket, spark plug socket, an extension, phillips screw driver and an allen set. remove the valve cover, unplug/unscrew/remove the coilpacks, then remove the plugs and swap. As for the rears, same deal.