Spark plug heat ranges chart

Resistor type spark plugs reduce the amount of radio frequency interference (RFI) that can cause ignition misfires and static on the radio. [V] Shell Design - This refers to the thread size and reach of the spark plug. [15] Heat Range - The middle number indicates the heat range of the spark plug, the higher the number the hotter the heat range.

Spark plug heat ranges chart. The heat range of a Champion spark plug is indicated within the individual part number. The number in the middle of the letters used to designate the specific spark plug gives the heat range. For instance, if a Champion spark plug’s number is RCJ6Y, the heat range is 6. With Champion spark plugs, a higher number in the middle of the part ...

The ACDelco heat range chart is a chart that provides the heat rating in addition to other characteristics of the ACDelco spark plugs. The heat rating indicates the thermal charact...

Spark plugs come in different heat ranges. To make it easy for you to see the heat range of your spark plug, the number is printed into the plug’s part number. Here is how it works. The smaller ...Causes can include the engine overheating, incorrect spark plug heat range, a loose spark plug, incorrect ignition timing or too lean of an air/fuel mixture. The spark plug should be replaced. Worn electrodes. Worn and eroded electrodes are symptoms of a spark plug that is past its prime. The plug has been in the engine too long and needs to be ...Sep 15, 2022 · The optimum spark plug heat range is between 5000 C to 8000 C (or between 900 0 F to 1500 0 F) If the spark plug is operating at a temperature below the optimum range, then you will start noticing carbon deposits. If, on the other hand, the spark plug temperature is too high, there will be pre-detonation. The air-fuel mixture will start burning ... ACDelco Spark Plugs feature only high-quality parts to help ensure durability and consistent performance: Electrodes built on a foundation of iridium, platinum or copper. 100% copper cores. Spark plugs are protected with one-piece ceramic insulators. We offer a full line of ACDelco Spark Plug products. Whether you are choosing from our iridium ...Iridium. Iridium is said to be six times harder and eight times stronger than platinum with a 700° higher melting point. Iridium spark plugs have extremely fine electrodes while retaining excellent wear characteristics. Thanks to this strength, iridium spark plugs can last up to 25% longer than comparable platinum spark plugs.acdelco.com.au

A cold heat-range spark plug (left) can be identified by its rather shallow depth between the porcelain and the spark-plug body. A hotter plug (right) creates a much longer heat path to the plug shell that raises its operation temperature. Photo: Jeff Smith.Typically the heat range for NGK Spark Plugs varies from 2-11. This number indicates the thermal characteristics of a spark plug, or how ‘hot’ or ‘cold’ a spark plug is. The term hot/cold is commonly used to describe …Step 1: Get the tools and the new spark plug (as per the desired heat range of 7 or 6) Step 2: Allow time for the vehicle to cool down. Step 3: Disable the connectivity with the battery. Step 4: Depending on your vehicle’s design, remove the coil-on-plug connectors or spark plug wires.Here's a breakdown of the two main types: Cold Spark Plugs: These plugs feature a shorter porcelain insulator and ground strap, allowing heat to dissipate quickly. Cold spark plugs are ideal for high-performance applications or vehicles with increased cylinder pressure. Hot Spark Plugs: Conversely, hot spark plugs have a longer …Choosing the right spark plugs for your vehicle is essential for its optimal performance and fuel efficiency. With so many options available in the market, it can be overwhelming t...A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages. Normal rates of gap growth are as follows: Four-Stroke Engines: 0.01~0.02 mm/1,000 km (0.00063~0.000126 inches/1,000 miles)

Mar 29, 2010 · The heat ranges may be drastically different between two different plugs, and engine damage or poor performance may result. See your local installer or retailer for details. (Bold mine.) The prefix “41” stands for the manufacturer’s product line (e.g., 41 = spark plug) Numbers after the prefix indicate the type of spark plug and also the ... Onan Spark Plugs: Both the 4K & 6K use the same heat range spark plug. Plug gap for both is .020” Cummins Onan spark plugs are part# 167-0262-99 <$7. The X-‐7525B service manual Section 24C page28 calls for the use of an AC Delco R46S spark plug. Possible spark plugs that cross for AC DELCO R46S:Heat Range Chart Cross reference . Cold Hot. Brisk. 8. 10. 12. 14. 15. 17. NGK. 10. 9. 8. 7. 6. 5. Denso. 31. 27. 24. 22. 20. 16A wildfire near my house is a dangerous situation because wildfires are known to spread rapidly. Learn about a wildfire near my house. Advertisement In just seconds, a spark or eve...2399 Resistor. 2456 Non-resistor. 7806 Inductive suppressor. 8251 Xtreme Start. 8252 Xtreme Sport. 8290 Tapered seat. 8291 .060" Gap. 8293 Bantam plug with 3/4" hex. 8294 Power tip. 8295 Special lawnmower plug. 8297 Bantam spark plug. 8301 Special power tip. 8-69. Autolite® Spark Plug Heat Range Chart. Tableau des températures des bougies ...Ignition. ACCEL HP Spark Plugs are made with a Copper core which is a better conductor than Platinum and Iridium. They deliver a stronger spark especially in high performance applications where high combustion pressures are present. Copper is much better at dissipating heat than other materials which lessens the chance of a misfire.

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Advertisement The following animation shows a two-stroke engine in action. You can compare this animation to the animations in the car engine and diesel engine articles to see the ...The heat ranges may be drastically different between two different plugs, and engine damage or poor performance may result. See your local installer or retailer for details. (Bold mine.) The prefix “41” stands for the manufacturer’s product line (e.g., 41 = spark plug) Numbers after the prefix indicate the type of spark plug and also the ...268 posts · Joined 2022. #21 · Aug 13, 2022. Here, put "champion rule for spark plug heat range" in google. "According to Champion Spark Plugs, for normally aspirated, gasoline-fueled engines, a good rule of thumb is to go about one heat range colder for each full point in compression ratio increase from 9:1 through about 12.5:1, and two heat ...A good rule of thumb: use one heat range colder for every 75–100hp added. 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 numbering system used by spark plug manufacturers is not universal.Heat Range: 4 Hex Size (mm): 16mm ... Spark plug designs include continuous improvements, Resist oxidation and arc erosion, Multi-rib insulator protects against misfire, Nickel-plated shell for corrosion resistance (on all except Standard Copper Core), High strength Steel High Thread, Platinum-Iridium, and Fine Wire Double-Platinum feature 0.8 ... temperature of the tip of the spark plug. If the heat range is too cold, the deposits will not burn off the tip and the spark plug will foul. If the spark plug heat range is too hot, pre-ignition can occur. A switch in heat range of the spark plug will change the temperature of the spark plug tip by 70-120 degrees.

Take a look at the chart for the range of Champion offerings. Please note that the numbers don’t indicate degrees; they’re product codes to give an indication of the heat range. The higher the number, the hotter the plug, and the lower the number, the colder the plug.and material, plugs produced by various manufacturers do not have exactly the same heat range. Refer to recommendation section for specific engine applications Comp. Part# NGK STK # NGK # Comp. Part# NGK STK # NGK # Comp. Part# NGK STK # NGK # 44 3510 B6S 41-963 7740 PTR5C-13 45FFS 6222 BPR5HS 45 3210 B4 41-965 2467 PTR5A-13 …Here's a breakdown of the two main types: Cold Spark Plugs: These plugs feature a shorter porcelain insulator and ground strap, allowing heat to dissipate quickly. Cold spark plugs are ideal for high-performance applications or vehicles with increased cylinder pressure. Hot Spark Plugs: Conversely, hot spark plugs have a longer … A spark plug's heat range is the degree to which it disperses heat. Find out what the appropriate heat range is for your particular spark plug! Using the chart, and an example part number of BPR5ES-11, the specs of this spark plug have been highlighted to show that it has a thread size of 14.0mm, hex size of 20.8mm, a projected insulator type construction, resistor, heat rating of 5, 19.0mm thread reach, standard type firing end construction and a 1.1mm spark plug gap. RN7YC; now Champion 332. RN9YC; now 415. RN11YC4; now 322 (also given for N10Y) RN12YC; now 404. RN14YC; now 405. Andy referenced www.sparkplugs.com where I pulled the table below showing the Champion naming convention for their plugs. The higher the number, the hotter the plug. MSD Cross Reference with DENSO ® Stock Number to Plug Type. 3021 W16EPR-U 37334 11IR5Y 3036 W16P-U 37394 15IR5Y 3057 W20ESR-U 37344 11IR6 3076 W20SR-U 37404 15IR6[V] Shell Design - This refers to the thread size and reach of the spark plug. [15] Heat Range - The middle number indicates the heat range of the spark plug, the higher the number the hotter the heat range. [YC] Firing End Design - The letters after the heat rating indicates a special spark plug construction feature called the firing end ...A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages. Normal rates of gap growth are as follows: Four-Stroke Engines: 0.01~0.02 mm/1,000 km (0.00063~0.000126 inches/1,000 miles)Feb 2, 2010 · The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of NGK spark plugs is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type. May 7, 2023 · Maximizing Performance With The Spark Plug Chart. The spark plug chart is a valuable tool for maximising your engine’s performance. It provides information on plug temperature, heat range, and pre-ignition issues. By understanding these factors, you can choose the right spark plug for your engine ‘s needs.

Spark Plug Torque Recommendations | Champion Auto Parts Small Engine Spark Plug Troubleshooting Guide Decoding Champion Spark Plugs Tech Tips Choosing the Right Spark Plug Gap Tool Choosing the Right Spark Plug Heat Range. Installation Guides. How To Change Spark Plugs | Champion Auto Parts. Regular Maintenance. Diagnostic …

A spark plug's heat range indicates how much heat the plug is able to remove from the combustion chamber. That seems a little counterintuitive, as you may think that it would refer to the amount of heat generated by the plug on ignition, but no. Spark plugs run at a temperature of 500 to 850 degrees at the tip.The numbers on spark plugs indicate properties such as spanner width and design, heat rating, thread length, construction features and electrode distances. Different manufacturers ...This process involves making a pull (on a dyno or a pass), and shutting down the engine ASAP so the reading isn't tainted by idle time. Then the plugs are pulled and inspected. After a change is ...Onan Spark Plugs: Both the 4K & 6K use the same heat range spark plug. Plug gap for both is .020” Cummins Onan spark plugs are part# 167-0262-99 <$7. The X-‐7525B service manual Section 24C page28 calls for the use of an AC Delco R46S spark plug. Possible spark plugs that cross for AC DELCO R46S:However, because of more exposure to high temperature combustion gases and because ground electrode becomes longer, heat resistance and durability decrease. The higher the level of tuning, the greater the need is to use a less projecting type. As the level of tuning is increased, so does the need for higher heat range.Racing Heat Range and Tuning Guide. 12 page guide by Champion Sparking Plug Co. Ltd.'s Competition Department, 1973. Introduction. With modern sophisticated engines, new ceramics and superior alloys for spark plugs, the job of selecting a plug for a specific engine has become more critical.Take a look at the chart for the range of Champion offerings. Please note that the numbers don’t indicate degrees; they’re product codes to give an indication of the heat range. The higher the number, the hotter the plug, and the lower the number, the colder the plug.Advertisement You can understand a two-stroke engine by watching each part of the cycle. Start with the point where the spark plug fires. Fuel and air in the cylinder have been com...

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NGK’s performance and heat dissipation capacity cannot beat that of Champions. Conductivity. Champion Spark Plug is better and has higher conductivity than NGK. NGK spark plugs have better and higher conductivity. Size. Tread Diameter:0.551. Gap Size: 0.40 inch. Type. Copper plus spark plug.All the right spark plugs, recommended by Ford Motor Company. The Motorcraft ® name means quality, performance, reliability and confidence. All of these can be found in each Motorcraft ® spark plug. Motorcraft ® spark plugs are available for a broad range of applications, including domestic and import cars and trucks of all makes and sizes.However, because of more exposure to high temperature combustion gases and because ground electrode becomes longer, heat resistance and durability decrease. The higher the level of tuning, the greater the need is to use a less projecting type. As the level of tuning is increased, so does the need for higher heat range.The contrast with state institutions is glaring, even though many of them have a much better academic reputation. Like many government-run entities, public universities in India of...A spark plug's heat range indicates how much heat the plug is able to remove from the combustion chamber. That seems a little counterintuitive, as you may think that it would refer to the amount of heat generated by the plug on ignition, but no. Spark plugs run at a temperature of 500 to 850 degrees at the tip. Object moved to here. Advertisement You can understand a two-stroke engine by watching each part of the cycle. Start with the point where the spark plug fires. Fuel and air in the cylinder have been com...DENSO Spark Plug Heat Range. Published4 July 2019. Ask An Expert: Heat range is one of the most important and often misunderstood factors when choosing the correct spark plug for your engine. Let our DENSO expert explain how it all works. Heat Range. Temperature curves of spark plugs with different heat-range code numbers at full load in the same engine. j Spark plug with high heat-range code number (“hot plug”). Large insulator nose area absorbs more heat, low heat dissipation. —————— Heat-absorbing surface. - - - - - - Thermal conduction path. 2399 Resistor. 2456 Non-resistor. 7806 Inductive suppressor. 8251 Xtreme Start. 8252 Xtreme Sport. 8290 Tapered seat. 8291 .060" Gap. 8293 Bantam plug with 3/4" hex. 8294 Power tip. 8295 Special lawnmower plug. 8297 Bantam spark plug. 8301 Special power tip. 8-69. Autolite® Spark Plug Heat Range Chart. Tableau des températures des bougies ...Champion 868 Spark Plug RJ19LM RJ19LM. We have the Champion 868 Spark Plug RJ19LM you need with fast shipping and low prices. ... Heat Range: 19: REF. NO. 868: Thread : 14mm: Hex Size : 13/16" Customer Reviews for the 868 Spark Plug RJ19LM Review Rating: Sort By: by Jeff N. Reviewed on 2/5/2024 10:07:04 AM. Review: good …Spark Plugs. You never forget your first Champion ®. Our spark plugs have been improving engine performance since 1907. Choose your next Champion from the range of plugs that live up to the legacy of this iconic brand. ….

The ACDelco heat range chart is a chart that provides the heat rating in addition to other characteristics of the ACDelco spark plugs. The heat rating indicates the thermal characteristic of the spark plug, or how hot or how cold the spark plug is. The chart details the plug identification table. It consists of possible spark plug prefix values ...Watch this video to find out about the importance of using a kitchen range hood vented to the outside to remove heat, moisture, and pollutants from cooking. Expert Advice On Improv...Spark Plug Metallurgy Comparison Chart. Iridium Double Platinum Platinum Copper. Mileage / Service Life. ... Noble metals resist corrosion better, preventing fouling plugs. Spark plugs that are less likely to foul provide quicker acceleration. Slower Acceleration Quicker Acceleration.[V] Shell Design - This refers to the thread size and reach of the spark plug. [15] Heat Range - The middle number indicates the heat range of the spark plug, the higher the number the hotter the heat range. [YC] Firing End Design - The letters after the heat rating indicates a special spark plug construction feature called the firing end ...I understand that the heat range of plugs is determined by the length of the insulator and electrode length beyond the shell of the plug body but here's the deal. The R44T's and the R45T"S are identical in looks whereas the R44TS's extend quit a bit beyond the plug shell.Nov 5, 2022 · The spark plug heat range scale typically ranges from 2 to 12, with 2 being the coldest and 12 being the hottest. It’s important to note that the heat range scale may vary slightly depending on the manufacturer. When selecting a spark plug, it’s crucial to choose the appropriate heat range for your engine. Well, below you will find a “heat range cross reference chart” that shows comparisons between 5 major brands of spark plugs. NGK. DENSO. Pulstar. Champion. Bosch. Heat. 2. 9.The heat range of a Champion spark plug is indicated within the individual part number. The number in the middle of the letters used to designate the specific spark plug gives the heat range. For instance, if a Champion spark plug’s number is RCJ6Y, the heat range is 6. With Champion spark plugs, a higher number in the middle of the part ...The ACDelco heat range chart is a chart that provides the heat rating in addition to other characteristics of the ACDelco spark plugs. The heat rating indicates the thermal characteristic of the spark plug, or how hot or how cold the spark plug is. The chart details the plug identification table. It consists of possible spark plug prefix values ...What is the difference between a 6 heat range spark plug and a 9 heat range plug? And which one should you choose if you have modified your engine? SUBSCRIBE... Spark plug heat ranges chart, Yamaha's YZF-R6 has been a favorite among track-day riders and racers. Praised for its agility and lightweight frame, the R6 has earned a reputation for performance. While the bike..., Para obtener la aplicación correcta de su vehículo, por favor referirse a la sección correspondiente dentro de esta guía. 410. Competitor # NGK Stock # NGK Part # Competitor # NGK Stock # NGK Part # Competitor # NGK Stock # NGK Part # ACDelco. R43T6 7240 YR55 R43TS 2771 UR5 R43TS6 2248 UR55 R43TSK 2771 UR5 R43TSX …, The heat range of a Champion spark plug is indicated within the individual part number. The number in the middle of the letters used to designate the specific spark plug gives the heat range. For instance, if a Champion spark plug’s number is RCJ6Y, the heat range is 6. With Champion spark plugs, a higher number in the middle of the part ..., Spark plugs with a high degree of heat dispersal are called high heat range (cold type) and those with a low degree of heat dispersal are called low heat range (hot type). This …, Firstly, consider the heat range. A colder spark plug, such as the HD-6R12 plug, is ideal for high-performance engines or those running at higher RPMs. ... A spark plug chart helps in choosing the right spark plug for your application, whether it’s Iridium spark plugs or standard plugs. It ensures that during service, when using a torque ..., Watch this video to find out about the importance of using a kitchen range hood vented to the outside to remove heat, moisture, and pollutants from cooking. Expert Advice On Improv..., Nitrous (one step colder) Heat Range: 10. Gap: Consult ignition mfg. Plug: NGK 5672A-10 (stock number 7942); Autolite AR50; Denso IQ31 (stock number 5323) Nitrous (two steps colder) Heat Range: 11. Gap: Consult ignition mfg. Plug: Denso IQ34 (stock number 5324) LT1 w/ Trick Flow & Edelbrock Heads., Advertisement You have your fire pit and a nice collection of wood. The only thing between you and a nice evening roasting s'mores is a spark. There are many methods for starting a..., Selecting the right spark plug means considering several factors, including the heat range. Learn how to select the proper heat range, and cross reference codes by manufacturer., Heat Range Chart Tableau des températures de bougies Tabla de Rango Térmico Reach/Portée/Alcance Projection/Prolongé/Proyección Hex Size/Hexagonal/Hexágono , Take a look at the chart for the range of Champion offerings. Please note that …, If it the heat range is too hot, your engine could experience detonation, pre-ignition, or power loss. Most spark plug manufacturers recommend that the tip temperature remain between 500-850 degrees Celsius. Diagram courtesy of NGK Spark Plugs. Heat ranges are designated by each spark plug manufacturer with a number., Recently, I’ve talked quite a bit about connecting to our creative selves. (Yes, everyone is creative!) One Recently, I’ve talked quite a bit about connecting to our creative selve..., May 7, 2023 · Maximizing Performance With The Spark Plug Chart. The spark plug chart is a valuable tool for maximising your engine’s performance. It provides information on plug temperature, heat range, and pre-ignition issues. By understanding these factors, you can choose the right spark plug for your engine ‘s needs. , A wildfire near my house is a dangerous situation because wildfires are known to spread rapidly. Learn about a wildfire near my house. Advertisement In just seconds, a spark or eve..., Spark Plugs. You never forget your first Champion ®. Our spark plugs have been improving engine performance since 1907. Choose your next Champion from the range of plugs that live up to the legacy of this iconic brand., AGSF32C - Short name: SP447. Recommended for 1993 Cobra, GT40 Heads. A = Thread Diameter = 14 mm. G = Reach = .708" Conical Seat. S = Plug Characteristic = Suppressor (Carbon) F = Plug Characteristic = Conical Seat. 3 = Heat Range = Cold (Stock) 2 = Tip Configuration = Extended (Power) Tip. C = Plug Characteristic = Copper Core Electrode., Check for faulty or sticking choke, overly rich fuel mixture, ignition problems, leaking fuel injectors, or spark plug heat range is too cold.Appearance - Firing tip is damp with gasoline, usually the odor of fuel is present on the spark plug. The insulator is often tinted the color of charcoal.These usually look WET and smell of gasoline., The heat range of a Champion spark plug is indicated within the individual part number. The number in the middle of the letters used to designate the specific spark plug gives the heat range. For instance, if a Champion spark plug’s number is RCJ6Y, the heat range is 6. With Champion spark plugs, a higher number in the middle of the part ..., Spark Plug Thread Size: 14mm . Spark Plug Reach (in.): 0.750 in. Spark Plug Reach (mm): 19.05mm . Shorty Spark Plug: No . Resistor: No ... These replacement spark plugs are available in colder heat ranges than most plug manufacturers to support modified engines. They feature a cut background electrode, which improves ignitibility and faster ..., Principle Applications & Specifications. Passenger Cars & Light Trucks 2011 - 1996. Passenger Cars & Light Trucks 1995 - 1960. Recreational Vehicles - Motorcycles. Commercial Equipment - Lift Trucks. Small Engine - Power Equipment Engines. Installation Bulletin for High Thread Series Spark Plugs., Glow plugs, heat ranges, and the correct plug for the right application. Different brand GLO plug numbers, are MEANINGLESS between manufactures...And while a A3 OS and #8 OS are both hot, they are not the same plug. OS A3 plugs cost $3.50each....OS#8 are $5.00 each. OS A5 and OS R5 cost $6.00each., Spark plug charts are sorted by thread size, thread reach, hex size. Hotter plugs are listed above the colder plugs. Plug images are located on the opposite page. NGK Racing NGK Standard Part No. Stock No. Image Part No. Stock No. Image Racing Spark Plugs 14mm Spark Plugs (cont.) 3/4” Reach R5184-95 7485 291 IC 13/16” Hex R5184-10 7457 291 IC, ACDelco Spark Plugs feature only high-quality parts to help ensure durability and consistent performance: Electrodes built on a foundation of iridium, platinum or copper. 100% copper cores. Spark plugs are protected with one-piece ceramic insulators. We offer a full line of ACDelco Spark Plug products. Whether you are choosing from our iridium ..., Spark Plugs. You never forget your first Champion ®. Our spark plugs have been improving engine performance since 1907. Choose your next Champion from the range of plugs that live up to the legacy of this iconic brand., ACDelco Spark Plugs feature only high-quality parts to help ensure durability and consistent performance: Electrodes built on a foundation of iridium, platinum or copper. 100% copper cores. Spark plugs are protected with one-piece ceramic insulators. We offer a full line of ACDelco Spark Plug products. Whether you are choosing from our iridium ..., Dec 24, 2020 · Low power engines – low heat range or hot spark plug. High power engines – high heat range or cold spark plug. Heat Range Reference Chart. As we mention above, the heat range for NGK spark plugs varies from 2-11. Let’s take a look on the heat range chart where there is full information about the number. , Heat Range: 10 Gap: Consult ignition mfg. Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321) **NOTE: Use chart for static compression and adjust heat range for nitrous use accordingly. LS1 Stock and AFR Thread – 14mm Reach - .708” Socket – 5/8 hex Seat - …, Replace with a new set of Autolite spark plugs. 6. GLAZING Recommendation: Spark plug is operating too hot at high speeds. Replace with a colder heat range of Autolite spark plug. 7. CARBON FOULED Recommendation: Spark plug heat range is too cold and/ or caused by extensive low-speed, short distance driving. Replace with the correct heat range ... , DENSO Spark Plug Heat Range. Published4 July 2019. Ask An Expert: Heat range is one of the most important and often misunderstood factors when choosing the correct spark plug for your engine. Let our DENSO expert explain how it all works., and material, plugs produced by various manufacturers do not have exactly the same heat range. Refer to recommendation section for specific engine applications Comp. Part# NGK STK # NGK # Comp. Part# NGK STK # NGK # Comp. Part# NGK STK # NGK # 44 3510 B6S 41-963 7740 PTR5C-13 45FFS 6222 BPR5HS 45 3210 B4 41-965 2467 PTR5A-13 …, Nov 5, 2016 ... A good rule of thumb: use one heat range colder for every 75–100hp added. In identical spark plug types, the difference from one full heat range ..., recommended heat range Overheating • Appearance: Discoloration of the ceramic insulator, near to the shell • Cause: Particles of oil/gas (in the spark plug well), becoming attracted to the ceramic by the magnetic field created by the high voltage current flowing through the spark plug • Effect: Not detrimental to spark plug operation