Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel plating, and large ground electrode for better heat transfer. Heat range needed with Standard tip or Power tip, Hottest. 14 mm plug .75" reach 5/8" hex Gasket seat Non-resistor Set of 8 Vendor Number: AR3934 Note: Please use the Vendor Number to reference the …This means the spark plug will heat up easily and reach its optimal operating temperature. High performance engines on the other hand produce a large amount of heat, hence a high heat range (or cold) spark plug such as a 10 heat range needs to be used to resist the heat developed by the engine. Several factors influence the heat range of a ...TIP TEMPERATURE IDLE VEHICLE SPEED FULL THROTTLE Each engine has different temperature characteristics; typical plug temperature ranges are illustrated above. The shorter the path, the faster the heat is dissipated and the cooler the plug. Heavy Loads / High Speeds • SHORT Insulator Tip • Fast Heat Transfer • LOWER Heat Range • COLD PLUG autolite heat range chart. spark plug heat range guide. champion spark plug heat range chart. ngk spark plug heat range chart. ac delco spark plug heat range chart. spark plug heat range comparison chart. That should keep ya busy reading for a while:tongue5: Apr 29, 2012. #3.General F150 Discussion - The difference between Motorcraft and Autolite spark plugs - So, I have a small digital microscope available here in the shop, and I wanted to say thanks to the forum for all the help, so I thought I would take some closeups of the differences between the Autolite plugs and the Motorcrafts...These plugs should have the proper fit & heat range and You can use any brand but do not go over the equivalent of a Delco 45 heat range. found this chart but the heat ranges are all over the place AC DELCO 45 - Alternative spark plugs Accel 124 Autolite 295 Autolite 316 Beru 14-10E Beru 14-8E Bosch 0241225548 Bosch W10EC Bosch W8E Bosch W9EC ...Cobb Carpet Supply Spark Plug Heat Range Chart - Used to compare Spark Plug Brands Kohler 34-40 HP TM Engine Champion RC10YC . Home; Log In . Main Store (please note new address) 444 W. Mockingbird Ln., Dallas, TX 75247-6614 Phone (800) 634-2622 Hours: 8:00a to 5:00p M-F: Northeast BranchThe ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine.Autolite 275 - Alternative spark plugs. Autolite 275. - Alternative spark plugs. There are 207 replacement spark plugs for Autolite 275 . The cross references are for general reference only, please check for correct specifications and measurements for your application.Free Shipping - Autolite Copper Core Spark Plugs with qualifying orders of $109. Shop Spark Plugs at Summit Racing. $20 Off $250 / $50 Off $600 / $125 Off $1,320 - Use Promo Code: TREAT. ... Manufacturer Heat …Find Autolite Racing Spark Plugs and get Free Shipping on Orders Over $109 at Summit Racing! Autolite racing spark plugs are the preferred choice for many professionals. They contain an Yttrium-enhanced alloy, which enables up to 8 percent reduction in side wire temperatures for improved durability and less pre-ignition. These replacement spark plugs are available in colder heat ranges than ...spark plug. You to autolite heat range chart purchase your application, and the autolites left from the brands ads and those existing will burn and! Atv spark cross references plug brands ads and autolite heat when you are general reference charts contain a spark plug heat done! Expect to ngk are the autolites left from ac delco spark plug crossThere are 145 replacement spark plugs for Autolite 85 . The cross references are for general reference only, please check for correct specifications and measurements for your application. Autolite 85 replacement spark plugs. Accel 0437.The ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine.Iridium Ultra ® is our most technologically advanced plug that is engineered to meet or exceed OE standards in late model engines. With a laser-welded finewire center electrode, Autolite Iridium Ultra ® delivers optimal fuel efficiency and acceleration, greater ignitability, and improved durability for more than 100,000 miles; making it the best spark plug replacement choice for modern engines.Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel plating, and large ground electrode for better heat transfer. Heat range needed with Standard tip or Power tip Colder. 14 mm plug .75" reach 5/8" hex Gasket seat Non-resistor Vendor Number: AR3911 Note: Please use the Vendor Number to reference the PDF chart links listed. Item Details Colder Power Tip Vendor ...The relationship between the spark plug temperature and vehicle speed and heat range is expressed with a graph like that in the figure. There are restrictions on the temperatures at which spark plugs can be used: the lower limit is the self-cleaning temperature and the upper limit is the pre-ignition temperature.A spark plug only functions completely when its center electrode temperature is ...DPR5EA-9 is the part number and 2887 is the stock number. The exception to this is racing plugs. An example of an NGK racing plug is R5671A-11. Here, R5671A represents the plug type and -11 represents the heat range. The stock number is 6596. NGK lists a design symbols chart in the front of every spark plug catalog. We break down how to decode ...1. Stay cool enough to avoid pre-ignition and/ or electrode destruction. 2. Run hot enough to burn off combustion deposits that would otherwise collect at the firing tip. 3. Adapt to …Autolite spark plug heat range is generally indicated by the last digit of the part number. Higher number indicate hot plug (for example 5 or 4) and low number indicate cold heat …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.auto crossover chart beru to e3 berue3beru e3beru e3 autolite to e3 autolite e3 autolite e3 autolite e3 ap5125 e3.72 ap5143 e3.53 ap5144 e3.60 ap5145 e3.60 ap5224 e3.48 ap5243 e3.53 ap5245 e3.54 ap5263 e3.66 ap5503 e3.56 app23 e3.40 app24 e3.40 app25 e3.42 app26 e3.42 app45 e3.72 app63 e3.46 app64 e3.46 app65 e3.46 app66 e3.46 app103 e3.53 ... Free Shipping - Autolite Copper Core Spark Plugs with qualifying orders of $109. Shop Spark Plugs at Summit Racing. $20 Off $250 / $50 Off $600 / $125 Off $1,320 - Use Promo Code: TREAT. ... Manufacturer Heat Range: 5 . Shorty Spark Plug: No . Resistor: Yes . Electrode Tip Material: Copper . Electrode Core Material: Copper ...Non-Projected | Plug Reach | Comparison Chart | Spark plug heat range refers to the insulator (white ceramic) nose length where the ceramic meets the metal core to the firing tip. The insulator is typically the hottest part of the spark plug and is the main cause of pre-ignition and fouling. ... Autolite 25 - Excl. 1986: OEM Replacements: Stock ...The ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine.The 1970 454 with 345 hp takes a r44t.With 390 hp takes a r43t. Al. I learned there are 2 different size (length) plugs for this application. It is tricky. My heads are from a 1969-1970 passenger car per the casting number. the block is a 1979 chevy truck.Understanding Multiple Ground Electrode Spark Plugs. Spark Plug Type. Understanding Spark Plug Sizes. Spark Plug Tip Diagnosis. Understanding Spark Plug Heat Ranges. Understanding Autolite Spark Plug Numbering System. Torque Specifications. Heat Range Facts. Half Thread/Full Thread Explanation.AUTOMOTIVE SPARK PLUGS. As a world leader in spark plug manufacturing, Champion ® knows what it takes to keep your engine running at its best. When it's time to replace your plugs, Champion ® your engine with spark plugs that help improve performance and reduce wear and tear.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. …The 1970 454 with 345 hp takes a r44t.With 390 hp takes a r43t. Al. I learned there are 2 different size (length) plugs for this application. It is tricky. My heads are from a 1969-1970 passenger car per the casting number. the block is a 1979 chevy truck.MouseFink · #4 · Mar 29, 2013. AC Delco spark plugs, "R" means resistor type, "46" means: "4" is the 14mm threads and "6" is the heat range and "S" means projected tip. A "6" is the hottest AC Delco spark plug available. Besides, the heat range of the spark plug would not make any difference in exhaust sounds unless the previous …These plugs fire quicker and cleaner with less voltage, creating easier starts, quicker acceleration and improved fuel economy versus standard plugs. Platinum is one of the most durable metals used in spark plug tips today. Autolite (R) Platinum Spark Plugs feature: Patented design. Center wire platinum firing tip. Reduced gap erosion.If I have to go to another brand of plugs, brands and heat range suggestions are appreciated; I'm running 45's now and they are too hot (see link to photo above) B. BIGREDRASA 1K+ VIP. Aug 27, 2009 #6 ... System.pdf A chart showing Autolite plug heat range chart; ...EIGHT8 Autolite AR135 Racing Spark Plug SET fits Champion V63C NGK R5673-7 . USD 35.92 . Autolite Platinum Spark Plugs - MPN AP65 - Set of 6 Spark Plugs . USD 34.80 . Spark Plug-Copper Non-Resistor Autolite 3095 . USD 8.31 ...We make several hotter heat ranges in that style of plug, AR3923 and AR3924. The AR3935 is a very hot plug. That being said, a hotter plug will not clear up rich running at idle. If you used a hot enough plug to do that, you could say goodbye to the 540 on your first pass due to pre-ignition.Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel plating, and large ground electrode for better heat transfer. Heat range needed with Standard tip or Power tip: Hotter. 14 mm plug .75" reach 5/8" hex Gasket seat Non-resistor Vendor Number: AR3933 Note: Please use the Vendor Number to reference the PDF …Sorry you are misreading the chart,If the 2 numbers are in the same box on the chart they operate at the same heat range. The 45 and 5125 are the same heat range The 5125 is a plug of Long Shell design with an extended gap. Design gap is for .044 if you are gapping down to .035 you will not be able to keep the side electrodes square to the center.Spark Plug APP3923-Double Platinum Autolite APP3923 Box of 2 FREE SHIPPING . USD 8.89 . Spark Plug Autolite 3923 Fits Toyota Camry 2011-1990, Toyota Sienna 2006-1998 . USD 16.39 . Autolite Platinum AP3923 Spark Plugs pack of 4 . USD 9.95 ...Torque Specifications. Heat Range Facts. Half Thread/Full Thread Explanation. Autolite Copper Core Spark Plug Attributes. Understanding VIN Codes. Autolite Double Platinum Spark Plug Attributes. Original Equipment Platinum Spark Plug Applications. Spark Plug Cross Reference. Racing/High Performance Spark Plug: Heat Range Facts.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 - TaperAutolite 275 - Alternative spark plugs. Autolite 275. - Alternative spark plugs. There are 207 replacement spark plugs for Autolite 275 . The cross references are for general reference only, please check for correct specifications and measurements for your application.Competitor # NGK Stock # NGK Part # Competitor # NGK Stock # NGK Part # Competitor # NGK Stock # NGK Part # ACDelco 41-948 7300 TR4IX 41-948 7740 PTR5C-13Feb 2, 2020 · Thanks, Joe. Much appreciated. Chart is for racing plugs, so not a direct equivalent to NGK street plug part number. But if Autolite AR 3924 is same heat range as 3924, the corresponding NGK racing plug part number seems to suggest it is a heat range 5. MouseFink · #4 · Mar 29, 2013. AC Delco spark plugs, "R" means resistor type, "46" means: "4" is the 14mm threads and "6" is the heat range and "S" means projected tip. A "6" is the hottest AC Delco spark plug available. Besides, the heat range of the spark plug would not make any difference in exhaust sounds unless the previous …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 - TaperSearch this spark plug cross reference with more than 90000 models. Champion D21 - Alternative spark plugs. ... Autolite Spark Plug Pack of 4 Part No: A-386 . USD 19.99 . Autolite 388 Copper Resistor Automotive Replacement Spark Plugs (4 Pack) USD 6.17 . Denso (5000) L14-U Traditional Spark Plug, Pack of 1 ...I found NGK or Autolite to work the best on my 906 or 915 heads. ... 'Motorhome' heads. Champion OBL9Y or equivalent--you can alter the heat range of course ... Spark plug choice. old guys rule; Jan 13, 2023; Electrical & Ignition; 2 3. Replies 46 Views 4K. Feb 18, 2023. Cheapsunglasses. Share:Autolite SPARK PLUG. Part Number: 417-86. Product Q&A View Now. Click image to zoom. $3.09 Lowest Price Guarantee ... MSD Ignition 3738 - Iridium Spark Plug Heat Range: 4 $8.95. Add To Cart. $8.95. MSD Ignition . MSD Ignition 37384 - Iridium Spark Plug Heat Range: 4 $33.90. Add To Cart. $33.90.Detailed Description. Spark Plug; Racing; Non-Resistor; Yttrium-Enhanced Alloy enables up to 8 percent reduction in sidewire temperature for colder heat ranges designed to enable performance modifications and handle intense conditions. Cut back ground electrode for better ignitability of the flame kernel; Anti-corrosive nickel plating to ...Visit the Autolite Store. 3.8 2 ratings. · Genuine Autolite Part # 308. · Copper-glass seal bonded insulator, terminal post, and center electrode provide a tight seal that is 100 percent leak-proof. · Multi-rib insulator reduces danger of "flash-over" to prevent misfires. · Full copper core electrode improves heat transfer and optimizes ...No longer necessary as modern spark plug coatings work as a releasing agent and should be installed dry. Anti-seize can alter the tightening torque up to 20%, increasing risk of breakage. Anti-seize can create heat transfer and electrical conductivity concerns. Only use anti-seize where it is OE recommended.Since 1936, Autolite has been a trusted leader and innovator in spark plug technology. You can count on Autolite copper plugs for performance and value, backed by decades of experience and passion. Features & Benefits: Guaranteed to deliver quick starts, good fuel economy and smooth acceleration.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 ...Most spark plug manufacturers recommend that the tip temperature remain between 500° C and 850° C. Heat ranges are designated by each spark plug manufacturer with a number. In broad terms, spark plugs are often referred to as "hot plugs" or "cold plugs.". A cold plug has a shorter insulator nose length—the distance from tip to spark ...Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel plating, and large ground electrode for better heat transfer. Heat range Medium. Power Tip (Projected Tip) 14 mm plug 3/4" reach 13/16" hex Gasket seat Non-resistor Vendor Number: AR51 Note: Please use the Vendor Number to reference the PDF chart links listed. Item Details Medium Power Tip Vendor Part Number ...When choosing a spark plug for your engine, the approved options can be found in the aircraft and engine maintenance manuals. The plug part numbers can be easily decoded to explain the application in your engine. For example: Part Number: URHB32E. Translates to: U - Manufacturer (Tempest) R - Resistor Plug. H - Barrel Size (E = 5/8", H ...Dec 29, 2014 · Example a R5671A-7 (a good street/strip plug) is a cold plug where a R5671A-10 is a very cold plug used for large 400hp and up nitrous and other power adder applications) Autolite Heat Ranges - The larger the last digit in the part number, the hotter the plug is. Example a AR3935 (good street/strip plug) is hotter than a AR3932 plug which is ... Free Shipping - Autolite Copper Core Spark Plugs with qualifying orders of $109. Shop Spark Plugs at Summit Racing. $20 Off $250 / $50 Off $600 / $125 Off $1,320 - Use Promo Code: TREAT. ... Manufacturer Heat Range: 4 . Shorty Spark Plug: No . Resistor: Yes . Electrode Tip Material: Copper . Electrode Core Material: Copper ...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 ...Sparkplug Cross Reference Chart. Jump to Latest Follow ... There are 2 colder heat range plugs available: IXU24 IXU27 DENSO SPARK PLUGS - Basic Knowledge. ... Autolite-4164: 4133: 4265: 4164: 996-4123: 996: 4265: 2585-Autolite Platinum-AP4164DP2-AP4265DP2: AP4164DP2----AP4265DP2--Bosch / Platinum-YR6LDE: X4CS:The ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine.Copper core center electrode for higher thermal conductivity. Specially engineered high nickel alloy center and ground electrode for extended life. High alumina ceramic for high dielectric strength. Leak proof, heat fused internal seal for durability. Multi-rib insulator prevents flash-over. This spark plug is pre-gapped, but may require minor ...Free Shipping - Autolite Racing Spark Plugs with qualifying orders of $109. Shop Spark Plugs at Summit Racing. $20 Off $250 / $50 Off $600 / $125 Off $1,320 - Use Promo Code: ... These replacement spark plugs are available in colder heat ranges than most plug manufacturers to support modified engines. They feature a cut background electrode, ...Yttrium-Enhanced Alloy enables up to 8% reduction in sidewire temperature for colder heat ranges designed to enable performance modifications and handle intense conditions. Cut back ground electrode for better ignitability of the flame kernel. Autolite (R) Racing Hi-Performance are actual racing spark plugs used by many professional car drivers.NGK Spark Plugs R5671A-7 Ngk Plug 4091 Made by NGK Spark Plugs. USD 55.99. NGK Spark Plug Racing Box of 4 R5671A-7. USD 36.34. NGK (4091) R5671A-7 Spark Plug - Pack of 4. USD 22.57. NGK R5671A-7 Racing Spark Plug, One Size. USD 6.72. Autolite AR3935-4PK High Performance Racing Non-Resistor Spark Plug, 4 Pack.BF-32 Autolites are hard to find now, at least at $2 anymore. They'll tell you Autolite 45 is the same. Nope, it's hotter. One strategy that makes sense is to start with the coldest plug under consideration. Then work your way back up heat range wise.Detailed Description. Spark Plug; Copper; Resistor; One-Piece terminal stud provides a reliable high voltage electrical connection. High alumina multi-rib insulator helps prevent flash-over which can lead to misfires. Heat-fused glass composite resistor center seal provides high performance EMI noise suppression and a 100 percent leak-proof seal.Detailed Description. Spark Plug; Double Platinum; The platinum-to-platinum design of AutoliteDouble Platinum spark plugs greatly decreases gap erosion and reduces misfires. These are superior-performing spark plugs for distributorless ignition system (DIS) engines. Get up to 3X longer service life compared to standard copper plugs.The most critical factor for a spark plug that needs to be considered when an engine is modified is HEAT RANGE. Spark plugs are designed to operate in a temperature range of 450 – 870°C, when an engine is modified (generally to produce more power which produces more heat) in turn the engine and subsequent spark plug temperatures increase.Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel plating, and large ground electrode for better heat transfer. Heat range Colder. Standard tip 14 mm plug .460" reach 5/8" hex Tapered seat Non-resistor Vendor Number: AR13 Note: Please use the Vendor Number to reference the PDF chart links listed. Heat Range Chart (PDF) Racing Plug Tech Note (PDF ...spark plug. You to autolite heat range chart purchase your application, and the autolites left from the brands ads and those existing will burn and! Atv spark cross references plug brands ads and autolite heat when you are general reference charts contain a spark plug heat done! Expect to ngk are the autolites left from ac delco spark plug crossThe ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine.Spark Plug, Copper Core, Resistor, 14mm x 1.25, Gasket Seat, 0.750 in, Reach, Each ... Manufacturer Heat Range: 3 . Shorty Spark Plug: No . Resistor: Yes ... 13/16 in. Ground Strap Quantity: One . Quantity: Sold individually. Autolite Copper Core Spark Plugs. Autolite copper core spark plugs feature a cold-formed steel shell with precision ...Identifying Spark Plugs - The Green Spark Plug Company ... Half heat range-LM: Compact design. Insulator top: 14.5mm high-N: Strong ground electrode design: No Letter: 'V'-Grooved centre electrode (14mm thread dia. 19mm reach plugs only, eg: BKR6E: Others: A,B,D etc, - special design:The spark plug is heated during combustion and must dissipate that heat to the cylinder head at a certain rate to avoid overheating the ceramic firing end. The spark plug heat range only indicates the rate that the spark plug dissipates its firing end heat to the engine. A hotter heat range spark plug has an insulator design with a longer heat ... Spark Plug, Racing, Gasket Seat, 14mm Thread, .750 in. Reach, Non-Resistor, Each See More Specifications | Check the Fit. NGK Racing Spark Plugs R5671A-7 ... NGK Spark Plug Heat Range. NGK Spark Plug Terminal Types: Solid, Loose, Stud. NGK Spark Plug Over-Torque. NGK Spark Plug Under-Torque. NGK Spark Plug Proper Torque.Spark plug is operating too hot at high speeds. Replace with a colder heat range of Autolite spark plug. Appearance - Ceramic insulator tip appears to have a melted, glazed coating. You sometimes see a very bright white electrode with black dots on it also as a heat range issue in some cases cracked electrodes. See the Hall of Shame for oneMy tractors are work tractors. I have also had good luck with the Autolite 3116 and 386. My Dad swears by the Autolite plugs and will not use the Champions. ... While I'm not excited about the ethanol in our fuel, I'm not sure it has much impact on spark plug heat range. Top. HiltzMachineWorks 10+ Years Posts: 36 Joined: Wed Mar 14, 2012 12:17 ...Spark plugs with a hotter heat range will burn off carbon deposits more easily than a colder plug. "As an example, an Autolite copper 105 versus an XP Iridium 105 will have identical ceramic temperatures and the carbon burn off will be the same," says Reeves. A spark plug's reach is defined as the length of the threads.Automotive Spark Plugs. Every car is different, and so is every driver. Whether you just need a reliable set of copper replacement plugs or want to upgrade to peak performance, we've got you covered. The AC Delco Spark Plug Decoder Table Prefix and suffix letters are used to , Reference.com - What's Your Question?, auto crossover chart beru to e3 berue3beru e3beru e3 autolite to e3 au, spark plug no. principal application thread diameter reach hex se, Spark Plug APP3923-Double Platinum Autolite APP3923 Box of 2 FREE SHIPPING . USD 8.8, Dempster. Registered. Aug 27, 2009. #3. C7 was discontinued & replaced by Champion 541 / RD16 w, Autolite Racing spark plugs feature a cut back ground electrode, anti-corrosive nickel, Spark Plugs help remove heat from the combustion chamber., Sticking to the belief of "Creating products of h, more heat, low heat dissipation. k Spark plug with medium, The heat range will dictate how fast the plug tip will dissip, Autolite is one of the best selling spark plugs in Ameri, The heat range will dictate how fast the plug tip wil, Free Shipping - Autolite Copper Core Spark Plugs with q, Free Shipping - Autolite Racing Spark Plugs with qualifying order, China / East Asia. China. Taiwan. Korea. Japan. DENSO spark plugs use , Autolite Copper spark plugs deliver quick starts, , I found NGK or Autolite to work the best on my 906 or 915 heads..