buick special Posted July 31, 2017 Share Posted July 31, 2017 Hi Guys I was looking for a new set of spark plugs for my 1940 Buick special I called the parts guy and he said he did not have AC46 spark plugs I found a cross reference list below and he had some of them or alternatives his computer pulled up He said some look like small lawn mower plugs some do not some plugs he suggested were autolite 405 ngk 3110 champion 318 what is the correct plug?? here is the cross reference list from the web AC DELCO 46 - Alternative spark plug Replacement spark plugs for AC DELCO 46: Brand Model Accel 124 Autolite 295 Autolite 297 Autolite 306 Autolite 458 Bosch 0241225548 Bosch W9EC Bosch W9EC0 Bosch WR9EC Bosch stk 7515 Champion J11 Champion J11C Champion J19LM Champion RJ12C Champion stk 511 Champion stk 592 Champion stk 861 Denso 6004 Denso W9-U Denso W9U Denso stk 6004 Eyquem FS20 General Motors 1559494 Iskra FS20 Lodge BAN Motorcraft A11 Motorcraft A11LM Motorcraft AS8 Motorcraft stk 117 Motorcraft stk 77 NGK 3110 NGK 3210 NGK B-4 NGK B2 NGK B2-10 NGK B4 NGK stk 3110 NGK stk 3210 Prestolite 14-09-01 Splitfire SF045F Torch G4C Link to comment Share on other sites More sharing options...
MCHinson Posted July 31, 2017 Share Posted July 31, 2017 http://bobsautomobilia.com/electrical/spark-plug-1938-1942-1950-53-.-ac-r45/ Link to comment Share on other sites More sharing options...
buick special Posted July 31, 2017 Author Share Posted July 31, 2017 I just pulled one of my spark plugs from the car the plug is a champion RJ12C I did not see it on a cross reference list for a AC R45 although I did not see it on the cross reference list is the champion RJ12C also a correct plug for the car? Link to comment Share on other sites More sharing options...
MCHinson Posted July 31, 2017 Share Posted July 31, 2017 A Google search for cross references for Champion RJ12C shows AC45 as well as the AC46 on the list. http://www.sparkplug-crossreference.com/convert/CHAMP_PN/RJ12C Link to comment Share on other sites More sharing options...
buick special Posted July 31, 2017 Author Share Posted July 31, 2017 I saw that it shows up on a cross reference for a AC 46 but someone posted the spark plug for the car was an AC R46 and it does not show up in that cross reference so I am confused? is an AC R46 correct for the car or an AC 46 Link to comment Share on other sites More sharing options...
jvelde Posted July 31, 2017 Share Posted July 31, 2017 AC - 46 was what it came with originally, but no longer is made. The AC - R45 is what many think is the best alternative. Sometimes you can find original plugs at swap meets or on the internet. Link to comment Share on other sites More sharing options...
FLYER15015 Posted July 31, 2017 Share Posted July 31, 2017 Though AC46's are rare, they can be found on e-bay now and then. AC plugs get hotter as the number goes up, so you could use a 47 or a 48 without too much concern. There is also an AC-C49 which is in production and is used quite often in generators. HOWEVER, if you are running a plug cover, you must physically match the length of the replacement plug to the spec'd AC 46. Thread depth and insulator height must match also. Ask me how I know............ Mike in Colorado 1 Link to comment Share on other sites More sharing options...
Spinneyhill Posted July 31, 2017 Share Posted July 31, 2017 The R46 is a resistor spark plug, the same heat range as the 46. Resistor plugs incorporate a ceramic resistor to suppress ignition noise generated during sparking. Resistor spark plugs prevent electrical interference that can disrupt car radio reception, two-way radio and cellular phone operation. This type of spark plug also prevents electrical noise from interfering with the operation of the computer in the engine, should your 1940 Buick ever have one installed! 2 1 Link to comment Share on other sites More sharing options...
buick special Posted August 1, 2017 Author Share Posted August 1, 2017 Posted 15 hours ago Though AC46's are rare, they can be found on e-bay now and then. AC plugs get hotter as the number goes up, so you could use a 47 or a 48 without too much concern. There is also an AC-C49 which is in production and is used quite often in generators. HOWEVER, if you are running a plug cover, you must physically match the length of the replacement plug to the spec'd AC 46. Thread depth and insulator height must match also. Ask me how I know............ Mike in Colorado Thank you for the tip , I found the original sheet metal covers for the spark plugs in the trunk would the plugs I have in the car (champion RJ12C ) which cross reference with the AC 46 fit in w/ no problem? would the AC R46 fit in w/ no problem? Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 1, 2017 Share Posted August 1, 2017 I would guess that they are the same and the Champion plug is a resistor plug. No problem using that plug IMO. Link to comment Share on other sites More sharing options...
Dave39MD Posted August 1, 2017 Share Posted August 1, 2017 Measuring from the base where the gasket sits on the plug to the tip; Green Stripe made by AC R46 - 2.236 44 (should be the same as 46) - 2.236 Currently available ACDelco R45 - 2.496 Vintage of the car AC 46 - 2.202 You can get the current ACDelco at most any parts outlet. The green stripe plugs seem common on ebay, the stripes are around the insulator. Hope this helps 1 Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 3, 2017 Share Posted August 3, 2017 (edited) The green stripes are older plugs. The green stripes which were called "fire ring" plugs. The green stripes were discontinued because if there was any variation in the rib the green would not print correctly and show a void. To eliminate the appearance variation the green stripe was discontinued. No difference between green stripe and no stripe as long as the number on the plug is the same. The most important thing when installing spark plugs is to USE A TORQUE WRENCH! If you tighten the spark plug over specified torque you will have the plug running colder than designed and possibly have a plug that would foul. Not tight enough the plug would run hotter and you could either have the tip of the plug burn off and / or burn a hole in the top of an aluminum piston or other damage. I worked for AC for a number of years including building millions of plugs while I was going to school. Edited August 3, 2017 by Larry Schramm (see edit history) 1 Link to comment Share on other sites More sharing options...
Terry Wiegand Posted August 3, 2017 Share Posted August 3, 2017 Larry, where does one find the torque values for seating the plugs? I don't believe that I have ever seen anything to that end contained in the plug box when installing new plugs. Terry Link to comment Share on other sites More sharing options...
buick special Posted August 3, 2017 Author Share Posted August 3, 2017 I went and bought another champion rj12c , which directly cross referenced to an ac46 when I asked him to bring out an ac R46 and compared it to the champion rj12c the electrode was much higher almost 3 x which means it would go in deeper into the cylinder so rather then get an unknown I stuck with the champions that were already in the car Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 3, 2017 Share Posted August 3, 2017 2 hours ago, Terry Wiegand said: Larry, where does one find the torque values for seating the plugs? I don't believe that I have ever seen anything to that end contained in the plug box when installing new plugs. Terry Look in the service manual. The spec is usually there. If not, a quick google search of spark plug torque will find a lot of charts for different size plug with and without a gasket(tapered seat). You can look here. https://www.google.com/search?biw=1280&bih=623&tbm=isch&sa=1&q=spark+plug+torque+chart&oq=spark+plug+torque+chart&gs_l=psy-ab.12..0i24k1.308795.308795.0.311103.1.1.0.0.0.0.141.141.0j1.1.0....0...1.1.64.psy-ab..0.1.140.kegHY5AGSno Link to comment Share on other sites More sharing options...
Dave39MD Posted August 3, 2017 Share Posted August 3, 2017 I am not sure about the cross, my AC book shows RJ12C crossing to C49. C49 would be beyond the heat range recommended by the manufacturer. What exactly on the plug is 3X times longer? Hot plugs, like a 49, have been know to melt holes in pistons. I have more books and will check further but I would use what the manufacturer recommended. Dave Link to comment Share on other sites More sharing options...
buick special Posted August 3, 2017 Author Share Posted August 3, 2017 Report post x #1 Posted Monday at 08:50 AM here is the cross reference list from the web AC DELCO 46 - Alternative spark plug Replacement spark plugs for AC DELCO 46: Brand Model Accel 124 Autolite 295 Autolite 297 Autolite 306 Autolite 458 Bosch 0241225548 Bosch W9EC Bosch W9EC0 Bosch WR9EC Bosch stk 7515 Champion J11 Champion J11C Champion J19LM Champion RJ12C Champion stk 511 Champion stk 592 Champion stk 861 Denso 6004 Denso W9-U Denso W9U Denso stk 6004 Eyquem FS20 General Motors 1559494 Iskra FS20 Lodge BAN Motorcraft A11 Motorcraft A11LM Motorcraft AS8 Motorcraft stk 117 Motorcraft stk 77 NGK 3110 NGK 3210 NGK B-4 NGK B2 NGK B2-10 NGK B4 NGK stk 3110 NGK stk 3210 Prestolite 14-09-01 Splitfire SF045F Torch G4C Link to comment Share on other sites More sharing options...
Dave39MD Posted August 3, 2017 Share Posted August 3, 2017 I am using factory (AC) books. Let me check the cross in a few more but again I would use the AC plugs recommended. Link to comment Share on other sites More sharing options...
Dave39MD Posted August 3, 2017 Share Posted August 3, 2017 Checking an old Champion catalog the cross for AC 46 is Champion # J11C. There is danger in using cross reference info for application. Hope this helps. Dave Link to comment Share on other sites More sharing options...
buick special Posted August 4, 2017 Author Share Posted August 4, 2017 very confusing A Champion # J11C. plug whose cross reference is Champion # J12C. whose cross reference is Champion # RJ12C. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 4, 2017 Share Posted August 4, 2017 2 hours ago, Dave39MD said: I am not sure about the cross, my AC book shows RJ12C crossing to C49. C49 would be beyond the heat range recommended by the manufacturer. What exactly on the plug is 3X times longer? Hot plugs, like a 49, have been know to melt holes in pistons. I have more books and will check further but I would use what the manufacturer recommended. Dave A C49 spark plug would be a very hot spark plug. The C would indicate that it was made for a commercial application like maybe a generator or route delivery truck. 1 Link to comment Share on other sites More sharing options...
buick special Posted August 4, 2017 Author Share Posted August 4, 2017 I defiantly do not want to use something bad for the engine but all the cross references I have checked say a champion rj12c (also called a champion 592 ) is the correct replacement for the ac 46 the ac R46 is not even on the cross reference for the ac 46 and I compared the electrode tip of the ac r45 that produces the spark as much taller (goes in deeper) than the champion rj12 c which looks physically identical to the ac 46 let me ask this to everyone please post replies anyone else using a champion rj12c ( or champion 592) , how long have you been using them and how well do they work anyone using an ac R46 (not the ac46) , how long have you been using them and how well do they work Link to comment Share on other sites More sharing options...
Pete Phillips Posted August 4, 2017 Share Posted August 4, 2017 How many R46 plugs do you need? Other old sizes, too... $2 each. Pete Phillips, BCA #7338 Leonard, TX 1 2 Link to comment Share on other sites More sharing options...
MCHinson Posted August 4, 2017 Share Posted August 4, 2017 You have heard a number of experienced Buick drivers give you their advice. The plugs suggested by one of the major old Buick parts suppliers is: http://bobsautomobilia.com/electrical/spark-plug-1938-1942-1950-53-.-ac-r45/ I have used them for a while in my 1937 Century with excellent results. I trust their recommendation. The Chassis Parts Manual shows 46 as the original plug number for your 1940 Buick. Pete Phillips, a respected Buick expert and editor of the BCA magazine, has offered to sell you a set of AC R46 plugs even cheaper than Bob's sells the AC R45s. You have two excellent economical choices to choose from there. The "R" on a plug means it is a resistor style plug. When the car was new, I don't think they had figued out how to manufacture a resistor plug, but your car will be fine with resistor or non-resistor style plugs. With non-resister style plugs, you will have more of a chance of unwanted ignition noise interfering with radio listening or perhaps cell phone use in or near the vehicle. Link to comment Share on other sites More sharing options...
buick special Posted August 4, 2017 Author Share Posted August 4, 2017 Thank you all for your help , time and patience with a newbie just to confirm everyone here uses an AC R46 plug in their straight 8 motors with no exception and have used them for years with no problem to the engine Link to comment Share on other sites More sharing options...
Dave39MD Posted August 4, 2017 Share Posted August 4, 2017 No, that is not what we have been saying. The currently available AC spark plug is R45 and is available at Bob's and many of your local parts sources. R46 will have to be sourced from members as offered above or ebay type sources. R46 is a good plug, just not as easy to acquire as R45. Dave Link to comment Share on other sites More sharing options...
buick special Posted August 4, 2017 Author Share Posted August 4, 2017 ok , I just want to use what everyone else is using I can not get an AC 46 locally as it is discontinued but I can get an AC R46 from someone I know locally if everyone is using an AC R45 perhaps I should get that instead I only want to buy a plug that everyone else is using and has been for years so I know it has a track record of being safe for the straight 8 motor Link to comment Share on other sites More sharing options...
MCHinson Posted August 5, 2017 Share Posted August 5, 2017 Any of those three will work just fine in your Straight 8 Buick. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 5, 2017 Share Posted August 5, 2017 2 hours ago, buick special said: ok , I just want to use what everyone else is using I can not get an AC 46 locally as it is discontinued but I can get an AC R46 from someone I know locally if everyone is using an AC R45 perhaps I should get that instead I only want to buy a plug that everyone else is using and has been for years so I know it has a track record of being safe for the straight 8 motor The item to be concerned with when choosing a spark plug is the HEAT RANGE which in this case is a 45 or 46. If it has nothing, a C, or an R in front of it will have not affect on the performance of the sparkplug. It could also be a LM45 and it will perform the same. The LM plug is designated for a lawn mower and usually will have a screw top to connect the wire to. Just a different top. An AC 45 will give you the same performance as a R45. Period. That is as long as you TORQUE the spark plug to the specified torque specifications. 1 Link to comment Share on other sites More sharing options...
Guest Posted August 5, 2017 Share Posted August 5, 2017 If there was a problem with newer plugs being too long to fit under the cover would an LM plug not be the one to use. I seems to me that they are shorter. Personally, from my experience, I would never use and AC or Champion plug if I could get an NKG. Link to comment Share on other sites More sharing options...
MCHinson Posted August 5, 2017 Share Posted August 5, 2017 6 hours ago, Tinindian said: If there was a problem with newer plugs being too long to fit under the cover would an LM plug not be the one to use. I seems to me that they are shorter. Personally, from my experience, I would never use and AC or Champion plug if I could get an NKG. There is not an issue with the 45 or 46 being too long to fit. The AC R45 fits perfectly and the AC 46 was the original equipment used by Buick. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 5, 2017 Share Posted August 5, 2017 (edited) Ok, let me do some show and tell. The first picture shows four different spark plugs that are heat ranges from 41 to 49 and have regular thread except the last one which is a R45S. The S designates that the plug has a small "skirt" below the threads. The threads do not immediately start at the bottom of the plug. The only differences between the plugs is the heat range, the connection at the top of the plug which is called the screw, and the color of the printing on the insulator. The difference in the heat range in these examples would relate to the particular application. The LM49 spark plug because it is a hotter plug would probably be used for a 2 cycle lawn mower that uses a gas/oil mixture and would have a tendency to foul out and the hotter plug would minimize that possibility. The picture below is of a cut away of a sparkplug insulator and shell. This insulator starting from the left has the tip. This could be made from a special steel as in "traditional" sparkplugs or newer plugs have much smaller platinum tips for longer life. Moving to the right, the dark area is the resistor material that gives the plug the "R" designation. If the plug is not a resistor plug, then a fine powder like steel is put into that space. The non resistive material would have the same general color as the tip and screw. The next thing that you see is the bottom of the "screw". The "screw" will change configuration depending on the particular application. LM/SP, etc. When the plug is assembled the insulators are in a tray vertically. The tip is dropped into the insulator. Next the powder charge is added. It would be resistor or plain metal. This material is also the seal to keep combustion gases from leaking from the tip of the plug to the top of the insulator and leak past the screw at the bottom of the screw. Next the screw is added to the assembly. When the parts of the plug are first assembled the screw sticks up above the top of the insulator about 1/2 inch (10mm). The whole assembly is then put into an oven where it is heated up RED HOT and glows. When the assembly get hot it is then put into a press and the screws are pressed down into the insulator so the bottom of the screw is sitting right on top of the insulator. It is then sent to a cooler to cool down slowly. NOTE: If you look carefully at the top center of the insulator you will see a small groove where the insulator meets the shell. This is the designation used internally for the heat range of the particular insulator. Different heat ranges have a different number of grooves or out ribs. The insulator is now complete and ready for final assembly. This particular plug is a heat range 45. If it was a hotter plug the tapered end of the insulator would be thinner and if it was a colder plug that area around the tip would be thicker/fatter. The thinner tip does not allow the heat at the tip of the plug to be drawn from the tip to the shell to the head as fast as a thicker insulator tip. The thickness of the tip end determines the heat range of the spark plug. If you need any more information, let me know. I made millions of these while going to school. Edited August 5, 2017 by Larry Schramm (see edit history) 6 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 6, 2017 Share Posted August 6, 2017 (edited) Close, according to AC Delco, the S is extended tip. That's what I observed years ago with R44S plugs vs R44 plugs. The Corvair used FF suffix plugs, and when they becme unavailable, AC made F suffix, which also has the "starter' unthreaded area like the S in your picture. I like your description of how they are made. Edited August 6, 2017 by Frank DuVal (see edit history) 2 Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 6, 2017 Share Posted August 6, 2017 (edited) Frank, If you look at your picture above, there is an area below the threaded part that does not have any threads. This is what I am calling the skirt. Plugs that do not have an "S" in the numbering do not have that unthreaded area. Thanks on the description comment. Edited August 6, 2017 by Larry Schramm (see edit history) Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 7, 2017 Share Posted August 7, 2017 I got a better picture of a 44S and attached it. I also attached a picture of R44F. They look to have the same starter missing threads to me. But, maybe the S unthreaded area is slightly longer.I would include a picture of a non suffix 44, but most everyone knows they have threads all the way to the end of the shell. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 7, 2017 Share Posted August 7, 2017 8 hours ago, Frank DuVal said: I got a better picture of a 44S and attached it. I also attached a picture of R44F. They look to have the same starter missing threads to me. But, maybe the S unthreaded area is slightly longer.I would include a picture of a non suffix 44, but most everyone knows they have threads all the way to the end of the shell. Frank, After this discussion I would hope that everyone knows that the S designated plug does not have thread all the way to the end. Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 7, 2017 Share Posted August 7, 2017 And on the S suffix the Tip extends further out from the shell. The length from the gasket surface to the electrode is longer on the S plug. I just wanted to show that the F suffix is also unthreaded, just like the same place on the S suffix. I also hope they also learned that the number is only heat range on AC plugs, and the suffix can be important. But have we taught them that AC in AC Delco is the same Champion as in Champion plugs? Albert. Link to comment Share on other sites More sharing options...
Larry Schramm Posted August 7, 2017 Share Posted August 7, 2017 (edited) Albert Champion was brought over from France by Billy Durant to make spark plugs. They shortened the company name from Albert Champion spark plugs to AC Spark Plugs. My understanding that there was an issue between Durant and Champion and Albert left AC and founded a new company called Champion spark plug company. AC Delco is just a marketing name put together when GM was creating Delphi and the component company Delphi. AC without the AC name became a non entity when Delphi tried to sell spark plugs and other components under the Delphi name. No brand recognition in the aftermarket. Edited August 7, 2017 by Larry Schramm (see edit history) Link to comment Share on other sites More sharing options...
Dave39MD Posted August 7, 2017 Share Posted August 7, 2017 (edited) Larry, ACDelco was around long before Delphi. It started as United Motors Service Corp in 1916 and in the 1960's became United Delco. AC wanted to go their own way and did for a period of time then in 1974 AC and Delco merged their sales forces and warehousing. They celebrated their 100 year anniversary last year. I guess we are getting away from the op's question. Dave Edited August 7, 2017 by Dave39MD (see edit history) Link to comment Share on other sites More sharing options...
buick special Posted August 7, 2017 Author Share Posted August 7, 2017 2 hours ago, Frank DuVal said: And on the S suffix the Tip extends further out from the shell. The length from the gasket surface to the electrode is longer on the S plug. I just wanted to show that the F suffix is also unthreaded, just like the same place on the S suffix. I also hope they also learned that the number is only heat range on AC plugs, and the suffix can be important. But have we taught them that AC in AC Delco is the same Champion as in Champion plugs? Albert. Thank you all for the wonderful and informative posts Frank , what you posted above may explain what I saw at the parts place I asked the parts salesman to bring me out an AC R46 plug when he put it on the table and opened the box I saw immediately that the metal that bends over the electrode came out further Then the champion rj12C that I brought with me for comparison when they were side by side That got me worried which is why I kept the champion and had started the original post now when thinking back to that day I recall moving the AC box and believe it had several letters after the R46 and believe one may have been an S so I am thinking now he did not bring me the correct R46 plug I will go back there In a few days to check on this Link to comment Share on other sites More sharing options...
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