If I go to the counter of a car parts store and I ask the counterman for a spark plug one or two heat range hotter than the one I have should he be able to go to a book and find a graph telling him the coldest to the hottest in that plug. In the "old days" I could just ask for a little hotter or cooler and the counterman would go back and bring them out. The last few times I went they had to spend time back there opening boxes to try to find something. Come on you experienced counter guys/gals give me some insight. Thanks Gary
BUT.....In the "old days"everything was done by a catalog page ,not a computer screen.. todays counter men probably could not read a catalog.
I am my own "parts counter guy". I use the "order /pay online" & pick-up in store method offered through O'Reilly auto's website. Walk in, say your name, and they hand you a bag. They are good at handing you the bag and that's all I need them to do.
HAHAHAHHA - The answer will be Year, Make and Model, Does it have A/C, followed by What's a heat range. Parts book these days, that's rich. Sorry, for being a smart ass - but unless you have a really good old school parts store with a grey beard, You better plan on doing the research yourself -
So I walk into a "chain" auto parts store. I ask if they have snow brushes. The kid behind the counter asks "what kind of car"? I answer "white". "and the Beat Goes ON, and On, And On"! KK
i have a good young guy at my local advance auto store, who knows how to actually look for the books they all get, and has looked up and ordered diff heat ranges for me. i know what you mean, its pretty anoying now a days.
Maybe. Best to do your homework online, and know what you want, part # wise. Different manufacturers have different methods for numbering heat ranges. Some, like Motorcraft, go down as heat range gets colder. NGK runs the other way iirc. And manufacturers have consolidated their lines, so the plug number may be unobtanium at this point, or special order. They can't really afford to stock oddball stuff.
I was trying to get points for the dual point set up in my '56 Hemi, the kid at the counter needed to know the body style, so I said Chrysler 300, then he says, two or four door, so I said two door... after a couple of minutes of him on the computer, I said to him, Oh yeah, forgot to tell you it has whitewalls....he said good info.......then I walked!
I know it is a dumb question but then I am a dumb guy. Below is what my AP 847 plug looks like. Not bad but I like a little lighter. Would 848 or 849 be hotter?
I have to agree with Truck64. Go to the manufacturer's website and research it yourself. There should be interchange info there too.
I am one who also likes to do my own research and then go into the store and give them a part number and in many cases I have checked availability for the part I am after on the store's website. The only thing the counter people need to know these days is how to check the boxes on the computer. The last time I went to a parts store unprepared I was asked if my 62 Impala was rear wheel drive. No shit.
You're already running the hot plug Autolite offers in that size of plug. Check page 2 at this lionk here: http://www.autolite.com/Productfinder/Resources/Heat Range/Heat_Range.pdf Also, this is good for general information: http://www.autolite.com/media/14882/technical_training_manual.pdf
I was gonna ask why you wanted a colder or hotter plug. You're not a dumb guy, it's a good question. Lots of people think a colder or hotter plug is the remedy for a fouled or blistered plug. GENERALLY speaking, the manufacturers standard heat range will provide satisfactory service. What you want to do, is dial in the carburetor jetting, power valve if utilized, accelerator pump shot etc. Make sure Ignition is squared away before carb tuning. A colder plug is indicated when racing for example, or extended highway runs. BUT, they aren't changed for jetting reasons, or fouling, as such. Very common misconception.
Heat Range The term Heat Range refers to the speed with which a plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or race car, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. 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 that cause fouling. The spark plug design determines its ability to remove heat from the combustion chamber. 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, keeping 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 adding a turbo or supercharger, increasing compression, timing changes, use of alternate fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature, necessitating a colder plug. 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. For example, 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 Champion, Autolite and Bosch, the higher the number, the hotter the plug. For NGK, Denso and Pulstar, the higher the number, the colder the plug. It is not recommended that you make spark plug changes at the same time as another engine modification, such as injection, carburetion or timing changes. Performing too many modifications or tune-ups at once will lead to misleading and inaccurate conclusions if any issues occur (an exception would be when the alternate plugs came as part of a single pre-calibrated upgrade kit). When making spark plug heat range changes, it is better to err on the side of too cold a plug. Running too cold a plug can only cause it to foul out, whereas running too hot a plug can cause severe engine damage. ACCORDING to AutoLite's photo reference that plug is about dead on for today's unleaded gas - maybe a hair rich. And best I can find there is no such plug as an AutoLite AP 848 or 849
I see now it is not as easy a question as it was in the '50s and '60s. So many more potions. I probably should just leave well enough alone and be happy it is running as well as it does with 4 old 97s, open plentum manifold, Isky. roller tappet cam, on a 67 year old engine. Gary
i can't count the number of times i've been asked for hotter plugs because they are going "racing"...
http://www.sparkplug-crossreference.com/convert/autolite/AP847 the rj18yc6 the 18 is as hot as they come... Details about Champion RJ18YC6: Threaddiameter: 14mm Threadreach: 9.5mm Seattype: flat Hexsize: 21mm Tipconfiguration: projected Construction: Standard construction Terminaltype: Solid
Another thing that makes it more difficult for a counterman to select plugs by heat range is that pretty well all of the spark plug manufacturers are now using different stock numbers for the plugs than the old numbers on the plugs themselves. For instance, Champion RF11YC is now a "22", NGK UR4 is now a "6630", etc. I have not bothered to research into whether this new numbering system can be used to imply heat range, but it doesn't look likely on first glance.
Those are both pretty hot plugs. If I had to run that hot a plug I might consider a couple things. If you had enough spark like a MSD or any electronic ignition. If I had enough timing in the engine Or if I would drop one jet size. If you were running a RJ-8 and needed a little heat going to a 12 would be an option but going from a 12 to an 18 is pretty hot. Just my opinion. Sent from my iPad using The H.A.M.B. mobile app
Hate to say it, but get yourself a wideband O2 sensor for carburetor tuning. The guys who have been reading plugs for a while maybe don't need one, but they eliminate a lot of "guess and by golly" for most of us. Plug evaluation is a lot more complicated than I thought.
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