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Re: dumb spark plug question(s)

|Got a real dumb question for y'all. Actually a couple. Well, this could |turn into many. Anyway... I've been trying to compile a list of spark |plug numbers for various old cars. Only thing I have to go on is some |old Champion numbers from the shop manuals, and some of them are |obsolete. Now I'm having a real hard time finding one authoritative |cross reference guide online and indeed the only semi-complete one I've |found is published by NGK, nothing available for Champion, Autolite, or |Bosch (the three brands I use/can commonly find locally.) I kind of |understand this as they'd rather you look up your parts by application |and not find the part numbers for three other mfgrs. as well, but |Autolite is the only company that will allow me to look up the vehicles |in question on their web site. (d'oh!)

|I'm getting an education on how much I don't know about spark plugs. Is |there any sort of magic decoder ring to understand the part numbering |systems used by various mfgrs.? I gather that the first letter of the |Champion part numbers has something to do with reach and thread (and |possibly seat type) and Autolite has a sketchy explanation on their web |site but doesn't break down what all the digits mean. What I'd really |like is something that would enable me to say "hey, I'm using a Bosch |W8DC and it is physically the right plug but I think I need one a step |hotter, that would be a XXXX" does such an animal exist?

You need to get the printed catalogs from each manufacturer. Each has a breakdown on what their numbering system means to the physical characteristics of the plug. Each has an interchange in the back. Suck up to the guys at your local parts store and maybe they will get you one, or at least give you the old one under the counter.

|Another thing that I am being forced to think about is the difference |between resistor and non-resistor plugs. What is the purpose of having |a resistor in the plug? I never thought much about it before now but I |ASSume the plugs I'm working with are all non-resistor and one of the |cross references I came up with for one of the numbers was an AC R44XLS |and I always thought the R in an AC number was for resistor - correct?

Right You do need to know that NGK plugs get colder as the number gets higher, all others work the opposite. Also, since the advent of copper-core plugs, heat ranges are much wider than they used to be. Changing heat ranges is not to be taken lightly, especially going hotter.

|What are the downsides of using a resistor plug in an engine that |originally came with non-resistor plugs? These are all conventional |breaker-point ignitions, if it makes a difference. I am running modern |7mm suppression core wires on all my cars.

Radio static is the main reason. In computer cars RFI is also a factor.

|Finally I feel like I'm accomplishing something by being anal retentive |about this. I just bought some new Bosch W8ACs for one of my cars that |originally spec'd a Champion H14Y. Turns out the W8AC is a 1/2" reach |and the H14Y is a 7/16." That's what I get for trusting some web site |:) actually the W8AC works fine but I'm worried about the threads |protruding into the chamber and causing hot spots. Granted with 8ish to |1 CR detonation probably isn't a HUGE deal but it can't hurt to do it |right. Will have to pull plugs and check thread length to see which |works better.

It's a problem. If nothing else, the protruding threads will have deposits on them which will be bad for the threads when you take it out. I'd change them immediately, and carefully.

| |whatever. any help greatly appreciated. If there's a web site that |covers all this I'd appreciate a pointer, because my googling skills are |about exhausted and I still feel rather clueless. | |thanks | |nate | |PS - FWIW these are the numbers I have and would like to be able to buy |new equivalents | |J7 |H11 |H10 |H18Y |H14Y |J12Y |N8-67B

Most you can just add a C to the end for copper core ex. H10C Some may only be available in resistor ex. RJ12YC the Y indicates extended tip The J indicates short 14mm threads The H indicates short 18mm threads, tapered seat IIRC

email me directly and I'll get a catalog and cross those numbers for you.

Rex

Rex in Fort Worth

Reply to
Rex B
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snipped-for-privacy@REMOVEtxol.net (Rex B) wrote in message news:...

That's about what I figured. I did bid on some stuff on eBay that seems reasonably priced. I can try one local parts store that might have that stuff, but they seem to *keep* all their old books, which is a habit I encourage.

thanks, that's something else I didn't know. I was expanding the list a little last night as the parts books list several different plugs for some vehicles and I assumed that they were alternate heat ranges but I didn't know which were hotter and which colder.

The resistor plugs reduce static/RFI? Well that's something for me to consider since I do have a radio in both my old cars and both are fairly unlistenable with the engine running. (stock AM only - and to add insult to injury the trimmer screw is busted on my '62) I have all three filter caps on my '62 and I still am getting a decent amount of ignition pop - does not appear to be picking up noise from generator or regulator, it's all very regular and it pops, not whining. Does using the resistor plugs have any measurable negative effects on engine performance? Which would be preferable if I went to a Pertronix Igniter or maybe a Chrysler ignition box setup down the road? ISTR noticing a resistor plug being listed as an alternate for the '62 in the parts book.

Good point, I didn't think of that. I actually have not taken the car for a spin since I changed the plugs and oil, just twiddled with the idle mix a little.

I'll do so when I get home (on a snack break at work right now) and thanks much for the explanations and offer.

By way of explanation, those part numbers are for 1956 to 1964 Studebaker engines, and most local parts stores don't have books going back that far, and I was also just trying to compile a resource for other Stude drivers since this info doesn't seem to be readily available on any of the big Stude web sites. I've also done something similar for oil and air filters - I guess it's just a typical Stude owner trait, we're all too cheap to spend big bucks for the absolute correct filters, plugs, etc. when they're just going to have to be replaced again in a year or two. It's nice to be able to go into Crap Boys with a little piece of paper from your glovebox and just tell the guy what you need rather than having to go through the "well, our computer doesn't go back that far, and we only have books from when this store opened in 1989..." and then you can take advantage of all the good sales etc. Finally when was the last time you bought a 40 year old car that had all the correct stuff on it? Sometimes what's in there is WRONG - I bought a used Packard engine a while back that had spark plugs with three different reaches in it! and sometimes even the books are wrong - took me quite a while to find a correct air filter for my '62 as the one my (usually good) parts store gave me didn't fit, and the old filter was, well, old and had no discernable part numbers on it. (yes, I know it had the correct filter housing on it as it was parked in 1968 and I also have several other identical housings laying around.) I happen to be anal retentive enough that I hate blindly trusting the numbers someone feeds me and also as you can see above the statement "well I used a W8AC with no problems" may be somewhat misleading... and above all I *hate* looking at a list of part numbers, knowing that there's a code that explains it all, and not knowing that code :)

sorry about this post getting out of hand... back to your regularly scheduled tech discussions...

nate

Reply to
Nate Nagel

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