Spark plug recommendations

[Povertycove]

Could anyone help me with recommendations for spark plugs for my 1927 series 11 boattail runabout, and for my 1931 series 15 convertible coupe? Modern replacement plugs are on the cold side, especially the Champion w18s. I'm guessing that both cars could use hotter plugs, and I think for touring, Autolites work best. Any advice?

[odyssey]

For engines in good shape and good tune, the w18's works great in the series 11 and D16 or currently 516 work very well in the side drafts. You can run a W16 in the series 11, but the side drafts will not favor a hotter plug. I have had such good luck with champions in the series 10 and later cars that I have not tried another plug. I replaced the D16s in my 153 after 25,000 when the gaps got so big it misfired on full throttle!

Surely others work well too, but I have not tried them.

Tom Rasmussen

[Povertycove]

The w16s seem to do much better in my series 11 than the w18s. I've been told by a very knowledgeable source that modern w18s are actually colder than originals. I am going to try running Autolites 3077s to see if that wil improve ignition.

[RansomEli]

Let us know your results. I've been running W18s for years with no problems, although I seem to prefer the older versions over the modern plugs. Like fine wine....

[odyssey]

Yes, please let us know. I have not yet learned why some engines are more sensitive to plugs than others. It seems the downdraft and later Franklins are not fussy, but the earlier the Franklin the more difficult spark plug choices are. On my 1913, I have to run HOT plugs while touring with slow cars (30 mph max) or they foul. I have to run colder plugs for high-speed work (40 - 50 mph) or I sense pre-ignition and a loss of power at high loads & speeds even though the carb mixture is fully dash adjustable.

Different makes of plugs also run totally differently. Why won't a Champion plug work well in a Packard Twelve (AC's are the choice), yet an AC plug does not seem to work in a Straight 8 Buick?

I am struggling to find a pipe thread plug for my 1910 that fires smoothly at light loads (a characteristic Franklin problem on the magneto models into 1916). I had a 1911 G that had thread reducers in the spark plug pipe thread and could run any modern plug (I don't recall what I used, but it was a hotter range plug). That car ran perfectly at all speeds & ranges. I really don't want to run modern plugs in my early cars now, I just like the look of the original plug and they are so visible - even right through the front grill.

So am on the hunt for better plugs. All info is helpful!

[Povertycove]

Not to change the subject, but the fact that your '13 does 40-50 mph seems remarkable to me. For brass touring I drive either a 1914 Saxon roadster (35 mph) or a 1915 Saxon touring six (40 mph). I had never thought of the Early Franklins as on par with the P's, Cadillacs and other fast cars. I'm looking forward to my first Trek this year. I have a lot to learn about Franklins.

[Guest richentee]

This was Bob Barrett's suggestion at last year's Tech session, grinding down the sides of a 1/2" pipe plug to have it run hotter.

[Povertycove]

I'm not sure I understand what was done here. Is this a w-18 that has had some extension made to the sparking wire?

[Steve Braverman]

From what I understand about spark plugs, I don't see how Bob's modification will work. I always thought it was the length of the porcelain that determined the heat range.

[Guest richentee]

The plug is not a W series plug. It is a 1/2" pipe thread Champion. They are used on earlier Franklins (such as my 1906 G). They suffer from carboning up from a combination of circumstances, including the method of lubrication on the cars.

What Barrett has done is to grind away all of the unthreaded skirt (except the part supporting the ground electrode) that surrounds the porcelain insulator of the plug.

Plug heat ranges, as Steve says, are usually determined by how much porcelain is attached to the metal body of the plug. The more that is attached, the cooler the plug as the heat of the explosions can be more easily conducted away.

By grinding away most of the skirt, Barrett is attempting to make the plug run even hotter than it would normally to aid in burning off the carbon (or perhaps not even allowing it to form in the first place). He is trying to expose more of the porcelain to the heat of the cylinder. He claims it works on his G. I have not done it yet on my cars but will try it on the G this summer.

I raised his example as one attempt to deal with the issue of finding the right temperature plug. If it confused the issue of the W series plugs, you have my apologies.

[odyssey]

Not to change the subject, but the fact that your '13 does 40-50 mph seems remarkable to me. For brass touring I drive either a 1914 Saxon roadster (35 mph) or a 1915 Saxon touring six (40 mph). I had never thought of the Early Franklins as on par with the P's, Cadillacs and other fast cars. I'm looking forward to my first Trek this year. I have a lot to learn about Franklins.

I look forward to seeing you at the Trek. Franklins, while not the most powerful cars on the road, were some of the fastest. It's all about Power to weight ratio (and frame/suspension design)

Franklin held the majority of long distance speed records across the country from 1904 until the late 1920's, when paved roads improved driving conditions for the heavier, lesser sprung wet-nosed cars.

My 1905 (12hp, 1,000 lbs) was clocked at 50mph in the late 1980's (stripped down). Today I prefer 30mph.

My 1907 had a factory rated top speed of 50, but it's most comfortable at 35 and I rarely drive it faster, but it will run 35+ up the side of a rocky mountain trail!

My 1910 loves to go. 42hp, (2,700 lbs? I'm guessing) factory top speed was 60mph. I am still getting the bugs out, but I think it will tour nicely at 45+. It was driven on cross country runs in the late 1970's by the previous owner.

My 1913 (the "Little Six" for the year - 30hp, about 2,200 lbs) also loves to go and would run 50+ (I used to cruise at 52mph on the freeways before it became a hazard to do so). Today I love running 35-40, quiet and smooth.

All Franklins seem to be very happy running hard and long. The sixes through early 1916 were especially long-legged and FAST for their day. Unfortunately, comparitively few were built and few survive, making parts procurement an issue.

You will enjoy yours when you get them running to your satisfaction. They are unlike other cars of the period in the same original price class and are tremendous values compared to what other period cars sell for today.

Tom Rasmussen

[Povertycove]

Running Autolite 3077 now, and I'm getting a much better ignition, much better starting while hot. I'll report back when I've gotten a few more miles on the 11B.

[Povertycove]

Just to report that the Autolite 3077s work really well on my 27 boattail (11b). The engine starts immediately and runs, now, without a hiccup. No problem with restarting while the engine has been running for awhile, even in this 90 degree weather weve been having. The engine idles nicely and is just a great improvement over the way it ran with Champions. A lot of my brass car touring friends like these 3077s as well.

[scott12180]

As a point of clarification, both Tom and someone who did not identify themselves suggested that Champion W-16s are hotter than W-18's. Two cross listing charts I have disagree --- the higher the number on the Champion, the hotter the spark plug. W-18's are hotter than W-16's. W-14 is a cold plug; W-20 is very hot. Can someone verify this, or refute this with published data?

Also, does anyone know if the new Champion 518 is the same as their W-18? You can buy 518's --- you cannot buy new W-18's at the local auto parts stores.

--Scott Dwyer

[Franklin31]

Heat Range Conversion Chart

[odyssey]

As a point of clarification, both Tom and someone who did not identify themselves suggested that Champion W-16s are hotter than W-18's. Two cross listing charts I have disagree --- the higher the number on the Champion, the hotter the spark plug. W-18's are hotter than W-16's. W-14 is a cold plug; W-20 is very hot. Can someone verify this, or refute this with published data?

Also, does anyone know if the new Champion 518 is the same as their W-18? You can buy 518's --- you cannot buy new W-18's at the local auto parts stores.

--Scott Dwyer

Oops- my error. Yes, the 518 is the same plug, new number. Your excellent article in the Franklin Service Station did a great job of explaining all this.

Tom