[DeTomaso] Plugs (long)

[JDeRyke at aol.com]

Everyone is an 'expert' on air filters, oil filters and sparkplugs, and 
this is my opinion: its free and one gets what one pays for.... 
A plug's brand name means nothing. Ford Motor Co does not make Motorcraft 
sparkplugs, and Motorcraft plugs are not specific to Fords. The heat range of 
a plug and its 'reach' are far more important than who made it. Plugs are 
made, cheaply, in the millions per year in large factories- some 'offshore', 
and they all work after a fashion in some engines. And in other similar 
engines, they work terribly. Aluminum heads are thicker so take a longer 
threaded section ('reach') than stock iron heads, and the plug heat range of 
aluminum heads also will be different. In my SVO-Cleveland heads, I use AC plugs 
spec'd for a Corvette 'cause they fit and work well. My friend's Lambo Miura 
ran well on Hitachi sparkplugs made for god-knows-what engine.
I note that you, like about everyone else I know, have a unique blend of 
aftermarket parts in your 351-C. So the plug gap that works best for your 
engine, with your cam, compression, carb, ignition system, local fuel and your 
personal driving habits, must be found by trial and error. Fortunately, 
non-racing plugs can be regapped easily. Once found, expect the 'perfect gap' 
specs to change rapidly, as plugs age, electrical resistence changes and fuel 
quality varies daily. Nothing lasts very long when tuned near its peak. 
As I mentioned, I've seen brand-new plugs that had no gap at all when taken 
out of a package. Others had ground lugs bent sideways. I would never 
blindly screw any plug into any engine without first checking the gap. And I 
would not be surprised if a brand new plug misfires out of the box, given the 
numbers of ways a $4 plug can fail. Give it Smokey Yunick's famous 'flotation 
test' in the nearest body of water, maybe curse a little if it makes you 
feel better, add another plug and go on with your life.
FWIW, I have two well used plug gappers. The one I use now is a 
chromed-steel disc made by Champion sparkplugs in the '80s (p/n CT-481) with a 
graduated edge that gets progressively thicker and is used to simultaneously bend 
and gap an electrode in the range of 0.020 to 0.100". Embossed on the back is 
a metric-to-SAE conversion scale. I also have a plastic disc made by 
Autolite in the '50s, with a protruding notched metal lever that grips a ground 
electrode and bends it. There is a magnifying lens in the disc's middle to 
practice the lost art of 'reading plugs'. There are a series of wire feeler 
gauges around the edges to check the gap. This one's range is 0.020" to 0.040" 
in 0.005" increments, befitting a time when points 'n coils were all that we 
had. Both are the size of a 50¢ piece and are convenient to carry on a 
keychain.

As an aside, special electrode plugs in a street car are another way of 
separating you from your money with little real benefit. Multi-electrode plugs 
were used in ancient DC-3 aircraft in the 1930s as an aid to reliability 
where changing a shorted plug was inconvenient (like, at 10,000 ft in a 
snowstorm). This seldom happens to passenger cars except in Colorado. Good luck, 
all- J Deryke


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