"Morning, Sam. Have some coffee?"
Chief of Police Sam Eldon, whose heavy-lidded eyes
and sagging jowls gave him the look of a sleepy hound dog, folded his length
lazily into a chair.
"Can't do more than poison me," he said, taking the
cup Gus handed him.
"Poison? We're more likely to be bored to death,
Sam. It's been a quiet summer."
"Till last night," returned Eldon. "About four a.m.
the Benton Electronics alarm system went off. It's wired to the station
house, so we were there in three minutes - just in time to see a Ford Sedan
hightail it out of there.
"With Carnahan driving, we took off after it. He's
good, but the other fellow was better. Held 90 all the way to Grover's
Creek, then hit over 100 until we lost him on some curves. But I spotted the
car as we shot past the fork at Route 117.
"When he saw he couldn't lose us, he must have
decided to put on an act. He wasn't doing more than 50 when we pulled him
over.
Then he started to act as if he didn't know what it
was all about."
Gus set down his cup. "Reminds me of last night's
late show. The chase scene was good but the ending was a flop."
"This show isn't over yet," said Eldon. "There was
no loot in the car - the alarm must have scared him off before he got down
to business. But we did find a nice set of tools. He's a hard-looking
character, name of Burke. Says he's a mill mechanic and that he was driving
all night to get to a job in Granton by morning.
"He also says a car zipped past him just before he
reached the 117 fork. I phoned the Granton mill this morning. The people
there never heard of him. And those tools of his could jimmy a door or bust
open a cheap safe as easily as they could be used on mill machinery."
Gus stood up. "Well, now that you've beat about the
bush, what did you come for? Want me to look at his car?"
"No, not his car," said Eldon. "Mine. One of my
boys tuned it last week, and it sure did fine last night. But this morning
when I was doing only 60 it began to knock, and power fell off."
Opening the hood of Chief Eldon's well-groomed
Chevrolet V-8, Gus figured that the man who had timed it had probably left
the distributor loose. It took him only a moment to find he was wrong; the
distributor was securely tightened. The spark knock Eldon described could
hardly be from carbon deposits; Gus himself had ground the valves and
cleaned out carbon six weeks before. The plugs showed no signs of
overheating, the fan belt was tight, and the radiator well filled.
But a stuck manifold heat valve could cause local
overheating that wouldn't show on the dash. Gus checked the valve. It was
free, and stood in the heat-off position normal for a warm engine.
Getting out his electronic plug checker, Gus hooked
up its four leads and switched on the engine. As he opened the throttle to
take voltage readings at high compression, there came the unmistakable,
metallic rattle of a spark knock.
The eight traces on the scope all showed firing
voltage to be in the normal range. No plug gaps were worn wide, nor were any
of the plugs fouled. Gus unhooked the scope, disconnected the vacuum-advance
tubing from the distributor and taped its end shut. Then he connected his
timing light and a tachometer.
At idle, the indicator stood at six degrees before
top dead center. Gus opened the engine up to 1,600 r.p.m. The centrifugal
advance moved the timing up to nine degrees. At 2,300 r.p.m., it shot up to
more than 18 degrees.
"Too much spark advance at high speed," said Gus,
shutting off the engine. "Could be the spark-advance springs have gotten
weak."
"All of a sudden, since five a.m.?"
Gus grinned. "I'll admit springs don't usually
weaken so fast unless they're overheated. This is where gadgets quit and we
start thinking.
So the first thing I'll look for is a little rubber
bumper."
Mystified, Eldon watched Gus remove the distributor
and take it to a bench. Turning up the breaker plate, Gus looked at the stop
pin.
Eldon leaned over the bench. "I don't see any
bumper," he said.
"Because it isn't there." Peering into the casing,
Gus fished out a small rubber fitting. "Here it is. It softened through wear
and fell off the stop pin - maybe your high-speed chase helped shake it off.
Without it, the stop pin was smaller and let the breaker plate advance
several degrees more before the pin hit the slot edge. As the car was
already tuned for maximum high-performance advance, this was too much of a
good thing. You got pre-ignition, a spark knock, and a drop in power. I'll
put on a new bumper and then check out the timing."
Fifteen minutes later the police car was buttoned
up and ready to go.
"Suppose you think you're pretty hot," growled
Eldon, with a wink at Gus's assistant, Stan Hicks.
"There has to be somebody around to set an example
for you public servants," said Gus cheerfully.
"Well, you've given me an idea," confessed Eldon.
"About checking out this suspect's car. We have to book him in 24 hours or
let him go. It's an old trick to use an ordinary-looking car with a real hot
engine in it. You show me that's the case, and I'll charge him."
"Didn't get his license number at the scene of the
crime, did you?" asked Gus.
"No," said Eldon. "But we saw him scrape a fender
in tearing out of the alley. This car has the marks - of course the suspect
says they were made somewhere else, two days ago. Come on, get in and let's
go."
In the courtyard of the station house stood a
three-year-old Ford sedan. The body had been well cared for, right down to
the chrome.
The engine also showed signs of care. Its block was
remarkably clean, oil and radiator coolant clear. But two plugs were newer
and of a different brand than the rest. The carburetor and ignition systems
were standard. Gus could find no sign of a special head or other
high-performance parts.
That didn't prove they weren't there, or that the
standard engine wasn't well tuned and capable of hot performance. Gus
inspected the battery posts, the coil, and the two wires that ran from
its low-voltage terminals.
"Can't we start it up?" he asked Eldon.
The chief nodded to a patrolman, who had brought
the keys. He fired up the engine. It settled into a fast idle.
With his handkerchief, Gus pulled off one of the
plug cables. Taking a wooden pencil from his pocket, he held it near the
plug terminal, then brought the cable end near the other side of the pencil.
Sparks jumped, flared into tiny blue feathers on
the cable side of the pencil graphite, and streaked across to the plug
terminal. Gus stuck the pencil back into his pocket and replaced the cable.
"What was all that?" asked Eldon.
"I don't know about the man," said Gus, "but you've
sure got the wrong car. This one never ran away from you at 90."
"How do you know?"
"It couldn't have," said Gus. "You couldn't push it
over 75. The coil polarity is reversed. This pencil test is an easy way to
show it. If the spark feathers are on the plug side of the pencil, polarity
is okay. But when the feathers are on the cable side, the positive of the
high voltage is connected to the center plug electrodes. That ruins
performance, because it will take much more voltage to fire a plug."
"Don't see why," said Eldon. "Most cars have the
negative battery post grounded, but some have the positive."
Gus grinned. "Makes no difference whether a car has
negative or positive battery ground. The high-voltage polarity should always
be negative at the plug terminals. It boils down to something called
electron emission, on the theory that current is a flow of electrons, from
the negative side to the positive.
"The hotter something is, the easier electrons can
hop off it. The center electrode of a spark plug gets much hotter than the
outside one, which is attached to the shell and loses heat to it. So
for easiest current flow and the best spark, the hot center electrode should
be negative. If you make the outer electrode negative, you're forcing
electrons to jump off a cooler surface to a hotter one. That's like bucking
one-way traffic in the Friday-night rush hour."
"The engine runs, so there must be an ignition
spark," said Eldon.
"Sure, at ordinary speeds. But spark-plug engineers
say it takes up to 45 percent more voltage to fire a plug with reversed
polarity. That cuts down on your voltage reserve. On heavy acceleration,
when compression goes up and it's harder for the spark to jump, you get
misfiring. Same thing at high speeds, when the points can't stay closed
enough to build up a maximum magnetic field in the coil. Sam, this car
couldn't have got away from you, let alone run for miles at over 90."
"Okay, maybe it couldn't. Now what does it take to
reverse this polarity?"
Gus pointed to the coil terminals. "Just switching
around these two wires."
"Maybe he switched them the wrong way while we were
turning around, to give himself an out."
Gus laughed. "This engine's clean, but those
terminals are caked with enough dirt to prove they haven't been loosened in
months. Even if he had time to switch the wires, he couldn't have faked
that. Better let the man go, Sam."
"I had a hunch I should, but I couldn't put a
reason to it. Now you have. Guess that's why I put up with your bum coffee."
"Come around in the morning," said Gus. "I'll have
a fresh pot on."
To his surprise, Chief Eldon did show up for coffee
the next morning, looking as if he hadn't been to bed.
"Busy night, Sam?" asked Gus.
Eldon sipped the black brew morosely. "Had to check
out what you said about that car, Gus, so I drove it. Began to sputter at
55, and never would hit 70. Then I switched those two wires. Made a big
difference. I released Burke. He's probably wondering," concluded the chief,
"why his car runs so much better."
"Too bad the real crook got away."
"Oh, we got a flash about that. A man broke into a
contractor's office upstate, then walked into two patrolmen - with the loot
on him - while heading for his car. Same make and model, but sassed up like
for Indianapolis. Must be the one we chased - that fellow sure didn't have
his ignition switched around the wrong way."
"Guess not," said Gus. "His mistake was trying to
switch around other people's money."
END
