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Second Chance Garage

For the Classic Car Restoration Enthusiast

Second Chance Garage


Second Chance Garage

For the Classic Car Restoration Enthusiast

Second Chance Garage

Second Chance Garage

For the Classic Car Restoration Enthusiast

Second Chance Garage

DR. CRANKSHAFT

Dabney's Buick is a little out of balance.

"Hey, Doc, You in?" screamed the voice on the telphone. Dr. Crankshaft quickly recognized Dabney's voice. "Of course I'm in, how else would I be answering the flippin' phone?" Having just finished his breakfast and settling into his newspaper, the Doctor was somewhat annoyed by the interruption.

"Sorry to interrupt whatever it is you're doing, Doc, but I got a problem and no time to fix it. Can you help?

Doc paused for a moment and said "Maybe", the Doc said intentionally slowly as he usually did when trying to slow someone down. He paused for another moment and said "What seems to be the difficulty?"

Doc's stalling tactics had just the opposite effect on Dabney.

Dabney was frantic. "This afternoon is the 100th Anniversary Buick parade in town. I'm sure you know that there's going to be one Buick from each year represented. Well I supplied the Buicks from 1934, '36, '37, '48 and '52 and I'm driving my '67 GS in the parade. Well I got problems with the '67, and the parade is in 3 hours.

"Ok, Dabney, I'll be right over, give me a couple of minutes to finish my coffee." The thought of any delay caused Dabney to get even more excited. "Thanks, Doc, Just remember the parade is in just 3 hours.

About 15 minutes later Doc drove up and Dabney was even more frantic.

Dabney said in a breathless, frenetic tone. "It keeps throwing belts...I put on one and it throws it....doesn't matter whether it's running fast or slow...just keeps throwing belts...what am I going to do...I have to be at the parade staging area in about 2 hours and I gotta have it running."

"Whoa, Dabney...slow down" the Doctor said. We'll get the problem worked out in plenty of time. Now tell me slowly, exactly what's happening.

Dabney took a deep breath and tried to calm himself down.

"As I mentioned on the phone this 1967 Buick GS 340 is the only one representing 1967 in the parade this afternoon and it keeps throwing fan belts. I'll put one on and as soon as the engine gets to about 2000 rpm the belt pops off. Even when the engine is running slow the belt flops all around and I'm afraid it will overheat while crawling along the parade route," replied Dabney.

"Ok," said The Doctor. He could see the look of panic in Dabney's eyes had subsided somewhat. Doc thought to himself for a moment and he said, "I'm gonna assume you tightened the belt properly and the tensioning mechanism isn't loose."

"That's right," said Dabney.

"Let's see, first things first" said Doc. "You can start by going over there and getting me a cup of coffee...with cream, no sugar....don't worry, we've plenty of time," said Doc anticipating Dabney's anxiety.

Dabney took another deep breath and went over to the coffee pot. He returned to the Buick and handed Doc his coffee.

"Thanks," said Doc. "Let's check one of the belts first. These are the correct ones for the car, right?"

"Absolutely, Doc," replied Dabney. "In fact, this belt here is one of the original belts on the car. It matches perfectly with the replacement belts. All the pulleys are aligned and nothing's loose."

"Well, let's start up the car and look at how the belt tracks," said the Doctor. They made sure the belt was tight and could be depressed less than a half-inch at the mid-point, then started the engine. The Buick came to life and the belt started flopping wildly in the center, just as if it were loose.

"Isn't that interesting?" said the Doctor. "The belt is tight and it still flops. Let's spin the water pump and alternator by hand to make sure my diagnosis is correct."

"You mean you've figured out the problem already, Doc?" exclaimed Dabney.

"Yup, I think so, but let's check out those two possible culprits first," answered a confident Dr. Crankshaft.

They shut off the engine and removed the belt. They then turned the water pump pulley by hand to determine if the shaft was binding up and then did the same with the alternator. Neither showed any resistance.

"That tears it! Your balancer is shot," said the Doctor.

"The balancer? I have to confess, Doc, I'm not sure what you mean. The only balancer on this engine is the harmonic balancer on the front of the crankshaft, but it's solid and tight. I checked to make sure the big bolt holding it on was torqued to specs. How could it cause the belt problem if it isn't wobbling?" asked a slightly bewildered Dabney.

"Great gallopin' gearshifters! You don't really know how the harmonic balancer works, do you Boy," said the Doctor, his voice raising an octave.

Seeing a long-winded explanation coming up, Dabney said "I don't mean to be rude, Doc, but can you keep it short. Remember the parade?"

"Ok, ok," said Doc. "Here's the short version: engines have to be balanced at both ends of the crankshaft to offset power pulses and the tendency of the crankshaft to want to oscillate. Everybody knows the flywheel does a great job of damping the pulses, but left alone the crankshaft would go sinusoidal in its rotation and destroy the front bearings. Engine designers have, over the years, come up with a number of ways of balancing the front. The two most common ways are to build counterbalances into the crankshaft itself or to add a harmonic balancer at the end."

"Okay, so why is this one bad? It looks fine to me," replied Dabney, looking at his watch.

"That balancer looks like a heavy 'doughnut' of steel, but it's actually two heavy pieces bonded together by a thick layer of synthetic rubber. The idea is that when the engine revs up, the inertial pulses of the inner piece are offset by the flexing of the rubber as the outer piece resists the movement. This works quite well until the rubber becomes cracked, hardened or damaged through age and use. When that happens the engine starts vibrating and the pulley attached to the outer ring of the balancer starts pulsing. That pulsing, my Boy, is what is causing the belt to fly off. It's actually starting and stopping in its rotation, causing the belt to stretch and fail," said the Doctor.

"How long will it take to fix this, Doc?" asked an ever-more-desperate Dabney.

"Well, since we can't rebuild the balancer ourselves we can either find a new one at the local parts store or maybe find a used one at a junk yard," replied the Doctor.

"I'm running out of time, Doc," said Dabney. He thought a moment. "Hey! I have a '67 Buick station wagon back in the other building and I think it's a 350 engine. Would its balancer work on the GS?"

"It's worth a try," said the Doctor.

They quickly walked to the other building, carrying the necessary socket wrench and breaker bar to remove the balancer. It appeared to be the same size, so they removed and installed it on the GS engine. Once the belt was replaced they started the engine, whereupon the belt ran smoothly. There was just enough time to wash up and get to the parade.

While driving the parade route a bystander shouted, "Hey Dabney! How do you keep all those cars running?"

"No problem," Dabney yelled back. "You just have to maintain a calm demeanor and keep a sense of 'balance'," said Dabney as he winked at the Doctor sitting next to him.