In the beginning, there was slug. (Slug is my friend Mike Rivers's cream-colored 1981 Mercury Capri.) Slug didn't have much "get up and go". Mike and I would get Slug on the freeway, carpooling together to work in the morning, and Mike would floor the gas, and slug would jump into passing gear, and his engine would make a loud labored noise, but there was no head-snapping burst of acceleration. Not even the slightest twinge in the neck muscles, in fact. Just a slow, steady increase in speed, until third gear engaged about 20 seconds later, at which point the whole car lurched violently, and finally started to accelerate a little. Slug went from 0 to 60 MPH in about 60 seconds! Pathetic.
Also, there was always the stench of exhaust fumes in the passenger compartment. And whenever you'd take the cap off of the oil intake pipe, a steady stream of exhaust smoke would pour out.
Bad piston rings, you say? Mike checked that out, and no, the rings were fine. Carburetion too rich? No, if you made it any leaner, it wouldn't run at all. And yet the smog analysis ($40 worth) said that the car was producing 5 times the allowable amount of carbon monoxide, and was a "Gross Polluter". So what was the problem?
So Mike took the engine apart and noticed that the valve guides were badly worn. So he took the head to a machine shop and had that fixed. The machine shop had to do the job twice, because they messed it up the first time. They also replaced all the freeze plugs, but forgot to use sealant. (That was to have disastrous results in the near future.)
But after the valve-guide repair, the car was no different. The engine still made loud noises, and the car still had no power. So what was the problem?
Timing? Mike spent weeks trying different timing setups. It only worked at all with the timing set about 20-25 degrees before TDC. (Factory specs said set it at 10, but it had no power if you did that.) So it wasn't a timing problem. And yet the car ran pretty good at low rpm, about 1000-2000rpm. But at 3000rpm, the engine would make a loud, labored grinding noise, and yet it had no power.
Spark advance? No, both the mechanical and vacuum advance systems were working perfectly.
And then Slug started overheating. He boiled over on the freeway when Mike was coming back from a long-distance trip on Saturday, August 22, 1998. At first Mike thought is was a cooling problem, but no, the entire cooling system checked out ok. Water pump, radiator, hoses, thermostat, coolant, all were within specs. So why was it overheating? The mechanic at the service station Mike pulled into when it boiled over asked Mike about the symptoms the car had been having. Mike described all the crazy shit Slug had been doing lately. The mechanic said, "sounds like a bad catalytic converter, to me." Mike thought, "what does the catalytic converter have to do with anything? It just changes carbon monoxide into carbon dioxide. What does that have to do with power loss or overheating?"
And then, on Monday, August 24, 1998, while motoring down the freeway on the way to work in the morning, we noticed a huge plume of steam or smoke gushing out of the rear of the car. Then it started coming up through the cut-out around the emergency brake, and up through the vent in front of the windshield. And the temp gauge started to climb. So we had to pull Slug off the freeway and ditch him into the parking lot of Fry's Electronics in Fountain Valley. The temp gauge was just going beyond "H" and into uncharted territory as Mike shut the engine off. After we let Slug cool down for a while, I fetched a pail of water, and Mike poured it into the radiator, but it all poured out of a gaping hole in the side of the engine block. One of the smaller freeze plugs had popped out, and all the coolant had spewed all over the engine, creating the giant plume of steam we had seen.
I noticed that the exhaust manifold was extremely hot, much hotter than could be accounted for by twenty minutes of freeway driving. I also noticed that the freeze plug which popped out was the one closest to the exhaust manifold. On a whim, I asked Mike, "Could there be something occluding the exhaust? That would explain the overheating... and the blown freeze plug... and the loss of power... and the labored sound of the engine... and the fact that the car performs better at low rpm than at high... " Mike said, "Well... maybe the catalytic converter is clogged."
So Mike called a tow truck, and towed Slug back home, and I had to take the bus the rest of the way to work. Bummer.
All that day, Mike worked on Slug. He took the primary catalytic converter off of the engine. (As I understand it, it mounts directly on the exhaust manifold, and is in-line with the exhaust pipe.) The inside of the primary catalytic converter was one solid block of charred, melted muck! Very little of the exhaust gases were getting through. Most of the exhaust had been forced past the piston rings, through the crank case, and out the oil intake pipe. No wonder we had been smelling exhaust in the interior! No wonder Slug was having severe problems! Also, the secondary catalytic converter, further down the exhaust line, was empty. Just a hollow pipe. No wonder Slug was spewing 5 times the allowable amount of carbon monoxide!
So Mike replaced both of Slug's catalytic converters, and all of the freeze plugs. (He used sealant, unlike the machine shop which had refurbished the head.) Afterwards, Slug was a new car. His engine purrs now, instead of wheezing and grinding. And when Mike steps on the gas, he accelerates vivaciously, enough to snap your head back, instead of just oozing along like a half-dead slug. He's not just "Slug" anymore... he's "Slug On A Hot Tin Roof"!