Just a Simple Wrench
by Jake &Ann Snyder
This Could Happen to You
We had just finished filling the tank of the ’72 GT, and we were only a half-block from the monthly meeting site, still sitting at the Shell station. Both of us had been considering what we should order because the trick to getting supper at a packed monthly meeting was to decide quickly and, especially, get there early. A problem developed as soon as the key was turned: There was the expected ignition warning lamp and the sound of a busy starting motor, but nothing else. Not a cough, not a backfire, nothing. This is not the sort of thing that happens to a stock MG that is reasonably maintained. In fact, a substantial amount of maintenance had been done in the past few days, no more than a hundred miles previously.
With the promise of an early spring and the threat of a month overdue EPA notice, the tuneup had been started. The right-side motor work (retorquing, setting the valves, cleaning and checking the plugs, and pulling, inspecting and servicing the distributor) had all been taken care of the preceding weekend. (The left-side motor work, which is checking the intake manifold gasket and setting the carburetters, would be done the next weekend). The head nuts had been retorqued - one at a time, in the approved spiral sequence, each nut was loosened while watching the breaking torque just to be sure none were in the 20 foot-pound range. Then the stud, nut and washer were flooded with clean engine oil from an pump can, followed by tightening to as close to 50 foot-pounds as possible. The reason for retorquing the head has to do with the tendency of the gasket to compress (and maybe, the studs to stretch) over the years, resulting in low torque and the possibility that the gasket will loose its grip and leak. So if the head is to be retorqued, clearly this step must come before carefully adjusting the valve lash. Retorquing was repeated ten times for the total of eleven head nuts, quickly, before the engine could cool, and the valves were ready for adjustment. We removed the plugs and turned the engine with a button temporarily connected to the starter relay. This is easier on the battery, and the plugs have to be cleaned anyway (sandblasting with the porcelain insulator protected with masking tape works well). The valves were adjusted to 13 thousandths, the specification for a ’72.
Finally the distributor was removed, a bad vacuum advance replaced with a new one, the centrifugal weights and stub spindle oiled and new points installed. And the rub block on the points was properly lubed with grease. The oxidized brass was scraped from the inner terminals of the cap (the gap between the terminals and rotor did not seem to be excessive), and then the cap and wires were sprayed with Simple Green and washed in warm water. After drying overnight, the resistance of the wires was checked and all were between 5000 and 10000 ohms, with the longer ones having the higher resistance. None of the wires had burned out yet, and would probably last till the next tuneup. The ignition timing was set statically to 8 degrees before top dead center, and then further adjusted to 15 degrees before top dead center at 1500 rpm with the vacuum pipe disconnected and plugged for the adjustment. Everything had gone perfectly, and we commented during the forty-five minute drive to the Shell station that the GT seemed more responsive than usual.
So there we sat at the Shell station, with the promise of an early supper disappearing. Fortunately, there were the usual parts and tools in the GT, and we probed for power in the distributor with a 12 volt test lamp (yes, on the low voltage side) and spark from the coil wire (some, but not fat blue sparks all the time when the points were opened with a screwdriver). We both noted that working on a distributor with current flowing through it somewhat diminishes the comfort of the knurled barrel of an aluminum Mini-maglite, though we did not on this occasion get shocked, which should have been a clue in itself. Anyway, one of us cranked the car again, and it started, and idled just fine. We got in, rehearsing our order to the waitress, only to find that the car had absolutely no power - any attempt to do anything besides idle resulted in a stall. Restarting gave a little burst of engine speed while the tachometer flicked between 1000 and 3000 rpm, and that was the clue. When the tachometer needle jumps all over, there is usually a points problem, generally too small a gap. We popped the distributor cap again, and examined the points. The gap seemed about right (removing the distributor from the engine is the only way to see the points well enough to set them accurately, especially at night). Well, perhaps it was the low tension lead passing too near the spindle. No, the position of the lead could very easily be changed by twisting the terminal on the points post. THAT WAS IT. The nut on the points that held the low tension lead and the condenser lead was very loose. Sometimes there was a complete circuit, sometimes the condenser was not connected, and sometimes the low tension lead was not connected. Sometimes it would run, sometimes not. At least we had gotten to the Shell station. Finding a little socket that fit and a few twists solved the problem. The reason the nut was loose was less clear. Had it not been tightened when the points were replaced? Or had the plastic insulator compressed and permitted the nut to loosen? In either case, we will check the nut in a few hundred miles just to be certain that it stays tight. After all, supper could be riding on that nut again.