All MG drivers know how easily a car starts in July-why you do not even need to touch the choke! Just turn the key with the gearbox in neutral and the engine catches, often on the first cylinder that fires. As the weather turns colder there are more starting issues, even with top-notch battery and ignition connections and components. Certainly the choke is necessary in cold weather as the fuel, even winter-blend, does not vaporize as completely and so much more of it is sprayed into to air stream by the choking mechanism.
Besides being necessary for starting, the choked condition must be maintained until the engine will run under load without backfiring. This is especially important for our supercharged engine, where a backfire would supply an already compressed charge for the supercharger to compress again. We do not know how long the rod bearings would last if the compression ratio reached 15:1 or 20:1, and we are not prepared to put too much trust in the poppet valve on the supercharger that “protects the engine from backfires as best it can”. Thus, after the engine starts on choke, it must be run on choke until warm enough so that backfiring is unlikely.
So there is enough fuel vaporized in the air for the cold engine to start and run, but what happens to the rest? Some of the extra fuel never burns completely and is expelled from the exhaust on a choked engine. This is why it is a good rule of thumb is never to start a cold engine within a car’s length of a white garage door-the resulting patch of soot will take a lot of extra painting effort to eliminate. But a lot of the extra fuel on a choked engine winds up in the oil as it washes down the sides of the cylinders, removing the lubrication that is essential to minimize piston ring wear and maintain compression.
We check the dipstick for a fuel smell at least once a week in the winter. When we smell gasoline, it is time to change the oil, even if the temperature in our unheated garage is no higher than zero degrees Fahrenheit. This is no fun at all, but it is necessary because running an engine with oil diluted with fuel guarantees extra wear and early failure of internal parts.

The kit includes an instruction sheet, the core plug heater and a power cord. The extra core plug domed disk is shown for comparison and is not included in the kit.

There is an alternative: heat the engine before trying to start it. Types of heaters include (1) a drop cord with a 100 watt lamp (make certain the guard is metal and not plastic), (2) a dipstick heater that is placed into the oil dipstick hole, (3) a magnetic heater that attaches to the oil pan, albeit insecurely, and probably several other variants that are available from W&Co, all of them working to a greater or less degree and all having inherent drawbacks. We have tried them all, and there are only two that are worth the trouble to set up and plug and unplug every day. One is the drop cord, though this really only heats the carburetter, which means the engine will start even if the oil is not circulating too well, and the core plug heater, which is what the OEM auto manufacturers use as well as those who winterize vehicles for extremely cold service: in fact, we bought our first core plug heater at a very small Western Auto parts store in Seward, Alaska more than a decade ago.
The heater costs about $20 and is also available by mail order from PartsAmerica.com as part number 11603 (heater freeze plug) in the event that Seward, Alaska is not on a foreseeable itinerary. The heater must be for a 1.625 inch (40 mm) core plug hole. Spare cords are available separately from napaonline.com. One cord, which is longer than the original and has a heat-proof shield so it can be left attached to the core plug heater all winter, is Engine Heater Power Cord Product Number: BK 6051511 for about $15.
The basic installation is simple: drain the coolant, remove a core plug (“freeze plug” to some) and replace with a core plug heater. There are a few specific hints that help:
(1) Drain and save the coolant in a secure place (coolant is attractive and poisonous to animals and children).
(2) Remove the oil filter and distributor. Wrap the filter head with plastic and plug the distributor hole.
(3) Bore a one-eighth inch hole in the center core plug. Remove the core plug (a seal puller with curved ‘horns’ works well).
(4) The heater cannot be installed according to the instructions that comes with the unit because there is a flange on which the core plug seats and the heater is made to fit into a 1.625 inch smooth bore. Instead, use a thin 1.625 inch O-ring seated between the bottom of the core plug heater and the core plug flange. The heater attaches with a molly-bolt fitting. Feel around the inside of the block (watch for sharp casting flash!) to determine how to point the heater element, which is somewhat larger than the bore. Ours seems best with the loop of the heater pointed toward the front of the engine. Use only silicone grease to lubricate the O-ring. Gently tighten the molly-bolt. Try not to squash the O-ring to the point where it is cut into pieces which will not seal as well. Replace the oil filter, distributor and coolant. Do not plug in the heater without coolant-it will burn out immediately.
(5) The available heaters are in the 400 watt to 600 watt range. Connect with a timer to turn on two hours before the engine is to be started. There will be a “sizzling” sound as coolant around the heating element boils when the heater is on. The whole block should heat to 100 to 120 degrees Fahrenheit within two hours and the engine will start immediately if all else is in order.
So far, we have had leak-free service from this unit. With the power cord removed and stowed, a person would need to know where to look for to find the core plug heater, especially since it is hidden behind the oil filter. Besides starting almost immediately, the engine reaches a temperature that does not require the choke after running for a minute or two, compared to ten minutes or more of choke-on time on zero degree days. This cuts down oil change intervals to that performed in the summer. And there is immediate warmth from the defogger and cabin heater, a very remarkable situation that we used to doubt was possible at all.