|The MGA With An Attitude
COLD WEATHER STARTING for the MGA -- CB-103
One prime ingredient to easy starting in cold weather is good compression. If your engine has low compression, like below 110 psi, expect it to start on fewer than four cylinders and have to run for a few seconds before it willl run on all four. This is partly because liquid fuel does not vaporize well when it's cold, and low cylinder pressure makes it a little difficult to ignite the fuel/air mixture. But more important, low cylinder pressure makes it much more difficult for the engine to muster up enough power on the first few strokes to keep on turning over through the next compression stroke.
When compression is 125 psi or better it should start okay in cold weather. If one cylinder is below 110 psi it will be hard to start when below 40 degrees, and may not start at all when below 10 degrees. When two cylinders are below 110 psi it will be slow starting in mildly cool weather, difficult starting below 40 degrees, and may not want to start at all at 20 degrees. This is because it would be starting on only two cylinders, and the combination of low torque and high drag at cold temperatures may not give it enough torque to stay running on only two cylinders. This is when a little feathering of the throttle might make the difference to get it off of stumble and into fast idle before it coughs and dies. If you can get a few hundred RPM with your toe down just a tad it should keep running, and running will improve dramatically during the first 10 seconds of continuous running.
If you leave the car outside, when temperature drops below zero all bets are off. When temps are below zero you might consider getting out to start it once in the middle of the night. It's a PITA, but maybe better than needing a jump start in the morning. If you can get it to start consistently in sub zero temperatures, you'd be doing better than most, but at least in theory it should be possible. Key ingredients are a good battery, good tune, and all ignition and carburetor parts in good condition and properly adjusted. A 40,000 volt Lucas Sport Coil will help cold weather starting, and is highly recommended if you intend to leave the car sit out in cold weather. If you garage the car at home, then you might be concerned about parking it outside at work during the day in very cold weather, and maybe not starting when it's time to go home. In that case, maybe start it up once for 10 minutes during lunch hour.
Use proper viscosity engine oil in cold weather. 20W50 is bad news in sub freezing temperatures. If it starts at all at 20dF you could expect only 20 psi oil pressure until the oil warms up. Below 40dF starting temperatures, use no higher than 10W40. Consistently below 30dF use 10W30. For starting temperatures near 0dF, maybe use 5W30 oil, but change to thicker oil when the daily temps climb regularly above 30 degrees. Do NOT run 5W30 oil in the MG in warm weather. One other thing. If you have to be able to always start with no assistance in sub zero weather, it might be a good idea to carry one of those small jumper battery packs, and be sure it's always changed up. Carry jumper cables, and maybe a can of starting fluid too, just in case.
Do not run around all winter with half a tank of fuel or less. If the car is not driven a lot of miles, keep the fuel tank near full to minimize condensation in the tank. Large air space and big temperature swings promote condensation. If you run through at least a full tank of fuel each week, then it will likely be okay to run the tank near empty before filling to full. When you use that much fuel, any condensation will be consistently flushed out and burned with the fuel, and you shouldn't have any of those problems. Then it's actually better to run below 1/4 tank before refilling. Consistently refilling before going below 1/2 tank can lead to accumulation of condensate water in the fuel, as it does not get flushed out with each tank burned.
When in doubt in sloppy winter conditions, put a bottle of "Heat" or other CHEAP gas line dryer in with every second tank of fuel. Fuel treatment like STP engine cleaner does nothing to combat condensation. You need the stuff with high alcohol content to absorb moisture and keep it in suspension. These are commonly called "fuel dryers" and may contain methonol or ethonol (same stuff used for 10% content in gasohol fuel).
One serious concern is possibly getting a bad tank of gas with water in it which can lead to a frozen fuel line. If you want to cover your tail for that case, carry bottle of "gas line antifreeze". This stuff will contain isopropol alcohol, same as rubbing alcohol, and in fact a bottle of rubbing alchol will do just as well. One small bottle for 10 gallons of fuel is enough, and you keep it in the trunk and never use it until the day you might actually have a frozen fuel line. Then you pour it in and shake the car to mix it with the fuel, then switch on the key and wait for the fuel pump to do its thing. If you have even a tiny trickle of fuel through the line, this stuff will litterally disolve the ice as it passes and clear the ice in a matter minutes.
And last but not least, be sure your battery(s) is/are in good condition and all the heavy cable connections are clean and tight for lowest resistance and best cranking current. This shouldn't require much encouragement, because it will quickly become painfully obvious if you neglect it.
Enjoy your winter driving, and I hope this helps a little.