MGA! Tech Talk – September/October 2018

Thank you to all who participated in GT-43! Having so many NAMGAR members with beautiful MGAs in Richmond was a real treat. During the Awards Banquet, I took note of how many people were recognized for driving their cars long distances to attend. This is a real testament to owners who maintain these cars so that they may travel such long distances without breakdowns.

I did find it disconcerting that some of the owners who drove their cars talked about being plagued with high engine temperatures. After a heated debate, the conclusion was usually, “If it isn’t boiling, you’re okay.” “Cooler is better,” might seem like a better answer, but that’s not necessarily the best advice for our MGs either. So, what is the optimum operating temperature of the B series engine as fitted to the MGA & Magnette? And how do we go about getting our cars to run at that temperature?

There are several aspects that determine what optimum engine temperature should be, and a very long list of factors that lead to the engine meeting that goal.

Oil temperature is also an important aspect, maybe even more so than water temperature. Because oil heats and cools during drive cycles, condensation will form inside the crankcase. And the only way to expel that moisture is to either change the oil very frequently or heat the oil hot enough and long enough to burn the water off. This gets us thinking that oil needs to be a minimum of 212 degrees Fahrenheit. But there is more to consider. Think, after a summer rainstorm. Once the sun comes out you see steam and soon the ground is dry. This isn’t from it being 212 degrees and boiling the water (well, maybe it does in Phoenix). What is really happening is evaporation. And so, this can happen inside of your engine, provided it is run long enough to accomplish that task. Multi-grade oil has a specific temperature range to achieve a desired viscosity. This usually starts at around 200 degrees. Viscosity can begin to fall off above 260 degrees. Above 300, conventional motor oil can no longer protect your engine.

The oil in the pan will generally run a few degrees warmer than your indicated water temperature. But circulating oil, such as the underside of the piston and cylinder wall, can reach peaks of up to 50 degrees higher. When all the factors are considered, oil temperature should be about 210 degrees under normal running circumstances.

Then there’s gasoline. Some even remember older cars vapor locking back in the day. As gasoline quality improved, this wasn’t a problem for many years. But since the introduction of ethanol gas, vapor lock conditions have returned.

Vapor lock is a condition in which the gasoline changes from a liquid to a vapor while still in the delivery system. Modern ethanol pump-grade gas will begin to evaporate in your tank at only 100 degrees Fahrenheit! And it can be even worse at higher altitude and worse again if using a winter blend. Many North American filling stations switch to a winter blend in the fall for easier starting of automobiles throughout the winter. As many of us fill up our cars late in the fall and store them till spring, the result is we suffer through the first 300 miles of a new driving season with gas that has already begun to varnish from time and starts to boil at an even lower temperature!

Pressurization of gasoline in the line from the electric fuel pump will help reduce the occurrence of a vapor lock on a hot day. But once the fuel is delivered into the carburetor bowls, it is back to atmospheric pressure and will immediately begin evaporating and actually start boiling around 170 degrees! Lest we forget that the carb float bowls sit in proximity of the exhaust manifold too! So, here’s a big reason to keep engine temperatures to a reasonable level, and especially overall under hood temperatures.

Weighing in on all the aspects, it is my humble opinion that an MGA will do its best to serve you in any conditions and will run right along at the peak of temperature conditions. But to give your car a well-deserved chance, aim for an operating temperature on your water gauge of 180-200 degrees Fahrenheit (82-94 Celsius) and an oil temperature of 210-230. Meeting these attributes will go a long way to contributing to the drivability and longevity of your engine.

In the upcoming issue of MGA! we will delve into how to best achieve these results. While adding an electric fan to cool the water temperature, or a cooler to reduce oil temperature may certainly add benefit, these changes can and do affect the engine overall. We will examine each of these “Fluid Systems” and how to dial our cars in for better efficiency and longer life.

I welcome your feedback and any research you have already done regarding this “hot topic.”

Meanwhile … Stay cool!