The MGA With An Attitude

This actually has more to do with cooling the passengers than the engine.

At 06:11 PM 4/12/05 -0600, Barry Sandman wrote:
>"I have fallen in love with the push rod coupes but it is my understanding that they are bloody hot. I know the Twin Cam engine throws off a lot of heat, but how's the push rod coupe in that department?"

About the same. There's not much difference in thermal efficiency, so the heat output is proportional to the fuel consumption, regardless of engine type. In stock form an MGA traveling on the open road at a steady speed between 45-60 MPH might get about 30 MPG. So at 60 MPH it would use 2 GPH of fuel. Thermal efficiency might be as low as 25%, so 75% of the heat of combustion is expelled as waste heat.

A large part of that heat goes out the tail pipe, some is radiated from the exhaust manifold and pipes, a lesser amount is radiated from the engine block and cylinder head, and the rest (probably less than half of the waste heat) is expelled through the radiator. Heat from the manifold, block, head, and radiator ends up being added to the air in the engine bay. That hot air heats the bulkhead and tunnel and floor as the warm air passes.

Now if I hook up my trailer and beat it down the expressway at 80 MPH the fuel consumption might be more like 20 MPG, and at that speed it would be using 4 GPH of fuel. Doubling the fuel being burned means doubling the heat being expelled. The cooling system is then pushed to the limits as the temperature gauge climbs higher. As long as it's moving at road speed it probably won't boil, and everything is okay, but the tunnel and bulkhead get hotter.

The passenger compartment heats up according to how much heat migrates through the walls. It helps of course to plug any and all holes in the bulkhead so you don't get the hot air traveling directly inside. Put a bright drop light in the engine bay at night and stick your head under the dash to see where the open holes might be found. It also helps to put about 3/8 inch of carpet padding on the tunnel, floor, toe boards, and on the chassis closure panel between the toe boards and the goalpost crossbar.

The Coupe originally had a thin foam insulation pad on the passenger side of the heater shelf and bulkhead, which also happens to work well in the Roadster. Moss Motors sells a replacement pad which has about 1/8" of felt which is faced with about 1/16" of textured soft plastic (synthetic elastomer but not neoprene). This appears to be a good sound deadener, but will likely make a fair thermal barrier as well. You could likely get equal benefit from 3/8" shredded urethane foam carpet padding. This is commonly sold with foil facing on one side, which is often used for under hood (bonnet) sound deadening.

If you do this much insulation the Coupe should be at least bearable in hot weather. One key to survival is to be sure the heater valve is adjusted to shut off all the way so you can get cool air ventilation on your feet through the heater box. Some people actually prefer the Coupe to the Roadster in harsh direct sunlight as the Coupe roof makes for a nice sun shield.

On the other hand, if you will drive the Coupe regularly in hot and humid weather, like around Florida or along the Gulf coast in mid summer, you might consider air conditioning.

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