On 9/10/2012, Jim Werner in Syracuse, NY, wrote:
"I was at Watkin's Glen International over the weekend for their Vintage Grand Prix. When looking at the MGA race cars, one of them had a hood (bonnet) with five rows of small vents. I have seen the hood before, and was curious to know more about it. Do you know where these came from"?

Common enough. The answer is, that louvered bonnet came from the same place as all others. It was hand tooled for a single car. As far as I know there was never any commercial source for a ready made louvered bonnet for MGA.

The technique is to uncurl the crimped edge all around to release the aluminum skin from the steel skeleton. Stamp the louver type and pattern of your choice. Then crimp the assembly back together. At several stages of uncurling and recrimping the metal needs to be annealed to prevent cold working and cracking. The louvers will make the bonnet very difficult to paint.

Note that these louvers likely work okay with a cut down competition windscreen. The standard windscreen builds up a pressure cushion in front at road speed, far enough forward to make air flow into the cowl vents rather then out. It is a good idea to keep the louvers forward of the windscreen about 1-1/2 times the height of the windscreen. Design at right may be practically useless with a standard windscreen at road speed, but might help reduce coolant temperature at very low road speed or when standing still. Also for a street cruising car, it may be a bit uncomfortable to have hot air from the engine bay flowing over top of the windscreen during hot weather conditions.

For the pictures below, do not ask why. Just someone's idea of a personal touch.