why does the engine need tins? why not go without?
 

I've never had a good answer to why we need tins on these engines. other than keeping road junk and dirt out of the engine compartment what purpose do they really serve? I've heard vague references to cooling and differences in air pressure but nothing concrete. any thoughts?

I have always been told the tins for air cooled motors are to ensure that the heated air blown down do not get sucked back into the cooling air intake.

My understanding is they keep the hot part of the engine separated from the "cool' part. This facilitates better cooling along with keeping the hot air away from the air intake to the engine. Not a mechanic but that is how I've heard it expalined.

thanks guys.

that makes sense. a hot air zone below and a cool air zone above.

that's what I always assumed was the reason but I was wondering if there was more to it than that. I guess not.

Don, the engine fan creates a low pressure zone on the upper area, and a high pressure area under the engine. If there was no tin, there would be very little airflow through the engine lid grille, and the fan would suck hot air from below the engine. Rapid overheating would ensue. Even the rubber gaskets on the lid and closure panel are important to ensure cooling air is drawn through the grille.

Prevents fuel vapor lock on a hot day with HOT exhaust manifold.......