JIMNLIN wrote:
Our older trucks didn't have the front under the bumper air dam. Engineers found air flow under the engine bay wouldn't let hot air escape fast enough and was creating hot running engines when pulling a heavy trailer (example).
The air dam helps create low pressures under the engine bay which allows more air flow through the radiator ...over the engine and on out the bottom.
This was happening when I was towing for a living. Sooo... we made air dams for our older trucks or bought them from a dealer if our trucks had the same bumpers. Worked great on my 454 GM trucks. No more fried spark plug wires and no more hot starter motor/no crank issues.
Never noticed any mpg changes in that type of work. Just a steady 4-6 mpg on those old carbureted BB engines.
Newer trucks ?? Truck MFG engineers can give us the skinny on their use today.
Back in the day, we would put spacers between hinge and hood, to get a gap about half inch. That let a lot of heat get away from that 427, drop the temp much quicker after top the hill. Going up hill, grossing 110,000 was hard to hold enough speed for airflow.