Figure 1b – Vented Deck-lid Pantera in UK
Jeff wrote: “I did have the opportunity to be following a friends Pantera who was at 70 or 80 MPH when an air conditioning hose let go and filled the engine compartment with Freon mist (looked like smoke!). I can tell you from that experience that the deck lid opening is very efficient at moving large quantities of air from the engine compartment rapidly and smoothly.”
Bob wrote: “Several years ago I cut a piece of Plexiglas slightly smaller than the rear opening and used thick soft insulating material (from JC Whitney) around the outer edge. I have two small Plexiglas handles glued to the rear facing side. I install it when I'm washing the car (the engine compartment is finished in body color and everything is polished) (see Pantera Profiles 99 #2) to keep water from entering the engine compartment. However, I've never tried driving with it in place, but maybe I should.”
Jerry wrote: “Last summer I drove one of my cars to a summer 'do' in southern Kansas. On the way back I ran into a torrential rain storm for the last 5 miles to the house. The car didn't have the rear trunk insert in place and when I got the car in the garage I had a heavy patch of road grime on the rear deck trailing out of the engine compartment. It ran in a wide stripe to the back of the rear deck. It was also heavy enough that I used foaming soap and a power washer to remove it. I was running about 70 most of the way to keep the windshield clear.”
Garth Wrote: “I've thought about installing a belly pan under the engine to reduce the suction of dirt, dust, rocks, gravel, and water off the road and hopefully keep the rear deck-lid a bit cleaner. Not concerned with hot air from under the car helping to cool the engine that's a function handled by the radiator. Now if it were an air cooled engine with cooling fins it would be a different story.”
Bud wrote: “I get dirt on the deck lid to about 12" to18" from opening, seems like more if no trunk tub installed.”
Jim wrote: “The side windows on a Pantera will not allow air to come into the engine bay at any speed above a crawl. There is more air pressure and surface area coming from the bottom of the car than what the window openings have. This was proven many years ago by a good friend of mine in Indiana. He put is Pantera behind his twin engine airplane and used a smoke stick to show the air flow. The smoke would go through the radiator, under the car and out both side windows and the main rear deck opening. I have overcome that problem by using a sealed air box and ducting the air from the side scoops into it. My actual engine bay temperatures are hot, but the air entering the engine is just above ambient temperature. I know that by disconnecting the air box hoses, my engine inlet air temperature goes up 40 degrees.”
You’ve just got to love the Forum – so much accumulated know-how and wisdom!
So, originally there was meant to be a window, but cooling problems got in the way, resulting in a lot of air flowing through the opening and lots of stuff on the engine and deck-lid.
First question – how quickly will the engine compartment heat up if the opening is blocked off and the car is not moving? On a 70 degree F day I blocked the opening and let the car idle while I monitored the engine compartment air temperature, as measured by the inlet air temperature via the remote for my MSD fuel injection. With a hot engine I saw the inlet air temperature go up at a rate of roughly a degree Fahrenheit every 2 seconds. I quit the experiment when the inlet air temperature hit 150 F. As an aside, I had previously noted when I was stuck in traffic on a hot day that the FI would get finicky if I sat long enough. I figured the issue was excess temperatures even with the opening behind the engine open.
Clearly it will get right hot in the engine compartment if one blocks off the opening.
Whilst getting ahead of myself, I have confirmed Jim’s observation that, without a window in the opening, the air in the engine compartment is roughly 40 degrees warmer than ambient. Interestingly, at speeds above 10 or 15 mph, even with a window, the engine compartment is roughly 40 degrees warmer than ambient.
So, in terms of heating issues, it seems likely that the airflow under the car that enters the engine compartment is pre-heated by the radiator and results in an engine-compartment temperature that is roughly 40 F above ambient when moving. When stopped or moving slowly – the heat from the headers and other engine components will quickly heat up the compartment.
A clay mock-up of the Pantera shows that there was consideration given to adding louvers or gills to the deck-lid – most likely to aid in cooling the engine compartment.