I finally decided to fit the Air Shield that I purchased from Ed Melberg.
(This post is pretty-much a cut & paste from the forum that I am a regular on..)
The shield is shown here in the C60 (air/con) chapter of the Assembly Manual with all the dimensions for the mounting bolt holes. Lots of detail..
Both they and the shield are accurate and the shield fitted easily.
For drilling the front side of the radiator support, I had very little room for getting in a drill between the valance, let alone one with a drill bit in the chuck. So, I put a center-drill in my die grinder and it fitted and drilled easily.
These bolts from AMK (B-10415) are not THE correct bolts as the correct ones aren't available anymore, but they are very close and have the same self tapping flute in the thread like the correct ones. (-just like the 68-69 fuel and brake line clip bolts do.) They cut their own threads really well and just by using a ratcheting ring spanner to tap and install.
Done. Very neat and OE!
(..and no, I didn't need to cut an access hole in it for the remote oil filter like I thought I was going to. Phew!)
The whole idea of the shield is to maintain a low pressure area behind the radiator when the vehicle is at speed. This encourages the most amount of air to pass through the radiator and not allow air from under the valance that has "cheated" the radiator to fill the low pressure void.
Now. all I need is a hot day to see if it makes a difference.. The other day (without the shield) was a humid ~30°C (86°F), and the engine was cruising (@3500) with the temp at 190°-200°F with the A/C on high..
With OE thermostats being 195°F, that temp is hardly a concern, but I have a 170°F 'stat fitted at the moment and would like a little reserve up my sleeve for stinking hot days.
Otherwise, it rarely makes it to 180°F on cooler days with the A/C off, so the system works well.
Switching on the A/C typically adds 10°F.