I am following this topic already since the beginning. Main reason was that I have done a few improvements (exhaust, Wolf remap, K&N filter), so improving air intake looks like a necessary last step. I opted for using the original airbox and added a tube from airbox to the right hole in the valance, which I enlarged and connected the hose to a trumpet in that hole. I noticed some improvement and slightly colder air measured by the OBDII. After a short holiday to the Harz (Germany) and a fast autobahn drive home I noticed oil on the garage floor. I tried to find out where it came from, but could not find any leaks. I took the Morgan to the local garage, who also could not find any leaks. The mechanic however had an idea what could have caused the oil leak. According to him the pressure build up in the airbox behind the radiator could have been so high that it caused an increase of pressure in the cylinder head through the carter ventilation pipe. I took the air tube from the trumpet and mounted it behind the valance, not directly in front of the car, so no direct pressure. After a weekend trip with the Morgan to the south of Holland (approx 500km) no sign of oil leaks. Does this problem ring any bells to all involved in this topic? What could be a solution or maybe something else causing the oil leak.
Wolf tuned (exhaust+cat+remap) 4/4 1.6 Ti-VCT 2014
For what it is worth: Just back from 2,500 mile run to North California Flog Mog. I installed a 4" hose from top of rad to air filter. Temp stayed at about 200F + or - the whole trip. AIT stayed at about 104 F. I did not notice any improvement in Performance. No change so far as I could tell. I will remove the hose and check the AIT temp to insure the hose is effective.
Button: I tried an experiment today with my 4/4 using silk strips on the radiator grill and observed little air going into the top of the radiator. This would indicate that you might not be getting the airflow you thought you might get through that narrow space. Not very scientific I know but thought I would mention it.
Bruce 1964 4/4 Series V Comp (Megan) 1994 +8 (Maurice) tis no more 2013 M3W (Olga)
Even though this video was shown on TM years ago, here it is again. It is very revealing. From above the radiator through the cowl it is not to expect a lot of airstream. It is a low pressure zone or at least an area where turbulences appear. The same applies more or less to the sides of the bonnet. If dust or wetness are not a problem one should suck in the fresh air from underneath the car or in other words lead it up by the airstream using a pipe/hose. To protect from dust or at least from small stones a filter or a grid could be mounted upstream of such a pipe in the way Bruce did it.
Button your last picture shows a huge round open filter in the other thread. The pipe which leads the air from the front just has a relatively small contact area to the air filter. So I think most of the air which is sucked in the filter will come in from other directions as well where the air is warmer. A solution could perhaps be a filter with a different shape like Bruce‘ filter which is smaller or with a more focused intake area to get the most of a cold air pipe.