I installed plain steel valve covers and the paper element converted aircleaner back on the 351 that is still in my 55 and noticed a drop in gas mileage on a short trip last weekend,I had it on when I first go it on the road but was removed for a open element aircleaner when I started driving it to Florida. last might I cut the bottom off at the seam and welded the lid to what is left and made it a top for a open element aircleaner so it will breath a little better,I also cut the baffle out so I am going to take it for a drive this coming weekend to see if the fuel consumption goes back the where it was. Years ago when I had a 53 Olds I installed the 53 oil bath aircleaner on the slightly newer 59 motor and the gas mileage dropped a bunch so all I did with it was used the top on a open element aircleaner and the mileage came back and had a nice sound when the secondairies were opened. I will post some pics of the modifications and it still looks somewhat original but not as tall and will go on the 292.

Butchering up everything I can get my hands on in Dayton Ohio