Thought I'd make a seperate post for this so it can be easily googled.
http://www.classiccar.com/forum/discussion/142291/head-tag-info/p1
http://www.classiccar.com/forum/discussion/140378/engine-id/p1

Just received this from Roy Marks, concerning the aluminum tag that is on the head of a 1951 308 that I saved from the scrap yard.

I called Gus Souza in Illinois who has raced and rebuilt Hudsons for nearly 60 years. He says the head is simply a more milled one for higher compression that was an option. According to him there was the standard head, then the aluminum which was a little higher, and finally the head with the tag. He said they will all run on regular gas today, as the gas is made for modern cars that are all high compression.
Roy

Marconi March 2011 Flag
Posts: 549Platinum Member
We've got a couple of these heads at the Twin-H-Ranch and I was wondering about them too. I asked Gary Klann about them and his answer was that because of the aluminum shortages at the time Hudson made some 7.2 to 1 heads by milling the stock 6.7 head. Makes sense to me.
Ken U-Tx March 2011 Flag
Posts: 798Platinum Member
I have one of the later versions of those heads, but instead of a tag, the "Use Premium Fuel" is cast in raised letters on the head. It is on my '53 Hornet Coupe. It runs better on this head than it did on the shaved 262 it had previously, for sure! The aluminum shortage was due to the Korean war. Likewise for chrome, copper and nickle, thus the more extensive use of stainless '52-54, and poorer quality chrome plating on the 52-53's.