It was highlighted in yellow in the guide on 1/4/2013, as of today, 1/8/2013, it is not in the guide. I have a copy of the guide from 1/4/2013 when I downloaded the excel file that shows it. When I checked it today, it isn't there.

It was there and now, poof, its gone.

It was in the NHRA Engine Blueprint Specifications on 1/4 and is still there today, 1/8, as a cylinder head casting.

E = 2780559,2780559-M, 559-M1, 2531110M2 alum

Anyone know what a 559-M1 head is? That was added since 1/4, which previously only listed the 2531110M2 alum. Is there another source for steel head castings?