I bought mine in 1956, still have it, last ran it on the Salt in 2013, ran 167 in our Club Lakester, on my 162 record. e-mail me at
[email protected] and I'll send you the chapter in my book that covers mine. The picture above by Jason shows the original combustion chamber, mine was modified a few times. They are very heavy, thick on the bottom, thin on top. HP depends on many other things, I estimate my Bonneville engine at about 225 or so? Cook made 104 iron heads and one aluminum. Steve Serr of Miller Hi-Speed is currently developing a head based on the original design but much improved.