Allison V-3420 which was two V-1710s married. Designated as the Allison W engine. This one is out of the
Adios - the boat that use to be on the park pedestal outside Pasco's Columbia park. Loyd Jett it was said had 1 or 2 of these at one time. Back in the early eightys, Tommy D'Eath told me that when Regas drove this Adios boat (Eager Kaiser owned it), that he was small enough to crawl up and into the open hole into the wet sponsons and remove some sort of air-trap plates in order to gain access to the bottom spark plugs. Be it folklore or whatever - that's what TD told me.
JC
Ed. note - check out the size/specs on this mighty motor here -
http://en.wikipedia.org/wiki/Allison_V-3420