Re: The Second Packard "Twin Six"

Posted by JWL On 2008/9/17 11:19:27

Packard53, to try and answer your initial inquiry. I'm not a V-12 expert, but much has been written about the later twelve cylinder engines and the cars they powered. The second generation (1932-1939) V-12s had a unique and interesting valve design. The camshaft and roller tappet/lifter design had the valves sitting relatively high between cylinder banks. The valves intersected the cylinders at an angle that resulted in them being more perpendicular to the cylinders rather than parallel as is typical with a valve-in-block (L-head) design. This coupled with a pent roof piston and flat cylinder head (I believe) resulted in a combustion formed formed by the piston, valves, and a relief in the block and not by a formed chamber in the cylinder head. This design provided for fully machine finished combustion chambers. As far as I know there was no forced induction with these engines. All of this is from my recall, and I may be mistaken in some parts of this description. I also believe that the Auburn V-12 had a unique, but different valve design where the valves were not horizontal with the cylinders. There are many V-12 experts on this site that can quickly correct what I have said.