1st and 3rd series single six engines

Posted by Richard Sturdy On 2015/2/17 11:39:33

We are about to start rebuilding the engine for my 1922 1st series 126 Touring. I have the original engine and have obtained another 1st series engine and a third series engine. We intend to build a near-perfect engine from these three, plus a spare. However, I understand that the 3rd series had a bigger displacement - 288 ci against 268 ci, I believe. Can members advise whether the extra cubic inches were obtained by means of a larger bore alone, or was the stroke also increased? Obviously, this will affect the interchangability of parts from the 1st and 3rd series engines.
Thanks
Tricky Dickie