4 2 1 just seems to me like an odd number to settle on for a Displacement. We all know of many instances when engines were named one thing and actually displaced something else.

Anyone have any information the the 421 moniker? Maybe its the truth, seems unlikely in this era though.

It does make a cool fender flash however. 

Wait a minute, Pontiac is notorious for faking displacements.

The 326 was actually 336 which exceeded Corporate 330 rule so they just fudged that one on paper.

Since 1964 GTOs always had a 6.5 litre emblem through to 68. The engine was never 6.5 litres. Early engines were 6.4 and later engines were 6.6.

1973 Grand Ams also had 6.5 litre when engine was 6.6 as well as 7.4 when the engine was really 7.5.

When Pontiac shipped the engines down te street to the GMC plant they morphed on the way from 287 to 288 and from 317 to 316.