472 Engines

[WhiteCaddy70]

From what I can find, the 68-69 472 engines were 10.5/ 1 compression ratio. The 70 472 engine is 10/ 1 compression ratio. Why did Cadillac make this change in 1970. Thanks.

[Dave Shepherd]

Maybe the onslaught of upcoming emissions, look at what happened in 71,  Or they saw that .5 made no difference in power, yet put high test fuel on the edge with 10.5.

[TJ Hopland]

The change was in the chamber shape and size in the top of the piston.  By that time they were dealing with emissions regulations so maybe the change gave them a slightly better swirl or flame propagation that helped emissions?  Could also be related to the 500 that came out that year.  Maybe during testing for the 500 they found some advantage that they also applied to the 472.  Pistons and crank were the only difference between the 472 and 500.  The first 4 years the 500's had different oil pans but that was due to it only being in the Eldo's.   

["Cadillac Kid" Greg Surfas 15364]

My recollection of my conversation with Mr. Robert Templin who was Chief Engineer of Cadillac Engineering during the time these motors were developed is that it was a combination of just correcting the actual numbers (in static compression ratio), and making the engine perform better.
They knew back in the early '60s that emmissions were coming and compression ratios would be dropping drastically, but that was already scheduled for the '71 models across the GM lines.
Greg Surfas