70 vs. 71 compression

Ok, stupid question, but I've checked the other threads and didn't find an answer:

Just how did Buick lower the compression on the 1971 455? Was it just through the bigger cc heads or did they also change pistons?

Reason I ask is that I've got a 70 455 block (replacement and I don't have the casting number yet), but it definitely has the 71 heads.

 

They dished the pistons a greater amount in 71, i don't know the dish cc's offhand. Randy

 

That's what I suspected. Thanks.

 

Pete, what part of Aurora are you from? Just asking because I grew up there..

Thanks

 

Rick:

I'm in the "new" area out by Parker. Just off E470 and Smokey Hill area. Growing like mad out by here. New mega-mall going in right near here.

Pete

 

Different pistons for '71. '72 was the air pump, but I think the chamber was still the same. I think they started messing with the heads in '73. By '76 they were worth more melted down.