Is the compression differences between years because of head gaskets and can I change them to achieve a higher compression ratio without hitting the valves on the pistons? I currently have a 1972 455 with 8.5? Thanks, Ron

This comes from a very reliable source...

The difference in Compression Ratio is in the Piston dish and head. You can change the ratio a small amount by changing the gasket to thicker or thinner, but if you want a significant change, you would need to change the heads. The 71 and 72 are Identical, but they just changed the way they rated Horsepower and tourque in 72

Hope this helps.

Jim.

Do you think a 70 head would get me to 10;1? How much does the dished piston affect the ratio? Can I mill the 70 head a small amount without problems? What is the best way to get the most power from my 72 motor(read easiest)? Thank you for any advice, Ron

Originally posted by Ron:
Do you think a 70 head would get me to 10;1? How much does the dished piston affect the ratio? Can I mill the 70 head a small amount without problems? What is the best way to get the most power from my 72 motor(read easiest)? Thank you for any advice, Ron Ron,

A 70 head would give you about 5 less CCs in the combustion chamber (65 CCs vs 71 CCs), and bring you up to about 9 to 1 compression. You can mill virgin 72 heads .030" safely. This would bring the 72 chamber size to that of the 70 heads.

The 70 used a steel shim gasket that was .015" thick vs a .040" composite gasket in 72. You can only use the steel shim gasket on round cooling port heads and round cooling port blocks. Your 72 may still have the round ports depending on the point in the year when it was made. That would give you another .5 of compression and put you around 9.5 to 1 with the milled 72 heads. You may need a shorter pushrod this way, and also may need the heads milled on the intake side for the intake to fit correctly.

Cam selection will depend on RPM range, intake, exhaust, head flow, compression, transmission, rear gear, weight and converter stall. The engine described above is limited by the stock rocker strength and stock piston to valve clearance. A low .500 lift cam is possible with stock rockers. Long duration cams tends to bleed compression and push the power range higher in RPM. A 230* or 240* duration at .050" lift would be in range for your compression and the RPM range you suggested. The Edelbrock dual plane B4B intake is now being manufactured again and works nicely from idle to 5500 rpm. Tell the cam maker or Buick provider your proposed combination and they will design a cam to work with your combination in your car.