340 compression ratio

Steve, Short answer to your first question is YES! However, Al gave the "32 molar suck" when I suggested it. Here's the long answer and a picture of Al's graduated cc beaker-sorry it's sideways! He uses transmission oil and measures the volume of the compression chamber with the head off. The beaker is called a "cylinder head cc kit" and is $200. It comes with a plexiglass plate to put across the chamber. Precision Measurement Supply in San Antonio, TX sells them. www.precisionmeasure.com 7050 Snowflake Drive, San Antonio, TX 78238. 210 684-6472.

Al also loaned me his "Auto Math Handbook" by John Lawlor. On page 9 it has a cool picture of a Duster at the drag strip to kick off the chapter on Compression Ratio. To summarize: Compression ratio = (cylinder + chamber volume) divided by chamber volume. If you find your bore and stroke you can find the cylinder volume by the formula Cylinder Volume=pi/4 x bore(squared) x stroke. As combustion chamber volume is usually measured in cubic centimeters (cc's), you'll want to convert your inches by multiplying by 2.54 to convert to centimeters. Thus 4.04 becomes 10.2616 and 3.31 becomes 8.4074. Plugging the nuns into the formula gives .7853982 x 10.2616 (sqd) x 8.4074….which comes to 695.315 cc's. Now comes the hard part…measuring chamber volume or clearance compression volume…you need to measure it physically. Use light oil, cleaning solvent or even water. You can do this with the engine assembled, but the engine should be tilted so the spark plug hole in the cylinder to be measured is vertical. With the piston at TDC, the valves closed and the spark plug removed, pour liquid from the burette through the plug hole until it reaches the beginning of the plug threads. The amount poured from the burette will indicate the combustion chamber volume.
With the engine disassembled it is more difficult to measure combustion chamber volume. First, you have to cc the head. Then you have to calculate the added volume the head gasket provides. If the engine had flat-topped pistons that, at TDC, were perfectly even with the deck, or top of the block, that's all you'd need. However, that isn't true of many engines. At TDC, the piston may stop short of the deck height. In addition, if the piston top is dished, or concave, it will increase volume…if it's domed or convex, it will decrease the volume of the combustion chamber. In HPBrooks "How to Hot Rod Small-Block Mopar Engines", Larry Shepard of Chrysler's Mopar Performance offers a technique for ccing the block he calls the 1/2 inch downfall method. The head is removed and the engine is positioned so that the cylinder to be measured is vertical. Them the piston is lowered 1/2 inch or 1.27 centimeters from top dead center. The distance is arbitrary. The point is simply to be sure that the entire piston including the dome, is below the deck and fully within the block. Find the volume above the piston and by using the formula for cylinder volume, you can find what the volume would be if the piston were flat-topped. The difference between the figures tells you how much a dished piston increases the overall combustion chamber volume or how much a domed piston decreases it. {Above info was taken from John Lawlor's book}

Seems to me it might be best for you to pull your heads and see what you've got. Easy to measure bore and stroke then! Compute your volume's remembering to take into account the compressed head gasket volume and you'll know what you compression ratio is when it all goes back together. Best of Luck!! Mark