Originally Posted by cobalt327
When you get the heads off, put the engine on TDC and measure that cylinder's piston depth from the block deck to the piston deck. This can be done w/a depth micrometer, the depth measurement of a caliper or a straight edge and feeler gauges.
Then flip the heads upside down and the leveled head's chambers are filled with a 50% rubbing alcohol/50% water mix (to lower the surface tension, or water alone can be used) w/some food coloring added.
The head's combustion chamber is covered w/a clear piece of plexiglass w/a small fill and vent hole so the bubbles can be seen and 'chased' out the vent (or use a CD w/the plating removed by scraping the plated side 'backwards' w/a razor blade to pop the plating off). You use the cover over the chamber to keep the surface tension from fouling the measurement. A thin layer of grease or vaseline seals the cover to the deck. The valves are left in w/springs to hold them shut and a spark plug is installed as well, so the chamber will be watertight.
The piston voulme will almost always be published by the manufacturer, so with all that info and the head gasket compressed thickness, that will give you the static compression ratio.
Once you know the CR, you can then go about deciding on a cam or on what mods need to be made to run a cam you might have already chosen.
That fluid Cobalt is referring to as the 50/50 mix is often sold as the blue windshield washer fluid, you prob have some in the garage.
You need to tear the short block down too and probably need to check the bearings and surfaces for wear. Also the lifter bores should be checked if you're loosing cams as they can cause that problem.
Just to let you know ahead of time you're probably looking at a $500-$1,500 expense, between any necessary cleanup machining, new bearings and gaskets, new cam kit, cleaning etc.