How do you compute compresion ratio? I always figured divide the cylinder voume in cc"s by scombustion chamber volume in cc"s. Would Really like to hear the answer to this one, thanks in advance. Bernie Steffen bstef@mchsi.com
Heres how I do it You need the following info head combustion chamber cc deck height piston cc gasket thickness bore size With our buicks the known values are 455 bore= 934 cc 455+.030=946 cc 455+.038=949 cc .040" gasket=10 cc .020" gasket=5 cc for every .004" the piston is in the hole figure 1 cc,so a .036"deck is 9 cc Now lts do a sample calc say we have a 455+ .030"overbore= 946 cc usind a .040" gasket = 10 cc the piston cc is 33,typical 71 piston deck is .044"= 11 cc and combustion volume is 68 cc add all the volumes 946+10+33+11+68= 1068 now this is the volume your compressing into the area above the piston,add those volumes 10+33+11+68=112 now divide this volume into the total 1068/112=9.54 CR hope this helps gary
