MopaR&D
Nerd Member
I am looking at cam specs for calculating my dynamic compression ratio in my 360 LA with Magnum heads and noticed something that doesn't make sense... Dynamic compression is based off how late the intake valve closes after BDC, and the specs for "similar" cams between manufacturers seem to be vastly different. My current Lunati Voodoo 256/262* cam has an intake closing of 34.5* ABDC and gives me a dynamic compression of 8.7. I want to put in a longer-duration cam to bleed off some pressure at lower revs as my engine has 10.5:1 compression with the .060"-over KB flat tops and pings under certain circumstances (hot days, lower octane gas, etc.). The popular Voodoo 268/276* cam has intake valve closing at 39* ABDC and drops the compression only a little bit to around 8.55. However looking at the similar COMP XE268 cam the intake closing is a whopping 60* ABDC!! What the heck is going on here? Using that cam my dynamic compression would drop to the low 7's which would be lower than I need. Am I missing something here or are the cam profiles really that different across manufacturers? And would changing to the 268 Voodoo cam make any difference in reducing ping at lower RPMs?