[grumpyvette]

most sbc factory heads will allow a lift of about .470 with the factory springs and clearances, a few will allow up to .530, but the only way you can be sure is to verify clearances, I see guys install new high lift performance cams using the factory springs and never verify the clearances then they are amazed when things go badly

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=181

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=282

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=501&p=11829&hilit=radial+clearance#p11829

using a valve spring micrometer and measuring spring bind helps verify clearance


the result of not verifying valve train clearances,full lubrication and valve spring load rates