I am in the process of installing a new 331 shortblock that my builder installed a Crane Cam. The intake duration is 224 degrees and .542 lift, exhaust is 232 degrees and .563 lift with 1.6 ratio rockers. I have valve springs with a max. of .600. My question is: Is it safe to use my existing 1.7 ratio rockers or should I go to the 1.6 ratio? I asked my engine builder and he said it's not a problem to go with the 1.7. Doing the calculations I'm coming up with about .598 lift on the exhaust which is real close. I appreciate any advice in advance.