max valve opening

[reds89]

can you guys tell me on a set of pro1 heads, it says on the info that max valve lift is .520[single spring heads],does this mean that this is max lift with all clearences factored in or do i have to run a smaller cam with .060 less than the .520 for safety.
If .520 is max lift with the safety margins already in is it wise to go to that full .520 or stay a little less.
Hope you can understand what i,m getting at,this the first set of aftermarket heads i,ve used and at 58 years old the brains a bit fuzzy.
Thanks for any help ya can give me.

[69Merc]

the .520 max lift is with all clearances factored in. However, i would not recommend pushing the valve spring to its limit.

hope this helps!

[reds89]

thanks for that 69merc,i will take your advice on that,thanks again bud.

[Awesome Bill]

when it says .520 lift, this is what the spring will handle safely. We run the valve spring within .040-.050 coil bind and really don't care what the seat pressure is with a roller. The more the better. A flat tappet camsshaft will live longer with the EDM hole and 15-25 lbs of seat and open pressure. We usually use 140-170 and keep it under 425 with EDM lifters and 130-150 and 375 open without! The spring likes to be kept in its upper limits not lower!