[64play]

1969 063 heads, how much lift will they accomodate? Is .520 overdoing it?

 

[rustbucket79]

Given the heads are 42 years old, you absolutely need to check them, both in lift tolerence, but also seat and open pressures. (don't want to wipe a cam or float the valves)

For bone stock single springs, it's tough to achieve .500" lift and still have sufficient seat pressure. Even the LS-6 springs are close at .500 lift.

 

[mr 4 speed]

FWIW,stock springs are lucky if they have 90 lbs. on the seat

 

[johnretired]

I once put a .547 lift GK cam in a 335HP 427 and it woke it up and wore out the springs in quick time!
It got so it wouldn't run past 5200!!!
But it ran 160 mph with it for a while.
I was a dumb kid!!! Glad I survived it.
BTW, I used the stock springs.

 

[dt]

Change the springs. Period. :thumbsup: