I had the 5C heads on a 400 motor with Comp Cams Rockers and BBC studs. That was the motor from my black 67.
I was having issues with bending pushrods at high RPM soon after I bought it and was breaking up after 4k. After 3 bent pushrods, I pulled the covers and tried to re-adjust after buying and installing the new pushrods.
Problem was the pushrod length was stock and was not allowing me to adjust the valvetrain. I had to go to 9.375" BBC exhaust pushrods across the board to quiet the valvetrain. This was based on stock stamped rockers and bottleneck studs/stock nuts not being used with a stock pushrod length. When they changed out to Comp Cams rockers and studs, the adjustable height/length increased.
Some heads will have different deck heights depending on whats been done. You have to properly measure that length with a "pushrod length gauge" and can not necessarily rely on "stock" applications as far as pushrods.
When I installed a set of 46's, I had to decrease the pushrod lenght back to stock with the same rocker setup.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
