You gotta see this ......

Yes really. Edelbrock is full of crap on the requirement. If you ran a stock 340 cam with ede heads/spring would an aftermarket/adjustable rocker be required, I think not... actually I know it's not.

I've run a 508/509 hyd cam with stock rockers and a slightly heavier than stock spring. Once you get to about 300# over the nose, the stock rockers will start failing. That's why I'd be interested which cam the OP installed. Anything under about 500-520 lift is typically OK.

Valve to piston does not differ between the garbage 340 open chamber head and the closed chamber piece Ede produces. Valves are in the same spot, only the chamber is opened up.

Nothing I posted in this thread is or was directed at any individual poster. If you took it that way, relax a bit. Those instructions are ridiculous IMO.