509 in a 440
 

I'm wondering if I can safely run a 509 in a 78 440 with flat tops? The block is stock deck and the heads are massaged 906's. Would I have to clay the heads to find out?

440 or 509 makes no difference The valve clearances change depending on the cam not the size of the motor

You need to clay it. Only way to be sure.

I'm not sure but in my experience the lift is not the usual problem, it's when the duration gets big and contact happens when the Intake valve is "chasing the piston". There are ways to do it with the head on but claying the piston with a solid lifter through two full rotations is best.

X3 on claying it.

big cam in a low compession smog motor, bad idea

I put a 509 cam in my 77 440 motor, and the stock cam worked better! Thats because the 509 loves compression, gears, and hi stall torque converters. Ha ha. But it was a used cam and I wanted to try it in an older motor to make sure it didn't have any probs. I had to go from power to manual brakes though because of poor vacumn with the 509. Thats common. So now I put the cam in my 12.5 to 1 C/R 451 and it screams! Thats a great cam, and still quite popular after all these years. Oh the 77-440 had 906 heads, dished pistons, and the Ross ones in the 451 have valve reliefs, so no probs in either engine with piston to valve clearance. Same heads both motors.