Originally Posted by Bluepen
OK I am totally messed up on this and it most likely is very simple except to me.
'78 sbc 350, stock castings, unknown if milled, small cam, stock rockers and rods, did not build this motor the PO did.
Now I got a set of cheap stamped steel valve covers and some of the rockers hit the intake side of them not the top. OK they are stamped steel and I wasn't suprised at that, a few taps with a hammer, fixed. Now I've got a set of GM Performance cast billet aluminum covers, good set. But I have the same problem, some of the rockers are hitting the intake side of the covers on both sides. I thought maybe wrong rockers or rods because I didn't build the motor. I went to the parts store and pullled new ones off the shelf and they match perfectly. The rockers are sitting in the center of the valve stems so this is where I'm lost.
Can anyone tell me what might be wrong in this picture?
Unfortunately not really sure. If it isn't an issue of where the heads center on the cylinder bore, they make and sell offset alignment pins for the purpose. It could be the the pushrods aren't the correct length causing the rocker to sit low on the pushrod side which might get it into contact with the cover. Last idea would be the studs are located incorrectly either in position between the E and I sides of the head or that they are bent toward the intake side.
I'd start with pushrod length and vertical squareness of the rocker studs as it takes observation and measuring rather than major disassembly, some disassembly but not of heavy stuff. Go to the comp cams web site, they have a good tech article on how the rocker should address the valve stem. The latter situation can be caused by one or several of these factors 1) head milling, 2) block deck milling, 3) long stem valves, 4) larger ratio rocker arms 1.5 to 1.6 for instance, 5) roller rockers that simply occupy more space, 6) short push rods, 7) incorrect lifter length or adjustment resulting in the lifter height seemingly to be too short lowering the pushrod, 8) cam lobes out to lunch lowering the lifter and pushrod which will drop the rocker too straight so it might scrape the cover.
OK, it's late and I'm out of ideas, this ought to give you some food for thought, however.