340 rocker arms

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Ollinoboys

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We bought a short block which included X-heads with springs and valves installed. I want to get new shaft and rocker arms. But I've never seen them assembled and am not familiar with SB Mopar engines. Any advise on where I can get illustrations or videos on assembling them? I don't know if spacers or bushings are required or where to find the correct parts and set up.
 
It depends on which rocker setup you use. The stock paddle type rockers don't have anymore spacers than what the stock hold downs are.
 
Ollinoboys said:
We bought a short block which included X-heads with springs and valves installed. I want to get new shaft and rocker arms. But I've never seen them assembled and am not familiar with SB Mopar engines. Any advise on where I can get illustrations or videos on assembling them? I don't know if spacers or bushings are required or where to find the correct parts and set up.
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Use the search box here. I bet there's a hundred threads about small block rockers with lots of photos.
 
340 rockers are slightly different than others to deal with the 340 springs and slightly higher lift. If you flip them upside down, you will see the machined area for spring retainer clearance.
As I recall it, they are also slightly more robust above the rockershafts, but you almost have to mount them side by side with 318 rockers to see it. But the machined areas are the obvious indicator.
Every cylinder has a left and a right arm with offset pushrod cups to center the arms over the stems.
If you don't already have arms, then it's only a few bucks more for quality aftermarket arms and you get to upgrade to 1.6 ratio units, which, after installation,might actually be closer to 1.6, compared to the stockers being closer to 1.42. And that means over 12% more lift or ~.057 on an advertised .450 lift cam.
Course on a stock Iron head you, now you are at .507 and you'll probably have to machine the guides to make room...... on and on it goes,lol.
The shafts have a very specific mounting to make sure oil get inside them to lube the arms. When you check them out you will fine a lil notch on one end, and on the perimeter of the end. That notch goes to the left and down. With the heads on the engine, this means; to the firewall on the passenger side, and to the rad on the drivers side. If you take the time to examine the shafts you will see why this is important.
 
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AJ/FormS said:
If you don't already have arms, then it's only a few bucks more for quality aftermarket arms and you get to upgrade to 1.6 ratio units, which, after installation,might actually be closer to 1.6, compared to the stockers being closer to 1.42. And that means over 12% more lift or ~.057 on an advertised .450 lift cam.
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Be careful with this information above... I've measured out the stock rockers by themselves at 1.48-1.49. People get the lower numbers of 1.44-ish when the measure from lifter to valve.. .but that includes the pushrod angle loss, so is not just the rocker.

That same pushrod angle loss will occur with all of these rockers... so that 1.6 will now be 1.54-ish. Plus a roller will have losses that the stamped rocker does not have, at the roller end. So now you are back down in a 1.52-ish range range for that 1.6 roller. So you're at 6% more lift + or -, not 12% more... but right where you wold expect to be.
 
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