I've been doing valve clearance today. It's been a while, and I could hear a slight tick.
I set them at 0.018" warm. Thinking it might give a little more overlap that wouldn't hurt. There were still a couple that were making a little noise, so tweaked then a bit more. Thinking it might be wear on the rocker tips.
Hopefully that's all good, and any comments welcome.
I was wondering if it is normal for some rockers to be off centre from the valves quite a bit?
Grateful for any feed on the subject. 

Totally normal for some of the OEM rocker arms to sit off center in relation to the valve stem.  That is why the rockers have the extra wide pad.  Having the extra wide pad allowed the engineers to use a single rocker arm for all the valves rather than having specific lefts, rights, and possibly centered rocker arms to position a narrower pad over the valve stem.  If you have worked on the LYB engines, you will notice that those engines do have specific left and right offset rockers.

Lorena, Texas (South of Waco)

Thanks Ted for enlightening me.
Surprised they are not shimmed on the shaft to centre on the valve. Would that upset the geometry?

I have seen others have shimmed the shaft to center the tip of each rocker arm over the valve; my opinion is that it is really not warranted but to each their own. My estimation on why Ford did it this way was to save the cost of hardware. The bean counters must have run the numbers on millions of Y blocks and figured it was a cost savings to allow each rocker arm to be the same. Like Ted says, the engineers could use the same rocker arm for either intake or exhaust... must have made the budget oversight committee happy.

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

"I have seen others have shimmed the shaft to center the tip of each rocker arm over the valve ..."

If that is done, it will upset push-rod geometry.

The reason(s) for the offset rocker pads is due to the stacked runner system used on the FYB and the need for valve-train clearances.

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"There were still a couple that were making a little noise, so tweaked then a bit more. Thinking it might be wear on the rocker tips."

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The problem that arises when attempting to center the OEM rocker arms on the valve stems is that the pushrods no longer center within their respective holes.  If the pushrod contacts or rubs within the hole in the head, then there is a strong possibility that this will prevent the lifter from turning which in turn causes the cam lobe to go flat.

When switching over to the roller tipped rocker arms, there are specific left, right, and centered rockers that allow the pushrods to be centered within the pushrod holes in the heads.  The combination of offset rockers for the iron heads differs from what is used for the aluminum head due to the difference in valve spacing between the two styles of heads.

Harland Sharp rockers on iron heads.


Harland Sharp rockers on aluminum heads.
  

Lorena, Texas (South of Waco)