Make sure the pushrod cup is getting oil. There is a hole drilled through the adjuster boss to the inside of the rocker arm. I have had used 273 rockers were those holes were partial to totally blocked with crud. Make sure the holes are clear and the adjuster screw and inside threads are clean of crud.
Also for the adjustable 273 rockers they oil the pushrod cups better if you use the shafts that have the banana groves and a second oiling hole that lines up with the hole for the pushrod cup oiling. Shafts designed for the stock stamped hydraulic rocker arms have one large oiling holes on the bottom and do not have this secondary oiling hole and you risk getting less to the pushrod. See pictures of the stock 273 shafts with the two holes.
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