Gotha cast iron rocker arms are mentioned in a lot of the early-'60s Slant-6 buildup articles. A few years ago, I found a set, new old stock in a mouldering box. Snagged 'em, cleaned 'em up, and thought I'd post some pictures.
The box says "1960-62 Valiant Lancer Plymouth Dodge 170 225 6cyl 1.6 ratio Intakes Only". I'm not sure why the admonition not to use them on the exhausts. Perhaps the thinking was that rockers like these would only be used with a camshaft much biggger and compression much higher than stock, and using these 1.6:1 rockers might cause the exhaust valves to smack the pistons...? Seems odd, to me.
I might've installed them on my car the last time I had the top end open, but I noticed that these rockers have only one oil passage, from the shaft bearing rearward to the adjustor/pushrod area. There's no oil feed to the front of the rocker. Seems to me this would tend to starve the rocker tip-to-valve and the valve stem-to-guide junctions, but I'm not sure. I also thought to add the missing passage, but that seems like very delicate work, and I'm not familiar enough with casting intricacies to assess the risk of breaking or otherwise ruining a rocker in the attempt to drill the forward passage.
So, here're the pics:
That would have made a nice street rocker if it had proper oiling. Too bad something like this will never be made again due to tooling costs vs sold units.
