1950 Chevy 1/2 ton rocker problem

[William Stewart]

A while back, in "Stuck Valves/Bent pushrods", I wrote about this problem and you guys came up with some good suggestions. The valves were soaked in carb cleaner and worked free with a spring compressor pushing on the stem until they were moving like they should. Then I got Marvel Mystery Oil on the stems (No A&P mechanic is without this stuff) and set the clearances, and was off and running.

The truck has been back on the road with a temporary cabin fuel tank and fresh gas. Yesterday morning, on start up there was a loud ping followed by rough running. The #6 intake rocker broke on the pushrod side. I don't know yet if the valve is stuck again or if the rocker was overstressed by the original stuck valve (the pushrod isn't bent).

I need a replacement rocker for a 216. The Shop Manual calls it a LH-IN, which is PN 839463 and it should me marked 5. It has 57 cast on it. No Stovebolts in nearby salvage, so please recommend a good source for this part. The engine SN is JBA 36203.

Also, the Manual sets the spark at 5 degrees before TDC. Any recommendations for modern gas?

Thanks for the help so far, Bill Stewart