Another 273 cam question.

I agree that cam is too large for the converter. One step down though would work well.

What these guys are trying to tell you is, your engine was RATED at 9.2 compression, but it IS NOT actually 9.2. It is more like 8.5 at best.

Chrysler's deck heights were very tall compared to the "nominal" spec. Nominal is a fancy word for "about". In other words, there's a RANGE around what the spec is, and Chrysler's deck heights were always very tall......and usually crooked and that cut way down on the actual compression ratio.

Also the actual combustion chamber volume was usually always larger than spec, leading to even more compression loss compared to the rated spec.

This is why when a professional builder builds an engine it gets"blueprinted" to a certain spec. Blueprinting means adjusting everything to a certain spec, such as those used by the factory, or a set of predetermined specs the builder and or customer agree on to achieve an actual compression ratio.

Can you imagine the added cost to cars had Chrysler blueprinted each and every engine they built? It is always best to "assume" the compression to be lower than the factory spec if the engine is still in stock condition regarding piston style and cylinder head configuration. This way, it will be less easy to over cam the engine.