Junk 842 Aluminum Heads

[VintageMusclecar]

Eric;

I don't know of any reliable way to ID an open chamber head from a closed chamber just by external inspection.

As far as the "open chamber" 842's, many were converted from closed chamber into "open chamber" back in the day by relieving the plug side of the chamber wall. Old-school racers trick trying to improve flow & flame travel before true open chamber heads were readily available. I've seen many closed chamber heads with this modification, even some cast iron ones. Somewhat risky mod though, as the chamber wall by the plug isn't that thick. You can only safely get about 1/2 way to an "open" chamber before the chamber wall starts to get too thin. Still helped flow & flame travel somewhat, at the expense of some compression & quench area.

Eric