OK ! The "848" head was the head that Chevrolet made for production 235 engines beginning in 1958 through the last year of production for 235 engines, 1962. "848" has become the "term" used to describe that certain head that has the casting number which ends in the numerals "848".
The casting number appears on the driver's side of the engine on a "ledge" of the head which is not covered by the valve cover near the line of head bolts next to the valve cover closer to the front or the left side of the head as you face the left side of the engine.
The significance of the "848" head is that of all of the 216, 235 and 261 heads, it is the one with the smallest combustion chambers thus giving it the highest combustion ratio and makinge it the most desirable of the heads for 235 and 261 engines because it can deliver more power than any of the other heads.
As a side note, it will also produce the loudest exhaust sound, when coupled with headers or a split manifold and glass packed or straight through mufflers, of all of the heads because of that high combustion ratio.
Check the left side of your engine head. I have seen so much grease, oil and crud on some engines you can't see the casting number until you scrape all of the gook away.
Good luck!!!
