Quote:
Originally Posted by Murphy
Could someone give me the casting number and conbustion chamber. Thanks
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Depends on the year. According to NHRA specs '68-'69 used 3911032 or 3927185 with 65.5cc combustion chambers, '70 used the 3927185 only with a 63.3cc chamber (?), and '71-'72 used 3986339 or 3998991 with a 66.1cc combustion chamber. These are all small port heads, like a 283 head, and use 1.72" intake and 1.50" exhaust valves.
1973 is an anomaly. That year the 307 is shown using 333881, 333882, 3973493 and 3998993 heads. The specs also show 1.94" intake and 1.50" exhaust valves with the same 66.1cc combustion chamber as the '71-'72 heads. These are normally considered "350" heads with large ports and a wider combustion chamber. I could easily doubt that those are the correct production heads since Chevrolet did not use those large valves on small bore engines (except the '60-'61 283 high perf Corvette engines). Maybe another gift from the NHRA tech department and an errant data entry person. But, being legal doesn't always mean being "right".