Don't know, exactly, but all the data I have matches that. In 1961 GM stated the 235 produced 135 hp at 4000 rpm (except for the economy version) and the 261 produced 150 hp at 4000 rpm. The 235 had a compression ratio of 8.25 to 1 and the 261 had 8 to 1. As for torque, I've never been able to find a GM published number or curve for the 261, but I do have a GM produced hp/torque curve for the 235 dated 1958 (attached). I suspect Tom Langdon knows this or could find it.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
