Bert,
I calculate that the Cadilac 261, with a 4.125" stroke and 3.750+0.050" bore will be 281 cubic inches, about 1% above the 278 for Tests 7-9 of the McGurk article. At the rpm range that you will be running, a cubic inch is a cubic inch. A few months ago HRM reported on some dyno tests, on a BBC, where they tested different combinations of bore and stroke that gave the same total displacement. As I remember, there was very little difference in the performance.
If you plot the torque versus RPM for the McGurk tests, you will see that you really want a better than stock cam. See what Tom Langdon (or other members of this board) recommend. There must be something better than the McGurk No. 18 grind now. I've always liked to look at torque vs rpm rather than HP vs rpm, as the curves are not distorted by the rpm effect on horsepower. It is much easier to see where the torque starts to fall off, and what combinations of cam, carburetors, etc. really do for your desired operating range.
Keep us posted on your engine - it is a great project.
Hoyt, II# 922
