Not sure what you're measuring.
The flange bolt patterns (between centers) are S.A.E. industry standard, not Rochester or Chevrolet.
Small (216, early 235): 2-11/16" (2.6875"), large (late 235, all 261): 2-15/16" (2.9375").
The 216 throttle bore is 1-1/2" (1.500"), 235 is 1-9/16" (1.5625"), 261 is 1-11/16" (1.6875").
Panic - you got me, now I don't know what I was measuring either! Here's todays "update" . the bolt center to center is 2.6875 (ish) using calipers measuring outside to outside of the bolt studs and subtracting the OD of the studs ( major diameter of threads is .368" ) , used .375". The bore really is 1.500". So that's 216 CI data and so then I looked up the intake manifold casting number 3835527 and found that its for a 216 motor. That casting number corresponds to a part number 3691933, Group # 3.265 and its application is 1950 - 1953, 216 all. Hmm...and a long exhale. Guess I need to find the correct intake manifold? After all, I have this shiny rebuilt ( although suspect ) carburetor from Autoline. Your thoughts?
