Dave, I've been working with these engines for years. They have the same block as the '62 thru '70 Chevy II four-bangers, which is 2/3s of a 230 six. They are NOT an Iron Duke, although the later Iron Duke was derived from the old Chevy II engine. Iron dukes are 151 cubic inches and Chevy II engines are 153 cubic inches. The 120 HP Mercruiser engines have the same head as the Chevy II engines. They have a variety of carbs on them, including two Carter single barrel carbs. The 140 HP versions are bored out to 181 cubic inches, have a different head with better breathing and also have a variety of carbs on them. The 181 is the most desireable to anyone building a light hot rod, or lakester. I had a souped-up 120 Mercruiser engine in a Chevette and it was a snappy performer. I presently have a 153 Chevy II engine from a '70 Nova in my Model A. Where do you live? I'm in central PA. I might be interested in the engine, or parts from it, if you're not too far away. If you're interested in selling it, or just want to talk about these engines, e-mail me at drh@digital-link.net
