Re: GMC/Mercruiser 120 Valve Arrangement
Iron Duke is a nickname that's been applied to Several Different little 4cyl. motors,<br />by Several Different groups of people.........
Not sure about
several different groups . In this case, you must have a 2.5L GM 4 cyl engine.
It is called the "Iron Duke" to differentiate it from the
all aluminum 4 cylinder engine that GM developed and used in the Chevy Vega. That motor had serious (fatal) reliability problems. So GM took a 1960's era Pontiac 153 CID 4 cylinder engine and used it in the last Vegas. They called it "Iron Duke" since it was all iron.<br /><br />As far as the valve arrangement goes, I do not know how they are arranged. But if you look at the exhaust manifold only (yeah, I know the intake manifold is on the same side), you should get an idea. If the valves go the way Bondo says (and that's a good guess) there will be two exhaust ports in the middle of the manifold right next to each other. Like a small block Chevy V-8. If the exhaust ports are all evenly spaced (like a Ford V-8) chances are the valve arrangement you guessed is accurate.
