Please post the numbers of the existing engine: model, type, and code. This will help in determining details such as existing crankshaft diameter/ length and fuel tank size. The engines you listed have different crankshaft diameters. The OHV engine is heavier.

The engine on the Snapper HiVac was a tight fit and in some cases, a custom fuel tank was installed to clear the bag chute. Also, some of these used the 25 MM crankshaft. New Quantum engines meet tier 3 emission standards and no longer have the idle speed circuit in the carburetor.

Personally, I would opt for the Quantum engine. Been a great engine for more than 20 years. The OHV engine is also good, and has better fuel economy and emissions.

In addition to outline dimension issues and crankshaft diameter, also make sure the engine you purchase is a "compliance" engine with flywheel brake. The IC motor definitely has bowden connections for the flywheel brake. Not sure about the other Quantum. The IC motor also has the iron sleeve which I consider an added advantage.

ggoyeneche, Thats pretty much what i was thinking. The Quantum is just so simple and reliable. I've put so many hours on similar units. I just wasnt sure if the OHV was clearly WAY better than the flatheads.

I'll try to get the engine info soon. The examples given are just an example of the types I'm looking at.