Checking a vortech head unit.

[Cobraman]

What defects should I check for before buying? How can I tell if it's in good shape?

[Broncojohnny]

Any beat up fins on the impeller? Does it spin freely and not hit the volute? Check for oil leaks around the drive shaft. An oil leak there can mean some bearing wear. The things are easily rebuilt, the cost of bearings is the biggest expense.

[Captain Crawfish]

your best bet is to rebuild it with new seals bearings if you have the cash. if not just check what al says and run it. they are very reliable units. also pull the front cover off your 4 v and install new chains. over time they will get some slack in them and the blower will stretch them more over time. once the tensioners are all the way out they dont take up any more slack which can lead to problems.