Timing belt or chain?
 

So does the HHR have a timing belt or Chain?

chain

How often do you have to service it?

you don't. Timing chains usually last the life of the engine and do not need to be changed. Read the manual and I'm pretty sure it isn't mentioned to ever change it.

Thanks

I'm guessing that we have an interference engine though, right?

interference engines use a rubber timing belt.

Nope not true

My sports cars are non-interference and use a rubber timing belt.

My Subaru is interference and uses a rubber timing belt.

What the timing belt/chain is made from has nothing to do with if it's interference or not.

There are two types of engines that use timing belts. They are described as: "Interference Engines" and "Non-interference Engines" The difference lies in the proximity between the valves and the pistons. On an interference engine, if the timing belt slips even one notch, the piston can crash into an open valve causing serious engine damage by bending valves and breaking pistons. Non-interference engines will usually not self destruct, but in either case if the belt fails, the engine will immediately shut down leaving you stranded.

Let me be a part of the "Chain Gang" anyday.

Chains break too with the same result if you have a interference engine.

Again the question is are our engines interference??