on the 07 5.3, are they pushrods or cams? and how can you tell which motor is which? and what makes one better than the other?

 

5.3s are cam-in-block OHV engines.

2007s are 5.3s.

 

The implementation of the OHC (Overhead Cam) technology eliminates the heavier parts of the valve operating system. Therefore reducing the weight/resistance that the Valve Springs have to deal with, to open/close the valves. This does three things...

Enables the Engine (when properly set up) to achieve much higher RPM.
Reduces the cost of required operating components.
Reduces the weight of the engine assembly.

 

OHC also adds more complexity and usually increases physical size of engine.

 

OHV with hydraulic lifters offers better low end torque and HP while OHC really come in at more specific rpm ranges.

 

OHC engines can require more maintenance at specific intervals. Some timing chains require changing at 60,000 or 75,000 miles. With push rods, you just have to ensure they are getting proper lubrication. Occasionally a hydraulic lifter may collapse. With that said, most OHC engines are interference engines* while most push rod engines are not.

*An interference engine is one that the piston and valves are so close together that if there was a timing issue, a piston would "kiss" a valve. With a non-interference engine, if the timing was thrown off, the valves and pistons would not touch.

Example: For a lot of Saturns (GM product), if your timing belt/chain broke, you would also need to replace the head. There was a big enough market for this, that rebuilt heads are readily available for around $300.

I was fortunate enough to own an '98 Isuzu Trooper (also GM) that, despite being OHC, was not an interference engine. If the cam chain broke, just reset the cam shafts and engine crank to TDC, and install a new chain, water pump and chain tensioner.

 

When my lower crank gear shed some of its teeth, the timing chain stopped and bent three valves. That would lead me to believe that the 350 L-82 engine is an interference engine.

 

I'd have to agree with you on that one! I don't know specifically which Chevrolet engines are interference/non-interference. From my (limited) experience, I've seen a tendency to be more interference engines with OHC technology.

 

According to Rock Auto, at least for 2004 there's an international version of the 5.3 that is OHC ... but the ones sold in the US (the Flex Fuel one anyway) is OHV / pushrod.

I like pushrods better anyway. Old school mature design, reminds me of my old Harley.