GM made two variants of the 4200.
'02to'05
'06 to end of production.
There were many small improvements made each year but in '06 the biggest change occurred:
New head with bigger intake/exhaust valve, longer valves, better valve springs and retainers.
Higher compression and redesigned camshafts.
The exhaust port was redesigned to allow the engine to breath better. A new aluminum valve cover and VVT actuator was introduced.
Last edited by efi-diy; 02/17/09 02:24 PM.
