*** IMPORTANT ***
Be Aware In Regard to the K21/K25 Engine
Although the engines come with timing components, these are only meant for TRADITIONAL DISTRIBUTOR SYSTEMS.
All Timing/P.T.O gears and chains on the engine are for testing performed after production. All engines are spun tested 3 separate times with 8 hours performance cycles to document accuracy and compliance of all specifications.
If your truck uses an ECM System, you MUST remove all timing components that come on the engine and transfer all the timing components/P.T.O over to mate with the engine control module.
You MUST use the crank trigger gear and distributor delete adapter from the old engine and install it on the new engine.
Please make sure after transferring all existing components and chains that you set the timing marks properly.