For GM / General Motors.
The camshafts must be held at TDC to properly set timing, especially once the inner timing chain is set. Both camshafts on each head must be held to time either head in turn. The camshafts on the left head must be held while timing the camshafts on the right head. During this procedure, the left head camshafts are under spring pressure, and can cause the cams to turn, leading to mis-timing the engine. On the left head, EN-48383-1 is installed to hold the cams, and timing is set per published service information. When the engine is at the second timing position to set the right head chain, EN-48383-2 is installed to hold the left head cams, and EN-48383-3 is installed on the right head cams. Both EN-48383-1 and EN-48383-2 are slotted to allow them to be installed over the SIDI drive portion of the camshaft in future applications. Failure to use EN-48383 can result in incorrect timing, leading to engine damage.Email