Quote Originally Posted by ontarian_frog View Post
Take it to the dealer and have them inspect the timing. Rough idle is normally a sign of the timing being off by a tooth.
nail on head.. sounds like your local chevy dealer screws a few up too though, by passing that info along. Ask to know which dealer they called to verify what the said and that you want them to fix it and show you its in time by the marks..

problem i see is when you turn the water pump, you lose time, you need to account for that before hand. then recheck the marks after its tight.