I have a knocking in my engine. on 2002 Chevrolet Silverado 2500 HD

When accelerating my engine I have a knocking sound, I had the top end cleaned at the dealer and they say I need to have this done every year at the cost of 500.00 per cleaning. They also say this is normal for chevy's.

The price you paid for a "top engine" cleaning seems to be on the high side. I am not sure exactly what the dealer did for that price. If the noise is now gone that is a good thing. A bottle of fuel treatment such as "techron" every few months may help keep the deposits from building up on the valves and pistions.
2 more answers
Knocking is normally due to low octane and experienced when accelerating or climbing hills or anytime the engine is under a load. Arizona being one of the "Greener" states uses oxygenation of gasoline and other "green" technologies which can reduce the real octane rating of your gas. Some stations now use nitrogenization as cleaning method, avoid it, as it is really only a filler giving you less gas for your money. As for cleaning, run a bottle of STP Full System Cleaner through every 6-10 thousand miles, not any more often as the naptha content can cause damage. After running the cleaner, run a bottle of Lucas Gas Treatment or Marvel Mystery Oil, this helps lube and condition seals. The Lucas and Marvel can be run more often. Run higher octane gas or put an octane boost in, using a booster is a little less accurate for measurements so skip every few tanks especially if you refill before empty. Lucas also claims, although I have no proof of it, to raise octane and to be safe every tank, but can be more expensive than a cheaper booster. So, Buy good gas, keep octane higher and clean regularly, I have done this for years and have never had a knock or had bad seals or dirty injectors.
i have one that has 167,000 miles on it, it started knocking off and on say once every two weeks for about five miles an stop, and when it needed an oil change. On my last oil change they put 10w 30 instead of 5w 30 it starter ticking really bad. I have a brother-in-law thats a real good sert. mach. he says it the hydrylic lifters loose prime with the thinner oil will find out in a week if its true. i gonna do a topend rebuild sometimes this week 7-3-10!