Hi i have a 99 silverado with 83k and have a terrible knock when the engine is cold but when it warms up, no knock at all and the engine performes great, I had a procharger supercharger on this engine for about 18,000 miles when i heard the knocking we took off the supercharger. So i was thinking about puting in a new engine and was wondering if a 6 liter would be a simple swap for the 5.3 that i have now, Thanks..

 

yes it is a direct bolt in as long as u get the same year engine, the knock you are hearing may just be piston slap, it happens on cold startups your call on replacing, but may as well prepare and drive it till it dies
*edit*- also if you install the 6.0L u will need an engine tune

 

Is it a knock or a clicking?

 

Are you using heavier oil than is called for in your manual? If so return to the proper weight.

 

also, sythetics take care of many start-up issues as there is instant oil pressure intead of a gradual build up

 

I have the same issue with mine it's a 4.8L. I have owned it since 52000 and I have 116000 on it now. The knock is piston slap. I run 10w30 or 10w40 high milage oil with conditioners in it. I tried using the recommended oil. The knocking is worse and it uses oil about 1.5 qts in 1500 - 2000 miles when running the lower weight oil. Just my experience though.

 

im using synthetic but would a thinner oil help or make things worse???

 

worse

 

When it starts to get cold out the knock gets worse for me, had it even brand new. Not sure what part of the country you are in but I have a block heater in mine and when I plug it overnight it keeps the oil nice and warm. Gets that oil pumping fast. Might want to give that a try.