i have a 1988 chevy s10 blazer 4x4 4.3 l v6, i have a knocking sound coming from the engine which only has 30,000 miles since rebuild. vehicle overheated and blew a head gasket about 6 months ago which i replaced by pulling both heads, machined them and rebuilt them. Therefore I did a complete head job. vehicle ran fine for about 1500 miles then all of a sudden started knocking in the engine. Sounds like to me its in cam shaft area and not low end, did not replace lifters with head job. Runs and drives great if i retard the timing the noice starts to go away, but of course vehicle runs like a dog then. I was told possible knock sensor...any advise would be very appreciated. thanks Jason

 

A "knock" is typically a bottom end problem while a "tap" will typically be a valve train issue.

Did you get coolant in your oil? If so, how long did it run like this? You may have washed a bearing and damaged it...