Re: Torque and Power Curves for S-10 4.3L
From what i have heard about the problems that the small blocks had it only made the knocking when it was cold and they were really bad thi time of year when the temp was below 40 degrees. If the noise is that loud then it is probably not a spark knock. My friend has a 98 sonoma with a four cylinder thats makes a knocking when it is cold but it not that loud but it has done it since the day he bought it the dealership told him it is nothing to worry about.(so he does'nt but any noise on a new truck would bother me.) If there is a bad sensor it should throw a code but a computer maybe still able to help you.
other then that i have know idea without hearing it.
best of luck with it