sbc spark knock

It might be the cam.........

If it has early closing of the intake valve to get "more power under the curve"(whatever that means) it may be building a lot of cylinder pressure causing the knock. Hey...I'm no cam expert....know just enough to be dangerous. Really need to know the cam specs/particulars to help diagnose. I would try all the above to see if you can stop the spark knock. Start by moving the initial timing back. Then experiment with the vacuum advance. try ported and unport vacuum. See if either makes a difference. With the initial advance back some...try some lighter springs and see if the total timing can get to 34/36 degree by 2500rpm...withOUT knock.
6sally6

This has been discussed many times.There are at least 4 different balancer and timing mark location on small blk chevy,Has the balancer slipped etc.How many cc are the heads, is it o deck

Good come back........

IF he used an old balancer it could have indeed slipped, therefore, the marks are off and engine possibly out of whack! I WOULD HAVE spent a little more and got a new(or known "good") balancer and had the assembly..including the balancer balanced at the machine shop while they were doing the work. Just eliminates "things" that could cause problems later.
6sally6