fresh rebuild - just checking if this is normal
 

Hi all. Just rebuild my first NA engine, and got it running and idling pretty good. It's holding idle at 1200 with the idle screw all the way closed. I heard that is normal, and that as it gets all wore in the idle will drop. I'm pretty happy as for right now it has 85 compression front, and 92 rear. (highest compression motor I have ever had by FAR)

What I am concerned about is that my exhaust sounds a little weird. I just have the exhaust "header" on with no exhaust as I have to get my turbo exhaust modified to fit to the NA. But every few seconds, I get a little POP, and the engine shakes. It seems random, and it seems to me like it is just the mixture not getting ignited at the correct time and igniting later. I have been told I can't check timing until I get my idle under 1000, but I have my first mark on the pulley aligned with the mark on the cas, that is as much as I have done with timing. Could I have it 180 backwards, or is it this normal for a rebuild? Maybe it is normal for 13b's in general, but not having the exhaust on just makes it really easy to hear?

Thanks all.
~Tweak

(P.S. I should have a video uploaded later today)