Popping like sound

[gearhead]

I had one doing this in my shop this week it was the injector it did same thing poping like jake on. It was so bad you couldn't find it with cutout test. I used temp gun and found it 100 degrees hotter at 700 rpm on #3 cylinder. I put this injector in # 4 and it followed injector. But what i did do when rockers where off is take a air blow gun and stick inside the cylinder with valves closed of course rockers are off and push air inside of the cylinder. If you have valve problem air will bleed back through either intake or exhaust and then you will find it.