I have a problem and I am not sure where to start looking. I have a 302, GT40-p heads, 4100 off a 65 352, and a 4 speed. Its just been finished and when I cruise it will not run at a steady rpm. No matter how hard you try to keep it steady it does a very slight change in RPM ( no tach yet ). I guess you could call it surging. Its not bad but, I don't like it doing anything strange. I advanced the timing and it got a little better. I am not sure how to tell if its running to lean. I don't want a meltdown. I haven't really gotten into it yet, but it will break the tires loose easily and doesn't seem to stumble when you accelerate. Any ideas will be appreciated.