Ted, he has something going on that is different from one side of the motor to the other (or that's my take on it) It started suddenly and is there all the time.
As you would know, a problem in the carb (after the float chamber) effects two cylinders each side)
Wmg, O.K. now while nothing else is changed, take the four spark plugs from the side that noticeably drops, and swap them into the other side. If all four on the side that dropped off before, all do the same with the other plugs in, that will tell me that the plus are all ok (just because they are new, doesn't mean they work)
You should be able to tell if its firing on all cylinders when you short out each individual plug, so we need to know is it running on seven or eight, (or four?)
If the same four are still not showing a noticeable drop, then some thing funny is going on (intake manifold gasket, head gasket, blocked exhaust on one side)
You can get cross firing, which happens because the spark leaks from one lead into another, which makes the wrong cylinder fire at the wrong time.
If you are getting this, there is a good chance she is back firing up through the carb, or popping at the exhaust. This however doesn't fit with four cylinders in one bank performing the same.
To give you a reasonable diagnosis, we need an accurate description of the problem.
See how you go.
