I got my old 52 f1 running and it has low power. Seems to vibrate like the new 8's that run on 4 to save fuel. Doesn't backfire. But sluggish.

 

I think you'll find that 2 on each side are dead. This is because one circuit in the carb is clogged. At least that was it when mine started running on 4.

 

I have 4 wet plugs and 4 dry. Changed plugs, wires and cap. No change.

 

See if they are front and rear cyls on one side and 2 middle ones on the other side. The wet plugs were getting fuel, the dry ones, not. I kept thinking ignition at first, but it was carburetion. Follow the runners in your intake manifold. They tell the story.

 

We will take a look. Thanks.