Yet another comparison (air-gap carb spacers)

I have tried spacers on dozens of engines. SOme with success some with no gain at all. I remember one 505 I built a long time ago, I tried 5 different types of spacers. We saw no real gain. All they did was lean out the engine about 1-2 jet sizes. I had another 416 that gained 25HP with a 1/4 4 hole merge spacer. But lost 10HP with a 2" open.

All I can say is TEST TEST TEST. There is no "This spacer always makes power" its BS. SOme combos like them, some dont.