Exhaust leak through carb????

Been busy doing my normal work since I'm on the clock. The springs are 509" lift singles that came on the heads from Indy. Haven't had time to do a leak test and probably won't. Appreciate everyone's input and ideas but after 44years every engine I've seen with no compression in neigboring cylinders always meant the same thing. Blew the gasket. And it always seems to be 3 and 5 or 4and 6. I've just never had, or noticed it ticking through the carb. Imagine it's the exhaust from one valve Coming up through the open intake valve on opposite cylinder