Holley issue

'63GT said

Yes, it could be checked cold...
But if its doing that over night, the float is too high. (cold back-fires is chokes system is too lean)

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I`ve checked the level hot and cold, running and not, seems to me fuel would run out of level port if float was too high? It does not.
Interesting that a cold backfire from being too lean, I`ll experiment with that.

Thanks for the tips fellas, I`ll update with results