To have the throttle blades open too much due to a lean carb idle circuit/vacuum leak is a guarantee for dieseling.
A hot cam acts just like a vacuumleak and a vacuumleak causes a weak signal through the venturi in carb.
A weak signal through the venturi isnīt able to pull enough fuel from the idle circuit, so the idle circuit needs to be opened to correct dimensions for the present vacuum.
With ignition properly set and carb mixture adequat for the setup the throttle blades will be in the correct position at idle.
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