Couldn't agree more with GTX, he is dead on with a starting place on timing but assuming you have stock style outboard carbs and you think it's running lean, you can still adjust the fuel at the throttle bases. This is a pain if you have stock bases on both carbs (I run a promax base on the rear outboard) so I can adjust without taking it off the car. But it can be done, it's not a perfect way of doing it but if you adjust the front carb first, you can move it to the back then adjust the other. With the engine warmed up and at idle, put your finger over each air bleed on the outboards, if the engine picks up it's too lean, slows down then too much fuel.
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