1978 Mini 1000. Head is off at the moment - burned an exhaust valve
While I wait for tools / parts I examined my carb / inlet setup.
Carb is an HS4, K&N conical filter with a small stub stack installed. There is a spacer between the carb and the inlet manifold which is a Minisport alloy unit to which either HS4 or HS6 carbs can be installed (1.75 inch opening).
In looking carefully at the parts I came across a couple of things that I would like to understand better, I am not looking to replace any of the parts at this time just figuring out if I need to modify or remove them
(1) The stub stack inside the K&N filter has a slightly narrower ID (~ 1/16th) than the inlet for the HS4 creating a small step for air entering the carb. Should I remove some material from the stub stack, leave the step as is, or just remove the stub stack.
(2) The throat ID leaving the HS4 is 1.5 inches but a chamfer has been added (not sure if this is stock or not) adding another 1/16th to the ID. The spacer is 1.5 ID so again, there is a step. Should I remove some material from the spacer to match or leave it alone.
(3) Finally, the inlet ID to the manifold is 1.75 inches which I understand means you can mount either an HS4 or an HS6 to this manifold. But this makes a pretty big step for the air leaving the HS4 carb and entering the manifold - is this okay or should I consider tapering the ID of the spacer to "blend" the air flow into the manifold.
Thoughts / Comments appreciated.