36mm or 40mm

[phunkynova]

I now have two options which is best.

I have a 38mm inlet manifold for bike carbs but only have 36mm choke size carbs or 40mm choke size carbs which would be the best to use on the rally car ?.

I know 38mm to 38mm is the best but I do not have this option just now.

[therealnovaboy]

It depends on the diameter of the outlet of the carb. Ideally you want the carb outlet ID and inlet ID to be the same size or the ID of the carb smaller and the inlet bigger.

38mm would probably be best to keep the air speed up. it also depends on wheather you have port matched the head.

Are they the same length?