Effect of headers on fuel mixture

[66FBCharger]

Does swapping exhaust manifolds for headers affect the mixture of the carb? I always thought that the headers tend to make the carb run lean so you need to jet a few sizes richer.

[Ghoste]

I don't know how many sizes on the jets, but they do tend to lean an engine out.

[Cooter]

In a word, it COULD. most times the carb straighten out due to being far too rich before header swap.

[Ghoste]

Unless its one of those emission calibrated ones.

[Dino]

So if the manifolds get swapped for headers then it should scavenge the gasses better thus (maybe) requiring a change in mixture right?  What if you change your exhaust for a much better flowing version but keep whatever was bolted to the engine?  Will you still need a tweak?  Not saying it's not wise to do that regardless, just trying to find out how this all works.  Sometimes I'm still flabbergasted that this huge chunk of iron is an air pump!

[Ghoste]

Depends on what was bolted to the engine.  If it was emission calibrated it was quite likely already to the lean side and then it could be an issue.  As Cooter said though, so many of these engines run too fat to start with, so...