When running a carb with a turbo. Is there boost pressure drop like there would be with an intercooler; psi drop happening in manifold ? If I set my waste gate to purge at ten psi, would my engine act as if it is only receiving 8 psi ?

 

Yes, there is some pressure drop, depends on the carb. The bigger the carb the less pressure drop there is.

 

Yes. Carbs work off pressure drop. Without it , they dont work.

I reference wastegate signal off the intake manifold for this reason. If I aim for 10 psi, I usually get 10 psi this way.
If wastegate is referenced of compressor housing or hat, the boost the motor gets will be lower.

 

What worry about the boost. It really depends on the engine design and detonation as well as how free flowing the exhaust is.

 

Well. Carbs work off venturi effect, they produce their own pressure drop in a venturi.
https://en.wikipedia.org/wiki/Venturi_effect
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So, lets say the engine consumes 500CFM and we install a 600CFM carb. The atmospheric pressure is 14.5psi and the intake manifold pressure will be 14.49555psi - there will be no significant pressure drop for the intake manifold. The carb itself will produce a pressure drop inside a venturi to draw fuel into the air stream but this will not greatly influence the pressure of the intake manifold.


So now lets double the pressure using boost- 14.5psi + 14.5psi of boost. We have 14.5psi of intake manifold pressure because the CFM rate of the engine never changed and the CFM rate of the carb is sufficient to feed the engine volumetric rate. However the turbo must flow twice the CFM because it draws air from atmospheric pressure -> 1000CFM through the turbo at 14.5psi, 500CFM through the engine at 14.5*(2)psi, 500CFM through the carb. No pressure drop for the intake manifold due to the carb size being oversized exactly as in natural aspiration.

Atmospheric pressure can be treated exactly like boost pressure with respect to volumetric rate pressure drop. If you have a pressure drop at atmospheric pressure then you will have a pressure drop under boost. But an oversized carb will not create much pressure drop because just like a throttle body which is oversized, there won't be any restriction for the CFM (Volumetric rate).