1 more 2 barrel carb question

[redman09]

there is a pin inside the carb that looks like a nail with a spring on it that sits on top of the jet under the float, can someone please explain its function and is it suppose to move up and down or not and if it wasnt would it cause the carb to flood?

 

[stonyloam]

Re: 1 more 2 barrel carb question

I don't know either, but Don does: http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/what-carb-337770.html

 

[achris]

Re: 1 more 2 barrel carb question

Sounds like the power valve. When the manifold vacuum drops below a preset level (greater demand for power) that 'nail' moves up and allows more fuel into the engine.

Chris........

 

[makonnen]

Re: 1 more 2 barrel carb question

Power valve.

It gets manifold vacuum that pulls it down against spring pressure. As you open the throttle, manifold pressure increases / man. vacuum decreases, the spring pushes the needle out of the jet seat and allows more air-fuel (the fuel port is vented to air) into the venturis thereby enriching the mixture. At idle, or when you drop the throttle back to idle, you have a low manifold pressure / high man. vacuum situation, the vacuum overcomes spring tensions and pulls the needle into the seat thereby blocking fuel / air flow.

These springs are usually color coded. Hotrodders will have a collection of colored springs to fine tune the power curve.