Hey I was wondering if anyone knew if I I had to boost reference my powervalve . I'm running a 2300 2 barrel holly. The Jets are stock. I'm thinking that if there is a vaccum in the powervalve at all times it would stay open anyways?. . By the way it's a draw threw set up on a stock 170. Thanks for any help. Cheers
Boost reference on a draw threw
- Thread starter shawnkat
- Start date
The power valve has a spring on it that holds it open, more fuel...Vacuum pulls it shut, less fuel...Low load little throttle =high vacuum= less fuel...High load open throttle = low vacuum= more fuel...But if carb is too small for the demand of the engine and turbo it can get sucked shut..or air cleaner is bad it will also make it worst.
You need to have a wide band tell you, or you are just guessing.
You need to have a wide band tell you, or you are just guessing.
With the Draw-Thru (sp) setup, high vacuum at the carb will keep PV closed at all throttle positions. Carb'd draw-thru turbo's typically have a way to get the Power Valve Circuit to OPEN when the Intake manifold transitions to positive boost pressure .
GM-BOP V6's and V8' turbo's used a specifically built Quadrajet that simply ran the PV vacuum circuit externally and used a proprietary vacuum switch mounted on the intake manifold to 'switch' the carbs PV circuit to open under boost.
I used a generic vacuum-dependent fuel line shutoff to 'switch' the Qjet's PV circuit on my Draw-Thru BOP setup.
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The 2300 bbl mentioned has the vacuum port for PV between the bores on bottom of carb base. All modern 2300's have a small ball popper valve there to prevent backfire blow-out of the PV. The vacuum chamber behind the PV can be sealed from the port and an external port drilled,tapped and added to circuit 'switched' by manifold boost pressure.
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A new option for Blow-thru forced induction is a proprietary Power Valve (Holley type) made to Open under Boost which basically operates backward from a normal PV. It stays closed until bost and is adjustable. This requires sealing the PV vacuum port and letting fuel bowl pressure (Boost) operate the PV. Seems like a good idea, I'm building a 2300 for the new PV option.
have fun
GM-BOP V6's and V8' turbo's used a specifically built Quadrajet that simply ran the PV vacuum circuit externally and used a proprietary vacuum switch mounted on the intake manifold to 'switch' the carbs PV circuit to open under boost.
I used a generic vacuum-dependent fuel line shutoff to 'switch' the Qjet's PV circuit on my Draw-Thru BOP setup.
. 
The 2300 bbl mentioned has the vacuum port for PV between the bores on bottom of carb base. All modern 2300's have a small ball popper valve there to prevent backfire blow-out of the PV. The vacuum chamber behind the PV can be sealed from the port and an external port drilled,tapped and added to circuit 'switched' by manifold boost pressure.
. 
. 
. 
A new option for Blow-thru forced induction is a proprietary Power Valve (Holley type) made to Open under Boost which basically operates backward from a normal PV. It stays closed until bost and is adjustable. This requires sealing the PV vacuum port and letting fuel bowl pressure (Boost) operate the PV. Seems like a good idea, I'm building a 2300 for the new PV option.
have fun