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Hi guys. Is it really this easy??? I would like to get my Holleys boost referenced as I currently am PV plugged and jetted up accordingly but I would like to clean up the idle/low speed drivability.

http://www.fordmuscle.com/forums/in...ce-your-power-valve-supercharged-engines.html
Do your metering blocks have a ported vacuum port on the primary side? if so the last one i did i rerouted the power valves to use this Port. i have a tech Drawing saved on my computer i'll dig it up.

Edit: i forgot to mention that ported vaccum is not controlling the powervalve function, explanation below.
 

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Do your metering blocks have a ported vacuum port on the primary side? if so the last one i did i rerouted the power valves to use this Port. i have a tech Drawing saved on my computer i'll dig it up.
If its a blower motor, you definitely DO NOT want to do that. Port vacuum increases with air flow thru the carb, as in increased RPM. This how vacuum secondaries are opened. Internally the same port. Soooo, on a blower motor, the faster the engine runs and the more air flow thru the carb, the more vacuum, and the more the power valve will stay SHUT. Not a good thing! Yo0u have to take it to the intake manifold. Don't expect a huge gain. Mostly just off idle. Zero effect at idle. Just remember the second the intake manifold pressure (vacuum) gets above the valve setting, its open. And that comes sooner than most think.



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Damn, I new i wasn't posting fast enough and gn7 already jumped to conclusions:)hand

I didn't actually do mine this way, but it gives you a general idea of what your doing.




Instead I plugged the Power valve passage in the bottom of the main body that matches up with manifold vacuum, also plugged the ported vacuum hole in the bottom of the main body. You can use lead shot or little brass set screws. Then in the face of the main body i angle drilled the passage from the ported vacuum hole to to intersect the cavity the power valve sits in.

Or you can do it the way shown in the link you posted, i'm sure one way may be easier than the other depending on the components you have. and each will have the same end result. However if you use set screws the modification should be fairly reversible.
 

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So there is alittle more to it than just hooking the power valve port to the ported vac circuit:D Because without clarifiying that, it was a disaster lokking for a place to happen.:)hand
Yeah i know, there was a little lag time from the time i posted the teaser to the time it took me to formulate my response and upload the picture:)coffee more caffeine will help that.


Just realize it may have all been in vain because i think i remember that John has Proform main bodies. I know the way QFT does this is buy drilling straight through the side of the main body into the Power valve chamber. Just don't drill through the venturi. you still have to plug the passage on the bottom of the main body.
 

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why don't you just tune the powervalves instead of blocking them? i hooked up a vaccum gauge under my 750's on my blown 475, took it to cruise level while watching the gauge and my a/f meter, kept in mind the vaccum under the carb at cruise and i put the appropriate p/valve in so when i stepped into it above cruise, it'd enrichen with the p/valves opening. worked for me, had a nice clean a/f ratio and purdy plugs.
 

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why don't you just tune the powervalves instead of blocking them? i hooked up a vaccum gauge under my 750's on my blown 475, took it to cruise level while watching the gauge and my a/f meter, kept in mind the vaccum under the carb at cruise and i put the appropriate p/valve in so when i stepped into it above cruise, it'd enrichen with the p/valves opening. worked for me, had a nice clean a/f ratio and purdy plugs.
I believe he is trying to set it up so he can unblock them. He has PV plugs now. Don't know why your vacuum drops under you carbs when you floor it, but mine climbs, and I am running two 1050s. You would have to be running the blower pretty slow not to have a vacuum increase under the carbs when its WOT.



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why don't you just tune the powervalves instead of blocking them? i hooked up a vaccum gauge under my 750's on my blown 475, took it to cruise level while watching the gauge and my a/f meter, kept in mind the vaccum under the carb at cruise and i put the appropriate p/valve in so when i stepped into it above cruise, it'd enrichen with the p/valves opening. worked for me, had a nice clean a/f ratio and purdy plugs.
If you turn that blower up you'll see enough vac. at the carbs at wfo to close the powervalves & burn up one of your pretty little plugs:D
But of course , you already knew this , right?
 

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Discussion Starter #11
Thanks for all the replies guys. Just got off work.

Yup, blown bigblock. Josh is correct, I have 2 850s that have Proform mainbodies.

As I mentioned, I'm currently plugged and jetted up but would like to clean up my cruise ability and get some fuel mileage back compared to where I am now.

I've seen carbs where they're referenced off the metering blocks and I've also seen them referenced off the plate but have never actually read what all is required to reference them. After looking over the links it sure LOOKs easy (but, I've made that mistake before :)grn). Just not sure if it really is that easy and if folks have a preference of which approach is their favorite.

Definately don't want to risk putting them in without referencing and have them shut at the worst possible time and as Hass mentioned, burn a plug (;)).

Also, would the PV rating change when you swap pulleys? Go ahead and flame me, I can take it. :D

Thanks guys................john
 

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Thanks for all the replies guys. Just got off work.

Yup, blown bigblock. Josh is correct, I have 2 850s that have Proform mainbodies.

As I mentioned, I'm currently plugged and jetted up but would like to clean up my cruise ability and get some fuel mileage back compared to where I am now.

I've seen carbs where they're referenced off the metering blocks and I've also seen them referenced off the plate but have never actually read what all is required to reference them. After looking over the links it sure LOOKs easy (but, I've made that mistake before :)grn). Just not sure if it really is that easy and if folks have a preference of which approach is their favorite.

Definately don't want to risk putting them in without referencing and have them shut at the worst possible time and as Hass mentioned, burn a plug (;)).

Also, would the PV rating change when you swap pulleys? Go ahead and flame me, I can take it. :D

Thanks guys................john
I'd do which ever way you feel most comfortable with, the end result should be the same no mater which method you use. As far as tuning your power valve, your vacuum gauge is your friend.
 

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Thanks for all the replies guys. Just got off work.

Yup, blown bigblock. Josh is correct, I have 2 850s that have Proform mainbodies.

As I mentioned, I'm currently plugged and jetted up but would like to clean up my cruise ability and get some fuel mileage back compared to where I am now.

I've seen carbs where they're referenced off the metering blocks and I've also seen them referenced off the plate but have never actually read what all is required to reference them. After looking over the links it sure LOOKs easy (but, I've made that mistake before :)grn). Just not sure if it really is that easy and if folks have a preference of which approach is their favorite.

Definately don't want to risk putting them in without referencing and have them shut at the worst possible time and as Hass mentioned, burn a plug (;)).

Also, would the PV rating change when you swap pulleys? Go ahead and flame me, I can take it. :D

Thanks guys................john
It shouldnt. If you boost reference them to manifold vac.
 

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Thanks for all the replies guys. Just got off work.

Yup, blown bigblock. Josh is correct, I have 2 850s that have Proform mainbodies.

As I mentioned, I'm currently plugged and jetted up but would like to clean up my cruise ability and get some fuel mileage back compared to where I am now.

I've seen carbs where they're referenced off the metering blocks and I've also seen them referenced off the plate but have never actually read what all is required to reference them. After looking over the links it sure LOOKs easy (but, I've made that mistake before :)grn). Just not sure if it really is that easy and if folks have a preference of which approach is their favorite.

Definately don't want to risk putting them in without referencing and have them shut at the worst possible time and as Hass mentioned, burn a plug (;)).

Also, would the PV rating change when you swap pulleys? Go ahead and flame me, I can take it. :D

Thanks guys................john
We never flame people who ask straight up questionshil:)hil:)
It doesn't much matter the vacuum enter the carb. Thru a new channel in the plate, or thru a modified channel to the metering blocks. And yes it is pretty simple. All you are doing is stopping the PV from getting it vac signal from under the carb and feeding it a vac from the manifold. No, the pulley change has very little effect on jetting period. But I will warn you. If you think this is going to make some huge difference in the way the motor runs or its fuel consumption, your in for a let down. It has no effect on idle AT ALL! Most effective on off idle & slow cruise. Once the manifold pressure gets above the PV rating, its open. It doesn't have to be in boost, just less vacuum than the PVs rating. And that comes on sooner than most think. If you want to know when the PV is open or closed, tee in a vacuum gauge on the line. Suggest a 4.5 or 4.0 PV



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Discussion Starter #19
Many thanks to all of you for the information and advice (and not flaming me ;)) I'll give it a try.

Agree that it's not going to help a bunch with the idle but for things like cocktail cruising with the better half, it's bound to help.

Thanks again.

Yah, but I can still tell a better lie than that old bastard can.......:)grn See ya
 

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Many thanks to all of you for the information and advice (and not flaming me ;)) I'll give it a try.

Agree that it's not going to help a bunch with the idle but for things like cocktail cruising with the better half, it's bound to help.

Thanks again.

Yah, but I can still tell a better lie than that old bastard can.......:)grn See ya
OK you Old fart . I may not participate here but I do "lurk" and my Grand kids can whoop yours ! Hell yes I'll swap the pulleys guess I'll have to hual the Mach 1 up there and show ya "whats up" !! problem here is the damn lakes are dry ! motors got less than 60 seconds so far :)hand
 
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