I am hoping this is a general question, because I am going to treat it as such.

The idea behind the power valve is that when the vacuum level drops, it effectively makes the main jetting much larger. Having "too high" of a power valve size allows the fuel level to increase at much too high of a vacuum level. By reducing it (numerically) you are holding the enrichment out to a higher throttle setting (lower vacuum level) and effectively increasing the fueling when the jet starts to really pull some HP...

I am seriously hoping that helps clarify, if nothing else, at least causes more questions.

In all honesty, I would rather see the PV's eliminated and different jetting on a dual carburetor set up, it just makes tuning that much simpler. Maybe just me.

GT

Thanks GT, I don't think I could have explained it that well.

The other problem, and probably the main reason to lower the power valve starting point is due to the reduced vacuum caused by large cam profiles causing the PV's to blubber or start adding fuel at idle.

So are you saying that the power valves are kinda rattling around causing the idle issue?

Like I say it's really close but I have noticed it kinda takes it a while for it to settle down sometimes close to idle.

It's on and off throttle great but it kinda acts like downshifting a manual shift car when you let out of it close to idle.

I don't mean like downshifting at 4000 rpm, it's like about 1500 rpms to 800 rpms.

 It kinda wants to hang up for a second or two before it settles back down to idle. Not every time though.

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Do you know what makes a power valve work?

Not being a snotbag, just curious.

If at a slower idle you are only making 6 or 7 inches of vacuum,  the power valve will be on the edge of open, which is like jumping three or four jet sizes in a matter of seconds.. I am starting to think this is the issue....

GT

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Guys, as I said in the beginning,  I own a carpet cleaning company. I have never and will never claim to be a mechanic. That is why I come here, a forum full of mostly knowledge. I am doing the best I can and would say I have come pretty far from where I started. If you research out my history here I came here with a hull and a pump which I just rebuilt myself also.
No I do not know the complete purpose of a power valve but I have an idea. Maybe rattling around was not the right phrase but we'll say low on vacuum enough to let it leak.

I have gotten a lot of useful info from alot of people here and I appreciate all the info and help I have recieved, especially the ones who have taken time with going the extra mile and using private messages to explain so I can understand.
Anyone need advice on carpet stains or repairs, feel free to ask. I do have 20 years exp. With that.

Sent from my SAMSUNG-SGH-I337 using SoCal Jet Boats mobile app

Well now you're making me feel bad... I was not criticizing, not even a little bit. I was just trying to put information out there for you and potentially anybody reading this thread, how this circuitry works.

I was not calling you out, which is why I asked a question, then followed it up with an explanation.

I apologize if you read it that way.

Moving forward, I would not recommend trying to adjust it any more without a vacuum gauge hooked to base plate (or manifold) vacuum. I believe you are fighting a power valve issue.

Pick up some 4.5" power valves and some metering block and bowl gaskets. Don't forget to coat them with Vaseline before putting the carburetor back together....

And lose the PCV. If you need a reason, because I said so.   

But seriously, you are making too much crankcase pressure for a PCV to even do anything. A PCV is a SMOG device and doing you no good at all....

JMHO..

BTW, my goal is not to make everybody a mechanic, but to provide input based on your questions...

If at any time you feel disrespected by comments made here, not just from me, but anybody, speak up. That is one thing that makes this site different... In a good way. 

GT

The reason it ran like shit with the mechanical conversion is because you've got no pump on the secondaries...can't slam 'em open like the primaries.

Power valves should be OK...even 6.5s.  Unless you've got a stupid lumpy cam in it, you're making much more vacuum than that at idle....probably over 10". 

Power valves are held closed until vacuum drops below the rated level of the valve you're using.  They make tuning a bit more tricky, and since in a boat, you never really have low load conditions, they're mostly open unless you're idling.  Like GT said, I'd plug the power valves and jet it up about 6-8 sizes.

At idle, the blades need to be closed enough to cover the transition slots.  It needs to idle
On the idle circuit.  Sometimes with stupid big lumpy cams, you can't move enough air without introducing a leak while keeping the throttle angle out of the transition circuit....that's when we drill holes in the blades or in a pinch, make a small vacuum leak and fatten up the idle fuel to compensate.