Comanche3Six

Power Valves equal about 10 jet sizes richer when they open.
I go with the lower #2.5 because I don't want it to open in the slow speed no wake 5mph zones and foul the plugs or get the transom dirty. This comes in handy when running against a strong current and I need to use a little more throttle to maintain position. Some of these slow speed zones are long and tedious.
I like to run my Holley dominator with the power valves both in the primary and secondary metering blocks and the jets are all the same size with extensions on the secondaries. Be aware that there are standard power valves and high performance power valves available from Holley.
Good Luck
Ed

lloyd

I am jetting a carb that was built by Nickerson Performance. When I talked to them about power valve selection I was told to cruise at 3800 rpm, take a vacuum reading and that was the power valve to use. ie: 6.5 lbs vacuum use a 6.5 power valve. This is not a supercharged boat.

merlin540

caveman is dead on the money about the boost ref deal. i wont build a blower motor without it seeya

RLW

My former supercharged engine was not boost referenced and ran like a top. Idle and low speed driveability were excellent. Zero transom soot and spark plugs were perfect.
There is more than one way to setup a carb for a blown application and have great results.
Nickerson Performance 215-781-1370

KNOT-RIGHT

Yes I agree.

1)Deans way

2)Braswells Way

3) Holleys way

4)Barry Grants way

I'm sure theres more.

Removing the power valve and increasing the jets is how one would
eliminate the P/V. This really does eliminate a carburetor's circuit. If pv is removed most aftermarket carb gurus no exactly how to modify a carb to add appropriate fuel for the demand of the engine. Yet it still blankets the need for a PV. I have seen situations where P/V,s are questionable. See my own example above. So lets look at Blower calibration. Specific situations can be different.

Are the carbs mounted Tunnel ram style? Sideways?
Then tunnel ram floats should be installed They are
slashed in the appropriate ends so when they are mounted side ways
and the fuel flows to that side of the bowl it doesn't shut the needle
and seat. How about spring loaded needle and seats. Have you ever Smashed on rollers where your passengers are screaming at you and The boat not you
lays down? How about progressive 1-1 linkage.That will give even fuel distribution. Look down the carbs next time your leaning over a sideways mounted carb blower engine and wonder which cylinders would get fuel first if you were not running 1-1 linkage.Bigger Idle air bleeds to help the notorious blower surge. And lets not forget the metering blocks after all it has a little help getting the fuel and air through. Lets take a Roots style three lobe design. Guess what cylinders run lean?? Not the back like N/A. The front.The design of the twisted rotors in the blower feeds the rears first. So lets stagger the jets. Then we have the P/V to reference or not? well we all know theres all different opinions on this just do a search. Should we ask our selfs
why when we whack the throttles now it has a flat spot? Because we have a blower on the engine with a intercooler. and now the carbs are 15 inches higher above the heads. Bigger accelerator pump cures that.

Carbs in general are great when setup properly.
But it takes know how and patience and of course alot of Beer

If you really want to do it . Sell the carbs and do FI. Really the only way.

Just my 02.
Sorry for beating the hell out of this Horse.

RLW

Cave,
No need to be sorry. It's all good stuff!
Russ

BenPerfected

There are numerous variables as to when the PV opens. In your search for perfect, this is the proceedure that has worked for me. I start a little rich which is a larger PV like maybe a 6.5. Now take a 20-30 min. cruise at 3300 to 3500 RPM. If you have soot on the transom, keep dropping the PV one size until you are clean.
I like suggestion to run the boat with a vacuum gauge. This should get you close.

Wobble

This is great info, I have dyno time setup on my motor, however there really isn't a way to duplicate minimum planing speed mixture there. I had been told to drill the primary high speed air bleeds in 001" increments to lean out from 1200-3000 rpm. Before I get into that I will hook up vacuum guage and see what readings I get and swap primary powervalves accordingly.

Thanks,

Mark

BenPerfected

Mark,
It is my understanding that the Holley air bleeds are for very small adjustments. More for drag racers fine tuning. When the PV opens is an an instantaneous change equivalent to 8-10 jet sizes. If the PV opens to soon, you are in very rich condition.

Wobble

Ben,

I am certainly going for the power valves first hopefully this weekend. Let u know how it works out.

Thanks for your time.

Mark