Crazyhorse

You ARE ahead of me. No flies on you.

turbo2256

Hope to go laptop with dual turbo 5.0 87 Grand Marquis this year. Then my two boats next season or two. Going to use Electromotive with coil packs. But as I usally work on other peoples stuff before mine I have three customer's motors to rebuild now.

Cord

Crazy-that's EXACTLY what I was going to say!

US1 Fountain

bopp, thanks for the input.

Does your formentioned process work with blower motors too? Where do you take the vaccum reading at, manifold or under carb?

BTW, mine runs great. I have no idea on how it is calibrated. I read the method in the book, yet see that many here only mention about jetting to WOT plug readings.
Jerry

formula31

After I get the WOT jets right, I always check the plugs again at the rpm right before the vacuum secondary opens. This seems to be a lean spot. Just in case anybody else is running vacuum secondarys.

Bruce

US1, your carburetor was done on an air flow bench using calculated airflow guesses based on engine components and my experience (Read Wild Ass Guess). We measure the liquid running through the carburetor at given airflow's, and smack the carburetor with a hammer to adjust the flow rate until the desired fuel air mixture is achieved. Since your's is a Dominator that was boost referenced, we also had to use a hand vacuum pump to simulate part throttle boost and non-boost conditions. Gasoline is not used during the wet flow process due to the explosion hazzard, but we have this special urine obtained from a llama which matches the specific gravity of gasoline. It doesn't smell to good but it flows through the carburetor great. Hopefully your getting the picture of how your hard earned money was spent.

BOB ONEIL

Well hell, I didn't realize that's all there was to it. I've got a cat that pisses on my bushes so I guess all I need to do is place a jar under the bush and start collecting that stuff. Would that work? Oh by the way, how many hits with the hammer? Sorry just couldn't resist.
I remember reading that too Jerry. I also remember an artical in Powerboat about the lean condition just before the secondaries open but, he (Teague)did not go into explanation on how to correcct it. Since then I read a Holley book which pretty much said what Bopp explained.
Now all we need is a general consciences on how to read spark plugs..... But that's a whole other Post!
Bob

tomcat

This is a great topic to start the New Year! Forgive me as I think out loud.

Cars cruise around on primaries only with very little load. We have all been told that boat engines cruise like a car pulling a trailer up a hill at 80 mph. But you still want to do this on primaries only. Obviously the primary jets (and venturis)in a boat must be bigger.

According to one Holley book the PVCRs add 25-40% more fuel. This amount of extra fuel sort of corresponds with the size of jets and PVCRs. Say the primary jets are 80s and the PVCRs are .060. With the extra restriction of the power valve installation, the PVCRs maybe flow like .040 holes, which would be 25% more area. Is this enough for WOT? I guess not, since it is typical to have much richer jets in the secondaries.

In this case,opening the secondaries not only allows more air but richens the overall mixture. Presumably this extra fuel mixes with the leaner mixture from the primaries and results in an overall richer mixture to the cylinders. Since most carbs are set up this way, it seems like this works, but you wonder if the extra rich secondary jetting results in richer mixtures to some cylinders?

PVCR enlargement is a way of bringing more of the overall WOT fuel in through the primary side without increasing primary jet size and cruising fuel consumption. It may also even out the fuel distribution?

So I can see sizing the primary jets for cruising with power valves closed, and sizing the secondary jets for WOT with power valves open. Since the secondaries should be closed at cruise, I gather we are not talking about drilling them. So are we talking about drilling the primary PVCRs, and then reducing the secondary jets?

Now what about the lean condition at the top of the prmaries? Drilling the PVCRs makes them richer when the power valves open, but the leanout is due more to the timing of the power valve isn't it?

This condition sounds a lot like the reason Holley developed a two stage power valve for motorhomes. It added a little extra fuel at about 11" and opened fully at about 6". Holley does not recommend these valves for "High Performance" applications since the construction of the power valve reduces its overall fuel flow capacity. I'm not happy with this dead end; somebody needs to try this, it's easier than drilling PVCRs.

The other way of tackling this problem is to change the linkage so that the secondaries are cracked open sooner, a "soft, progressive" opening. This is the new linkage on the HP marine carbs recommended by Teague, I think as the solution to leanout at the top of the primaries with the old linkage, which delayed the secondary opening.

Final question: Holley sells "marine" carburetors. Do these carbs meter fuel differently to address any of this issues, or are they just USCG approved?

Bruce, if you're still here, could you check out my topic on blowthrough carbs. Would a two stage or modulating power valve, combined with much larger PVCRs, get us away from the problems of obscenely rich jetting being used on Prochargers and other centrifugal carb kits?

formula31

"The other way of tackling this problem is to change the linkage so that the secondaries are cracked open sooner, a "soft, progressive" opening. This is the new linkage on the HP marine carbs recommended by Teague, I think as the solution to leanout at the top of the primaries with the old linkage, which delayed the secondary opening."

And that exactly what I do to my vacuum secondarys, weaker springs so they open a little earlier.

boot

My dominators secondarys open almost right away ! I guess I don't have to worry about that lean spot at cruise!