The perfect way of jetting a Holley
 

Full of questions tonight! ;)

How many of you guys determine your jet sizes by reading the plugs at WOT?

According to the motor Bible(Dennis Moores BBC Marine Book), you are supposed to jet you carb at CRUISE, at which point you have 100% flow thru the jets.
And you control the WOT mixture by drilling the power valve metering holes larger if more fuel is needed at WOT, when the PV is open. Page 159-160. This gives the best A/F mixture and economy at cruise, and still having the needed A/F mixture at WOT. By jetting only at WOT, you may have a poor cruise mixture,= poor economy.
I'd be very interested if someone else would read that article and post their thoughts.
Jerry

if it pops, it's lean.. if it blubbers, it's rich. :D

I never run below WOT. And I set my jets there. My secondary power valve opens as soon as the secondarys do. What I would call cruise speed would be arounf 4000rpm and my secondarys havent opened yet. I suppose the size of the boat and load on the engine would have some bearing on that. I read the Holly high performance book. Interesting question though, have to look at that a little more closely this spring.

Ok it goes some thing like this set your jetting to your highest cruse speed power valves closed or blocked off use a vacuum gage to deturmin full cruse vacuum. then put a power valve in that wont open untill a less vacuum is reached about one or two inches lower if your reading is 7 go with a 5 or a 6. Now you guys with more radical cams need to check idle vacuum to se if the vacuum drops below the reading found at your cruse speed or the power valve circut will open at idle causing a rich condition. So in this case a power valve of a lesser value must be used than the idle reading. If it idles at 4 you might need a 3 or 2.5. Ok back to top end. Run it up to top speed kill the engine at that point dont idle down read the plugs. If they show lean jet up... rich jet up. What ever it needs untill it runs and reads right. Now its runing good there her comes the fun. If you had to richin it up in a holley chart find the flow data for the jet ( cross section area) find the differance between the best top speed jets and best cruse jeting. Measure the power valve feed restriction dia. Figure its area and add to it the differance found in your high speed and cruse jeting find the drill dia that will give you the hole dia needed to accomplish this. REMBER YOU ARE WORKING WITH AREAS AND RESULTING HOLE SIZES NOT DRILL SIZES OR YOU WILL GET THINGS ALL SCREWED (<<< BEING NICE HERE) UP. If you need smaller get a bushing to fill in the hole and drill it to size or JB weld it and drill or may be a small lead weight out of the fishing tackle box tapped in the hole and drill. Before you start this process aquire HP book on holley carbs and Peterson READ AND STUDY THEM BEFORE STARTING THIS. WHAT EVER ELSE YOU DO YOUR BETTER A BIT RICH THAN LEAN. Mabe a good pro mechanic might be more help.

bopp,
Good explaintion! Welcome to the board!
You need to balance the jets with the PV orfice to get what you want at any rpm range. You can do the same thing with EFI, except you use the lap top instead of drill... :D :D :D
Sorry just couldnt resist. Been there done that sort of thing. The best advice is to read that book several times. Then go slowly at any changes..

The key thing when you are doing this type of tuning would be:
1) make sure you have enough fuel at WOT
2) double check your vacuum at idle to make sure the PV is closed at idle (so that your engine will idle cleanly)
3) make sure you check the amount of vacuum your engine produces at your cruise speed this will determine if you PV is closed at this speed and this type of tuning will help you
4) before getting into any type of calibration changes in a carburetors metering circuit make sure it is performing properly. Doing this to cover up another problem will not help
5) make sure the idle circuits on your carburetor are set up and working right before doing anything else. If an engine doesn't idle clean, you can't expect it to do anything else correctly. Make sure that your butterfly's are positioned properly before you start.

Damn i really love my EFI now :D :D

And it gets worse. Now figure out how to do that with twins when you cant even get at the center plugs, and unless youre real high out of the water or running dry pipes, the engine will hydrolock when you shut it off at wot. Been there, done that.

The perfect way to jet your Holleys is to send Bruce a round-trip plane ticket and buy a box of jets. :D

Crazyhorse, I'm 2 steps ahead of you. Already have the Holley jet pack, AND had Bruce work over my carb this summer. :D Do to funds, only the carb made the round trip. ;)

You ARE ahead of me. No flies on you. :D :D

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.

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

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

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.

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. ;)

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

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?

"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.

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

Bruce, Don't get me wrong, I'm not questioning my carb that you did. Like I've said before, it works Grrreeaatt! (Tony the Tiger impression :D ) I'm just bringing this topic up because of the way many seem to jet theirs. I guess if they run WOT 100% of the time, it'll work fine.
You know, before I sent my carb to you, I have many many times thought of taking a hammer to it myself. Just didn't realize how close I was to doing it correctly, minus the key ingredent, Llama pee! :D
So, will you also use that hammer method to seat the valves on my heads? ;)
Jerry

Dont use cat pee. Its to corrosive. Just look at what it does to the rims on your car.
Take the reading under the carb not from the manifold. The hose keeps blowing off.

Tomcat, looks like you've been reading the same stuff I have. I like the two stage power valve theory but, I wounder if they discontinued it because it did not work consistantly?
The other thing is in Teagues artical I think (if I remember right)he stated that both the #9381 (non-marine and non-HP with choke tower) and the 80558 (which is marine and HP)both had soft secondaries but, if you look at any Holley literature they don't mention it. I know these are similar to the 80509 and 80511 which both state that they are. Do you are anyone know for a fact if they are or not? Thanks.
BTW Bopp, I figured I would not be able to use that after I seen what it did to my bushes! :D
Bob

Holley also discontinued the electronic fuel bowl that allowed the driver to change jetting on the fly. I remember these products being advertised, but have no experience with them. They were called the Mile-a-Dial and the Quarter Mile Dial. OSO member "bck" was looking into this for blowthrough carb application.

US1, I was just trying to explain why I had to charge so much money for your custom carburetor work, it's complicated stuff. Your on the right track with your research on jetting. Tomcat, I did follow your thread on blow through carburetor's, I must admit it caused me to drink heavily and brought back many bad memories of poorly performing engines, blown head gaskets, and burnt pistons. My conclusion is that carburetors cannot deal with the density of pressurized fuel/air, they signal totally on velocity. I install take-off EFI manifold / fuel system's on any engines that get Procharger's now. I will not do a blow through application any more. I wish you all the luck, somebody has to come up with a working solution it might as well be you. If you need a EFI set-up for your engine I have four in stock. :D

Blow through and EFI is really the only way

Thanks for the advice, guys. It's true, I don't really need the aggravation of solving the fundamental problem of pressurizing a carb. But there are a lot of blowthrough systems out there that could use a better carb tuning device/service. The issue is cost. If an EFI system to go with my Procharger costs say $3000, then would $1000 to modify my good marine carb be a deal? Only if it works...I'll keep you posted if I find a way! ;)

tomcat, look in the classifieds. Someone selling a full EFI setup for $1500 if I remember right.

Whoa... I thought I knew a little about Carb's... but you guys on this board have really taught me a thing or two.... I knew about the hammer... but never heard of the Llama urine... great stuff... personally I prefer Demon carbs... they are very adjustable 7 user friendly....

Actually I will never purchase a Holley carb againatleast new. Therecasting equipment is to old. Bought a750marine carbfrom them lst year good thing I took it appart befo runing it. Casting flash all over out side of it all down in venturies boosters, accelerater holes between the bowel and meteing block, throttle plate holes are smaller than the bottom of the ventures and missaligned with them, metal filings inthe carb. Sent it back to the factory,theylost the carb monts late I got it back with two different style floats fix all but the missmach between the throttle plate and the carb body. Ran it that way but sometime when my friends vertical mill is free I will have to machine the bottom of the carb body down so it matches the throttle plate. Had to remove the roll pins to align the body to the throttle plate better. Should have made my own carb.

bopp - That's disgusting QC. I've got one better. I bought two new HP 830 marine carbs for my 502s. Breaking in the engines on the dyno they wouldn't run worth a you know what. Holley said jet them up, jet them down, didn't help. Couldn't be the brand new carbs were defective could it?! Switched to the old faithful dyno carb 750 and picked up 50 HP. When I sent the fuel flow figures to Holley they admitted that both carbs must be defective!! This BS and searching for every other possibility other than the new carbs cost me a day of dyno time. I sent them back to the supplier and ordered #9022 800s, the regular marine carb. They worked fine.

yea Ive seen some real junk from holley lately, thats why I love my old late 60's 3310's. They were built for GM's 450 hp corvette's