help...jetting Holly 830 CFM annular carbs
 

help...running holly 5 1/2 lb electric fuel pumps in 502TRS Gen VI twins w/comp cams roller cams making about 500 hp in 86 Formula F302 with world products rectangular iron heads with big valves, MSD ignitions and stock intake manifolds.The carbs (performance series annular discharge) came with #85 jets all around.Using last years stock merc centerriser cast manifolds last year I ended up with #91 jets in primarys and #83 in secondarys and just running a little rich on rear 4 cylinders.I just switched to revolution marine exhausts and havnt run it yet, but found the rear 4 cylinders running REALLY rich while putting in new plugs.Is this a problem with float adjustment, the floor angle of the intake, or improper jetting? I also get a strong smell of gas after running awhile then sitting still about an hour..don't know if its a leaky fuel tank or not YET, but could it be fuel overflowing from improperly set float dripping into hot intake manifold when engine heat rises and evaporating after sitting still awhile? Its real strong the next day when I uncover it...but not noticible while running or when you first dock up....If floats...whats the correct method of float adjustment for this setup? While running?Pumps are wired in thru oil pressure switch for ground and key for pos..

Hardly ever do I end up with more than 2 jet sizes change in a performance carb. The primary sounds way too rich and the secondary too lean. They should all be within 2 sizes of each other. It sounds like you have float or power valve problems or something. pm or post more info and we will try to help!!

I'm running 83's front and 90's in the back on my 454's....still a little rich.

There are just too many variables for anyone here to give you advise as to jet size. You need to start with setting your floats correctly. As far as jetting, you need to do plug checks. Don't forget about the power valve.

At one time I had Holley HP-830's with annular discharge on each of my 540's that made 630hp @5400rpm. I was using #86 jets on all four corners and it still seemed to run a little on the rich side!

Ok...I got it running yesterday and still only got 4800 rpm out of it at 69 mph. Brought it back into the marina and pulled off the flame arresters. The port carb was all wet on top of the butterflys with gas. I pulled both carbs off and found the intake manifold on the port side puddled with raw gas in the little valleys in the casting so I mopped it up with rags before leaving and covered up the intake holes with rags. I'm going out shortly to see if there is a smell of gas in the bilge to eliminate a leaky fuel tank as the problem. If no smell...my problem would obviously be from heat rising up after shut down and expanding the gas from the bowls into the intake. I checked the float level of rear bowls of both carbs after pulling them off and they were right on the money...gas level right at the bottom of the screw hole. I'm gonna check the new plugs too in that I ran it for about 1/2 hour with new rear jets of #79. Please feel free to keep sending me any suggestions.....thanks... Glenn

pulled the plugs today...front 4 cylinders looked like no color at all....back 4 were all blackened out. What am I missing here? It almost looks like no matter what I do fuel is just pooling up in intake manifold and running to the rear. Am running Holly red marine fuel pumps without regulators. Someone else told me that you have to remove the fuel bowls to adjust the floats. Is this correct?

You do not have to remove the bowls to adjust the fuel level.
Look for heat discoloration on the ground electrode-should be near the end of the bend on the ground electrtode(near the end, not the case of the plug). The power valve could be a problem or about 10,000 other things. pm if you like and I will call you or try to help any way I can.

We're not talking a little bit of discoloration here.....I'm talkin the entire plug turning black and carboned up like painted with black spray paint after about 20 minutes of hard running on new plugs. I'lm guessing its a float problem on both motors.....but on the rear 4 cylinders of each motor. Am I correct in guessing its the rear float (stock 502 dual plane manifolds) or is it from raw fuel running down towards the rear of the manifold from the front flots due to the drastic downward angle of the motors in an 86 Formula? The floats are currently set with the fuel level just below the screw hole while the engines are running. I'm assuming the holly 4150's w/830 annular discharges are blowout proof power valves since they are only a year old....I've had plenty of backfires before zeroing in my timing and swithching to MSD ignigtions, and numerous restarts with no chokes. Any help would be greatly appreciated. Will be back in town with email access again satuday night leaving the in laws place after tonight. thanks much blown 1500 or anybody else with suggestions.......PLEASE help.....Glenn

What is the model # on you carb??
The one I bought three years ago did not have power valve protection. I added it and have never had a problem tuning the carb.
My guess is you have blown out the power valves.

It sounds like you are having a fuel pressure problem with both your motors. I also had the same problem this year and converted back to mechanical fuel pumps that mercury uses on the HP500's. Electric feul pumps have a tendency to push fuel opposed to pulling fuel from the tank like we all think. Install mechanical guages at your carborators and watch your fuel pressures at various speeds, and you usually will see a fluctuation in your pressure. Keith Eckert and Bobby Saccenti helped me solve my problem with my Apache. Please feel free to call me. Little Tommy 1-414-349-8567

the model number is 4150 Hp series. The numbers stamped to the right of those is 80558 and below that is 1689. Is there any other way to tell if I have the blow out proof power valves? I've got pressure gauges on the carbs right at the carbs.

I bought my Holley HP 830 carbs in January of 2001 and they DID have the blow out power valve protection which I was happy about because mine had backfired a few times.

I found the paperwork....I bought them in early 1999....Glenn

Just had a conversation with the guy that put my motors together....he said I should have a minimum of 8.5 power valve with the cams he put in them....he said they might even need a 10.5. I just checked the existing valves in the carbs and they are only 6.5 dunno if thats gonna do the fix or not

You must be running very high vac. at idle. The power valve should be about 1 1/2 to 2 less than your manifold vacuum at idle now.

I think he's going in the wrong direction but, I learn somthing new every day.:-)

Ask him what the vacuum gage reads.

Bob

I'll find out tomorrow. Picked up a vacuum gauge, am putting distributors back in with new composite gears, and carbs back on with jets squared at 86 and 8.5 power valves. Will be checking vacuum thru manifold .....not carb pull off tube. I'm just hoping to solve the problem of the puddling of fuel in the manifolds...I'm sure everything else will fall together if I can at least accomplish that. Thanks for the figure on the recommended numerical relationship of power valve number to Hg....this should be interesting. At least the weather is gonna hold up...(Lake St Clair...Michigan)

Hey Little Tommy...thanks for the offer of assistance. I did'nt wanna bug you till after I make these changes and see which way things go....I'm saving you for the last page of this chronicle in case I need you. I'll watch the pressure gauges closer tomorrow....but as I recall they stayed pretty steady....thanks

Your power valves are opening too soon. You should drop down to 6.5 or 4.5. What is your vacuum reading at 2000rpm?

Sorry, I just reread your post. I thought you had 8.5's in there already. I would still try 4.5 power valves. Boats under even a small load do not pull much vacuum.

While were on the subject of Holley Power valves WHAT IS the best way to test and figure out which power valves to use. Im running 2 of them.

BH:

Bad habit, my experience is with big blocks. You want your power valves to open when there is a fairly large load on the engine. A power valve is equal to about 6 jet sizes. On a carb that meters well like the 830, wait till later to add extra fuel.Use 4.5 power valves. With a 850 you would want to add fuel earlier. Use 6.5's or 8.5's. Some people block off the secondary power valve and add the jet sizes. Starting with 86 jets all around and 4.5's seems about right. If your engine isn't close at that point, there must be something else wrong.

Blown- Lean or rich, which way does the discolor move, in for rich, out for lean?


Formula- After reading all of this thread looks like you are headed somewhat in correct direction. I am guessing the 830 has a rear power valve. If so that is why you are way rick & the leaking into the manifold. If the diaphragm is blown on the power valve it will cause fuel from the bowl to leak to the backside of the power valve thus leaking thru hole in bottom of carb into manifold. As to what size of power valves to use we will need to know what your vacuum is in & out of gear at idle. In jetting a carb what you want to do is get the carb jetted for all of your throttle settings. First is idle, second is low speed, low rpm. As you increase the load on your engine you will want the power valve to open but not too early to supply more fuel for the additional load. My take on jetting is to first find out what throttle position the secondaries start to open. Mark this position. Then start & get the jetting correct for low RPM's first, once you have low RPM jetting correct then increase the RPM & check jetting there. Get primary jetting correct before you even open secondaries. Remember the power valve will open when the intake vacuum falls to the number of valve you install & will add about 6-7 jet sizes of extra fuel to engine. Once you have primary then start on secondaries. The trick to jetting is getting the jetting correct for all throttle settings, not just full throttle.

OK...I started that project friday and can't get the damn plugs outa the intake manifold to put the vac gauge on....they're the hex shaped ones in stock mercruiser intakes. Any suggestions?

Last time I had that problem I stripped the threads out of the manifold. Ended up removing manifold. I was told hindsight that I should have taken a propane torch & heated the area up & that would of caused it to break loose. Before you try that I would verify that this works & exactly how to do it. I am not sure where this plug is at but if plug is in an intake runner it will make your gauge pulsate.

Turbojack,

Can a vacume gauge be connected to the carb in any way for a correct reading?

By the way, when I had the 830's on my 540's I had the stock sized power valves that came with the carb when new---whatever size it may have been.

Kaama-Not sure. I will go out in garage & see if I still have one lying around & check.

Yea, the plug is on the intake runner just to the rear of the carb bowls. I've been told that trying to get a reading off a vacuum pull off on the carb is not accurate....but these carbs dont have a vacuum pull off tube on them anyhow so the only option I have is to go to the plug on the intake manifold. I'd assume thats the right place to go to...simply because there is NO other place to go!

So then what if a guy doesn't have a plug or provision for a vacuum tube in the intake? So really what is being said here is there is absolutely no other way to get a vacuum reading??? Drill & tap is the next option then?

Yea....thats about the way I see it...I'd sure hate to have to pull off the manifold and go thru all that crap just to be able to get a vacuum reading. Maybe I'll try that heat thing and use propane or MAPP...sure hate to ruin that nice imron I put on the manifold though....

OK...got out despite the rain today and found all four rear cylinders on both engines are still making the plugs run solid black. Still showing no color on front 4 cylinders. Switching to the 8.5 power valves from the 6.5 that came with the carbs did not clean anything up so I switched all of them back to the 6.5 power valves. Vacuum guage from summit has not yet arrived, and the hex plug on intake of one of the engines still will not come out. Can I go down to 4.5 power valves on the primaries to try to get fuel to the front 4 cylinders and leave the 6.5 on the secondaries, or even switch them up to 8.5 to lean out the secondaries? I'm still running #86 jets on all four corners of the carbs.

If you have a carb spacer, you could drill and tap it. If not, installing a carb space would be a lot easier than taking your intake off.

If you are using the old power valves throw them away & get new ones. I would say use 4.5 all the way around. Of course we will not know until we find out what vacuums the motor has at idle & under loads at different RPM's. Is the guy that rebuilt your motors a car guy or a boat guy? I have found that alot of the car guys do not understand the loads that boats put on motors & will give you all kinds of incorrect info. I am assuming you have adjusted floats already, just below the sight opening?

f302, you have the concept backwards. 8.5's are in effect richer than 4.5's because they open sooner. The number on the power valve refers to the atmospheric pressure in inches of mercury when they open. 4.5 is a good number for boats.

Change your oil if you are puddling that much fuel!

However,I don't think changing from a 6.5 to a 4.5 will make that much of a difference. Something else is still wrong.

OK...my engine guy is a car guy I must admit....however I think I've just stumbled on the problem....I'm using a square bore 4150 carb on a quadrajet alum mercruiser intake designed for a spread bore but with both bolt patterns for the studs. I have a summit linkage plate below the carbs with a square bore pattern on it and it hid the ridiculously different pattern of the spread bore intake from my view. It looks like lots of dead zones for velocity and fuel atomization below this combination. I did'nt know there was an adapter plate available or necessary for this....but I ordered two new sportsman II intakes from merlin today that are designed for the 4150 carbs. I've heard pros and cons about the adapter plates..so I took the easy way out and went for the new intakes at $215 each from Bill Mitchell Hardcore. Unfortunately by the time they get here, I paint them, and return from a quick vacation I won't be able to post the results till about 2 weeks from now...but I'm anticipating a huge positive difference. If its not....I'll sure be back on my hands and knees begging for more advice. Thanks to everyone...having that many people telling me that something is severely wrong caused me to did deeper for a problem instead of just playing with just more fine tuning float and jet adjustments etc. I'm just hoping the intakes correct it.....don't be afraid to tell me if I'm on the right or wrong track. Thanks again to all... Glenn

BINGO anyone! Back to square one.