help...jetting Holly 830 CFM annular carbs
06-05-2003, 01:19 PM
#22
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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.
06-05-2003, 05:19 PM
#23
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Originally posted by blown1500
Look for heat discoloration on the ground electrode-should be near the end of the bend on the ground electrode(near the end, not the case of the plug)
Look for heat discoloration on the ground electrode-should be near the end of the bend on the ground electrode(near the end, not the case of the plug)
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.
06-09-2003, 06:09 PM
#25
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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.
06-09-2003, 06:54 PM
#26
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.
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.
Last edited by KAAMA; 06-09-2003 at 06:57 PM.
06-10-2003, 12:09 AM
#28
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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!
06-10-2003, 10:59 PM
#30
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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....
