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holley carb flat spot off idle

The Holley website says 66's come stock on 700 DP's. Would a valve not seating properly couse this kind of stuff to happen?? JavaScript is disabled. The power valve is what is supposed to give you a bump in fuel under light acceleration. Some my dad use to say, "when you can tell a engine to read so it knows what it's suppose to do, then this stuff will be a lot easier. Bigger cams with less idle vacuum require larger holes. Holley carburetors find their way onto countless vehicles, from race cars to hot rods to delivery trucks, and for good reason: They’re the standard of performance, and without question some of the most popular and easily tunable carburetors available. does help mpg for street cars, a KLUTZ in a Auto Shop is like a bull in a China Shop. But by doing so, you're now using fuel supplied by the transition slot. Fortunately, it's easy to adjust the idle mixture with a simple screwdriver and a quality vacuum gauge. It'll do what it wants too". That is why they are jetted a bit low compared to the others. it doesnt matter what gear im in, if im just cruising down the road barely on the gas and go to give it a little more, just to increase speed 5mph it stumbles (almost like falls on its face) then picks up. If you have a fixed-idle jet, resizing is best done with a pin chuck and a jet drill set. Here's a good video that addresses tip in and part throttle. A forum community dedicated to Ford performance owners and enthusiasts. I can't argue with what works. Make sure the accelerator pump is tight and squirts with any throttle movement. sec. Lean transition circuit is more likely. Idle Eze throttle plate assm., 850 mech. Read More, We head to Lake Tahoe, California to find out if Ram’s new Raptor fighter has what it takes to dethrone the king of off-road pickups. CHP/CPR (Coast High Performance) / (Custom Performance Racing Engines)347 lasted a whopping 500 miles due to poor machining, metal debris in main bearings, damaged cam bearing and a balance job that was off 64ozs! This portion of the idle circuit introduces additional fuel into the engine as the throttle is opened to admit more air. Start the engine and turn one of the idle screws in or out. Come join the discussion about performance, production numbers, VIN decoders, modifications, troubleshooting, power adders, DIY tutorials, and more! You've finally installed that lumpy cam in your big-block street-stormer, and you're ready for the testdrive. This only happens with very light throttle cruising. This slot is exposed to manifold vacuum as soon as the throttle is opened. The car would stumble as soon as the throttle was cracked open from idle. Did you put the check ball back in the secondary housing? If it got worse with a 4 hole spacer it sounds lean. Did you check/clean the filter already??? If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. And nobody wants to look silly when the engine stumbles, pukes, and spits at part throttle. I had a slight step into stumble while driving around. It's pretty easy once you grasp the function of the various circuits. jet change wont wont fix it. This is interesting. 10 jet steps say "big problem" somewhere. If the carb is not equipped with replaceable jets, insert a fine piece of fuse wire (with a bend in it so it does not go all the way into the idle well) to block off some of the air going into the air corrector jet. So Grant came up with an elegant solution he calls the Idle-Eze system. SWEET! Take special notice of the accelerator pump adjustment using a feeler gauge and wrench. For a better experience, please enable JavaScript in your browser before proceeding. do you have the throttle blades drilled? Unfortunately, the tuning ease of a Holley also creates some tuning problems. Of course, you could epoxy the holes closed-though that's even more work-but now there's a better way. Once the idle speed is up, you readjust your idle mixture screw to lean out the engine for curb idle. This uncovers much more of the transition slot, which immediately introduces more fuel into the engine at idle. 83 Capri RS T-Top 302, Afr 195 Renegade,11.2 compression, e303 cam, Scorpion 1.82 race series rockers, TFS-R, X3Z w/Tweecer RT, T56 Magnum, 2 1/2" Pypes X pipe w/2 chamber Flowmaster mufflers. Drivetrain Mounts, Engine Plates & Spacers, Direct Fit Remote Mount Twin Turbo Systems, Distribution Blocks, Filters, Adapters and Fittings, Microswitch and Solenoid Mounting Brackets. Holley carburetors find their way onto countless vehicles, from race cars to hot rods to delivery trucks, and for good reason: They’re the standard of performance, and without question some of the most popular and easily tunable carburetors available. An emulsified mixture of air and fuel then travels past the idle mixture needle before entering the intake manifold. Come join the discussion about popular models such as the Mustang, Galaxie, Falcon, Fairlane, Torino, Shelby and many more! put 70 idle bleeds in and re-adjusted carb. We used it on a 4779 Holley used on a 331" road racing motor and it worked very well. With engine warmed up, and cruising along, if I just breath on gas pedal a tiny amount, car hits super lean on wideband and lean surges. Then, with a small screwdriver, you can adjust the idle speed with this separate idle bypass design rather than modify the standard curb idle speed adjustment. The best way to solve it on most carbs is to remove the carb. Hey guys, im trying to get my carb dialed in have have a slight problem. Read More, Over the course of just seven months, this ’67 Dodge Dart was transformed from a lively cruiser into a street and strip restomod that shows just as well as it goes. Could be very rich at the top end. Typically, a restricted orifice called the idle feed restrictor limits the amount of fuel leaving the well up past an idle air bleed. The first test of a quick fix, after ensuring accelerator pump was functioning properly, was to increase the hot idle speed. I went to 64's because of the altitude here. IMHO and experience,sounds like bumping up the base timing a bit will take care of it. The first step is to ensure that there are no vacuum leaks, so check all the hoses leading to and from the carburetor and intake manifold for cracks. I have a stumble at throttle tip in with my 670 Street Avenger. If the carb is clean and in good condition and the engine has enough timing in it you could try putting smaller idle air bleeds in it, that would richen up the transition and get rid of the flat spot. Read More. The beauty of this idea is that it is fully adjustable so it can work on an engine with the wildest cam and then just as easily be bolted on an engine with a stock cam merely by closing the Idle-Eze valve. Idle-Eze throttle plate assm., 650/750-cfm, vac. 1967 Falcon 4 door 351C - 70 Mustang 351C, i used smaller than norm jets , along with 2 stage power valves. On the bottom right side of the rear barrels throttle shaft is a small screw that can be used to open the rear slightly so the front can be closed some. If you're cruising at very high manifold vacuum, go with a taller power valve. Big Cam BluesSo why doesn't this circuit work on an engine with a big cam? Wow, who would of thunk that? I am posting this so that someone might avoid the week of headaches I had trying to get rid of an off idle stumble on my '64 Galaxie. To modify an existing carburetor, all you have to do is disassemble the main body and baseplate and drill a hole through the carb stud hole, and you're ready to reassemble the carb. The engine should be turned off while you are setting the adjustment on all of the screws. Also in Tools, Shop Equipment & Chemicals -, Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. For a better experience, please enable JavaScript in your browser before proceeding. To me, it sounds like your power valve isn't giving the bump the engine needs in fuel. How to ensure your Holley carburetor is using the right power valve for your engine. What squirters in there? So what's the fix? https://www.tapatalk.com/groups/racingfuelsystems/index.php, VerticalScope Inc., 111 Peter Street, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Once you have checked things like float level, transition opening, pump adjustment and such; you shouldn't need to touch them again. Regardless of how you approach the repair of this problem, the key is the proper relationship of the throttle blades to the idle transition slot. Trademarks belong to their respective owners. Does it have the correct metering blocks? This reduced vacuum requires more throttle opening to feed sufficient air to the engine since there is less of a differential between manifold vacuum and atmospheric pressure. The first result of a long-duration camshaft with lots of overlap is drastically reduced idle vacuum. sec. Looking inside the carb while you move the throttle does the spray look constant? 1986-045 Saleen Mustang Griggs GR40, 408W RDI aluminum block, AFR 205, T56. Earl Parker of Earl Parker Carburetion sent me the following setup memo. Improperly set idle mixture screws are often the reason for carburetor symptoms such as hesitation, rough idle, backfire, stalling, hard starting, engine surge, and more. Hmmmm, my 3310-2 has had a 25 squirters since I got it...16 years ago.....it LOVES the 31 in the new 800DP. Only takes a few seconds. You drop it in gear, tip in the throttle, and the engine dies. stock nozzle is a 31, i guess i will have to go get a pair of 72 jets and see what happens. It's a big day. Your AFR gauge will also work for this... you could just jump up to the next size and see if that corrects your issue. © 2020 Holley sec. sound like an adjustment in the acc pump? This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Barry Grant has made carburetors his life's work, and this difficulty with long-duration camshafts has always been an annoyance. Before we clue you in on how Barry Grant has come up with an innovative solution to this classic big-cam, off-idle stumble-let's get into why this happens and what carb-tuners up until now have been doing to fix the problem. Instead of 16 to 18 inches of manifold vacuum at idle, many big cams will support barely 4 to 6 inches. All the 3310's use 72 front jets, the 70's alone may give you that stumble. If the primary side throttle blades are set too far open it can cause a flat spot like that. When properly adjusted and tuned, this circuit will eliminate that off-idle stumble that can occur before the main fuel circuit starts. it stumbles before you even get into the main jet circuit, and at cruise your still in the idle circuit and you give it gas its going lean, the car finally picks and runs ok when the main jets are just catching up. 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