It's a big day.

To me, it sounds like your power valve isn't giving the bump the engine needs in fuel. Hook your laptop up and increase your acceleration enrichment by a few miliseconds at a small percentage of TPS change.

The will make it a little richer on the transition circuit and at idle so you may likely have to go in slightly on the idle mixture screws as well. Holley has been the undisputed leader in fuel systems for over 100 years. 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. Once you have checked things like float level, transition opening, pump adjustment and such; you shouldn't need to touch them again.

JavaScript is disabled. jet change wont wont fix it.

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. The slot is connected to the idle mixture circuit upstream of the idle mixture screw and is "jetted" or controlled by a combination of the idle feed restrictor and the idle air bleed. When properly adjusted and tuned, this circuit will eliminate that off-idle stumble that can occur before the main fuel circuit starts. A forum community dedicated to Ford Mustang owners and enthusiasts. make sure it is on the idle circuit and not on the transition. If it got worse with a 4 hole spacer it sounds lean.

Typically, a restricted orifice called the idle feed restrictor limits the amount of fuel leaving the well up past an idle air bleed. Earl Parker of Earl Parker Carburetion sent me the following setup memo. Looking inside the carb while you move the throttle does the spray look constant?

In addition to this circuit, there is a tiny slot cut into the throttle opening on the primary side (and on all four barrels if the carburetor is equipped with four-corner idle mixture adjustment). Don't let all of these small details overwhelm you. 700 DPs have truck style boosters.

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.

sec. How can someone say something is wrong when the car never ran better. While this is a simple fix, the problem is that the carburetor can't be used on an engine with a less radical cam because the holes will create excessive idle speed. © 2020 Holley Holley carburetors have a power enrichment system that provides fuel to the main power circuit during heavy loads or under full throttle situations. A forum community dedicated to Ford performance owners and enthusiasts. Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. JavaScript is disabled. 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. Try 72 jets first, they are the stock set.

1971 Chevelle: L96 6.0, 232/244 cam, t56, 411's, 460whp/430wq...still trying for 11's.. 12.3 @ 115 1.89 60'. 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. Make these adjustments ¼ turn at a time. I have battled those myself and ended up switching carbs. The first test of a quick fix, after ensuring accelerator pump was functioning properly, was to increase the hot idle speed. Start the engine and turn one of the idle screws in or out. That is why they are jetted a bit low compared to the others. Hey guys, im trying to get my carb dialed in have have a slight problem. Now that the new motor is in I know Im gonna have to jet up more.

You've finally installed that lumpy cam in your big-block street-stormer, and you're ready for the testdrive. Read More. When I first read your symptoms, especially the acceleration stumble that none of the usual culprits fixed, it sounded to me like you have an air leak somewhere. The engine should be turned off while you are setting the adjustment on all of the screws. A lower powervalve helped just a tad. Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. 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.

Come join the discussion about popular models such as the Mustang, Galaxie, Falcon, Fairlane, Torino, Shelby and many more! If it works, run it. This portion of the idle circuit introduces additional fuel into the engine as the throttle is opened to admit more air.

you could try raising the float, that would could make a small difference overall. "For those that will fight for it...FREEDOM ...has a flavor the protected shall never know.". With the Idle-Eze system, the throttle blades maintain their proper relationship to the idle transfer slot so when the throttle is slowly opened, the transfer slot will supply the necessary fuel to overcome any part-throttle stumble. All Rights Reserved. IMHO and experience,sounds like bumping up the base timing a bit will take care of it. 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! They're numbered according to the vacuum point at which they open. 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. Just pull over in a parking lot and make adjustments and test till it doesn't hesitate. While I had the carburetor off I checked the accelerator pump squirters and noticed the front was a number 31 and the back was a number 35. Trademarks belong to their respective owners. Just ordered some 70’s and I’ll report back how it goes. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. RPM heads, RPM intake, FiTech EFI, Comp XE266HR roller cam, EDIS/Megajolt ignition, long headers), T5Z w/Steeda TriAx shifter, 9" Trac Loc w/3.89:1, 31 spline axles. Take special notice of the accelerator pump adjustment using a feeler gauge and wrench. 1986-045 Saleen Mustang Griggs GR40, 408W RDI aluminum block, AFR 205, T56. Your next step will be fine tuning. 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. 70 Maverick Grabber, 5.0 (Perf. This circuit is designed to supply additional fuel as the throttle opens before the main circuit kicks in.

We used it on a 4779 Holley used on a 331" road racing motor and it worked very well.

Cars and engines want what they want and that's all there is to it. Idle Eze throttle plate assm., 850 mech. If engine speed increases with that one screw, adjust all of the others to match. Bigger cams with less idle vacuum require larger holes. The power valve is what is supposed to give you a bump in fuel under light acceleration. 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. SWEET! So Grant came up with an elegant solution he calls the Idle-Eze system. Did you put the check ball back in the secondary housing? do you have the throttle blades drilled? Did you check/clean the filter already??? This slot is exposed to manifold vacuum as soon as the throttle is opened. Once the idle speed is up, you readjust your idle mixture screw to lean out the engine for curb idle. I have a QF 750 double pumper drag race carb installed on my 327. 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. The best way to solve it on most carbs is to remove the carb. Transition Slot Usage I can't argue with what works. Main jets don't usually have much of an effect on off-idle and acceleration stumbles., VerticalScope Inc., 111 Peter Street, Suite 901, Toronto, Ontario, M5V 2H1, Canada. That helped a bit, but the thing will run on after shutting the ignition off, so definitely not a proper solution.

10 jet steps say "big problem" somewhere. does help mpg for street cars, a KLUTZ in a Auto Shop is like a bull in a China Shop. The answer is amazingly simple. 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. Fortunately, it's easy to adjust the idle mixture with a simple screwdriver and a quality vacuum gauge. The Holley website says 66's come stock on 700 DP's. Of course, you could epoxy the holes closed-though that's even more work-but now there's a better way. I went to 64's because of the altitude here. 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. For a 700, you should have been around 69~71 primary to start anyway.

The end result is that you crank open the throttle blades to get the engine to idle at a decent rpm. Unfortunately, the tuning ease of a Holley also creates some tuning problems. You are actually 8 more than stock. It doesn't stumble If I am hard on the gas. 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. Only takes a few seconds.

Start the engine and turn one of the idle screws in or out. it runs great other than a flat spot right off idle. put 70 idle bleeds in and re-adjusted carb. *69 SS 502 EFI /224-228* HR/9.8:1/T56/3.90/ 4000lbs RW 11.5/124mph -with a "top fuel" timing curve. Would a valve not seating properly couse this kind of stuff to happen?? 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. That's a fair amount of cam for a 355,I like 16 or so degrees initial, think the total is close. Well if I should have had 71's in it like Kelly suggested, I am only 3 jet sizes over. 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.

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