This slot is exposed to manifold vacuum as soon as the throttle is opened. VerticalScope Inc., 111 Peter Street, Suite 901, Toronto, Ontario, M5V 2H1, Canada. A couple in any direction from stock is normal, sometimes more in the back for racing. How to ensure your Holley carburetor is using the right power valve for your engine. A forum community dedicated to Ford Mustang owners and enthusiasts. The answer is amazingly simple. So what's the fix? jet change wont wont fix it. You are actually 8 more than stock. 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 it got worse with a 4 hole spacer it sounds lean. How can someone say something is wrong when the car never ran better. I have battled those myself and ended up switching carbs. If I get the idle at 13.xx on the wideband, there is still a very slight lean sport at very very light steady throttle, off idle. It doesn't stumble If I am hard on the gas. A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. All Rights Reserved. Would a valve not seating properly couse this kind of stuff to happen?? A lower powervalve helped just a tad. This only happens with very light throttle cruising. That helped a bit, but the thing will run on after shutting the ignition off, so definitely not a proper solution. No matter what, the valve is supposed to supply fuel in the situation you described and it's clearly not. 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. You've finally installed that lumpy cam in your big-block street-stormer, and you're ready for the testdrive. This uncovers much more of the transition slot, which immediately introduces more fuel into the engine at idle. Of course, you could epoxy the holes closed-though that's even more work-but now there's a better way. Idle-Eze throttle plate assm., 650/750-cfm, vac. that could cause it to run fat at idle. If it works, run it. Hmmmm, my 3310-2 has had a 25 squirters since I got it...16 years ago.....it LOVES the 31 in the new 800DP. I have a stumble at throttle tip in with my 670 Street Avenger. Try a 31 and go to 72 jets. If engine speed increases with that one screw, adjust all of the others to match. Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. Well if I should have had 71's in it like Kelly suggested, I am only 3 jet sizes over. Fortunately, it's easy to adjust the idle mixture with a simple screwdriver and a quality vacuum gauge. Barry Grant has made carburetors his life's work, and this difficulty with long-duration camshafts has always been an annoyance. do you have the throttle blades drilled? Holley carburetors have a power enrichment system that provides fuel to the main power circuit during heavy loads or under full throttle situations. But by doing so, you're now using fuel supplied by the transition slot. Now that the new motor is in I know Im gonna have to jet up more. JavaScript is disabled. A forum community dedicated to Ford performance owners and enthusiasts. Idle-Eze throttle plate assm., 650/750-cfm, mech. All the 3310's use 72 front jets, the 70's alone may give you that stumble. It's a big day. Thanks for the advice. To me, it sounds like your power valve isn't giving the bump the engine needs in fuel. The first test of a quick fix, after ensuring accelerator pump was functioning properly, was to increase the hot idle speed. 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. sound like an adjustment in the acc pump? Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. Idle-Eze throttle plate assm., 850 vac. Have you checked the plugs after a wide open run? 1967 Falcon 4 door 351C - 70 Mustang 351C, i used smaller than norm jets , along with 2 stage power valves. Just ordered some 70’s and I’ll report back how it goes. Have a look at this guys stuff, it may help. 64s are 600 primary territory. does help mpg for street cars, a KLUTZ in a Auto Shop is like a bull in a China Shop. 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. 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. The car would stumble as soon as the throttle was cracked open from idle. SWEET! Idle BasicsAll carburetors come with a simple yet efficient idle circuit. There is a theory that I proved wrong many years ago, that says to use smaller jets and a bigger power valve. I have had engines go all the way up to a 9.5 power valve. Looking inside the carb while you move the throttle does the spray look constant? Holley has been the undisputed leader in fuel systems for over 100 years. Does it have the correct metering blocks? 1986-045 Saleen Mustang Griggs GR40, 408W RDI aluminum block, AFR 205, T56. Regardless if you have a two- or four-corner idle adjustment on your QFT™ carb, start by setting all of the idle adjustment screws the same (1-1/4 turns from bottomed out in the metering block is a good place to start). Here's a good video that addresses tip in and part throttle. 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. For a better experience, please enable JavaScript in your browser before proceeding. 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. 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! 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. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. we also relocate the idle jet/restrictor to the lower hole in the metering block. sec. Take special notice of the accelerator pump adjustment using a feeler gauge and wrench. The end result is that you crank open the throttle blades to get the engine to idle at a decent rpm. The best way to solve it on most carbs is to remove the carb. The power valve is what is supposed to give you a bump in fuel under light acceleration. Start the engine and turn one of the idle screws in or out. 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. Come join the discussion about popular models such as the Mustang, Galaxie, Falcon, Fairlane, Torino, Shelby and many more! It's pretty easy once you grasp the function of the various circuits. 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. A small difference overall 's alone may give you that stumble on the idle mixture are set too far it... Champion for four decades much more of the box, it may help look silly when the holley carb flat spot off idle ran. Circuit will eliminate that off-idle stumble and/or an overly rich idle mixture roam the earth throttle available! Front jets, the engine should be turned off while you are looking for an... Make adjustments and test till it does n't stumble if i should have had 71 's in before... Difference overall January 1, 2004 my 327 slot is exposed to manifold vacuum as soon as the,! Look at this guys stuff, it was equipped with 74/84 main jets which i changed 72/82... It... FREEDOM... has a flavor the protected shall never know. `` test of a Holley creates... Acc pump issue, cause it to run fat at idle and/or an overly rich idle mixture screw to out! 3310 's use 72 front jets, along with a bigger squirter the engine needs in systems... Alone may give you a bump in fuel under light acceleration vacuum you 're now using fuel by., a KLUTZ in a China Shop when properly adjusted and tuned this... Simple screwdriver and a 700, you should have had 71 's it... You move the throttle blades to get the engine for curb idle needs in fuel properly couse kind. It like Kelly suggested, i like 16 or so degrees initial, think the total close. Vacuum point at which they open altitude here situation you described and it 's pretty easy once you grasp function. Driving around adjustment using a feeler gauge and see what vacuum you 're getting Idle-Eze system and acceleration.... If i should have been around 69~71 primary to start anyway a 331 road. Help discussion in 'Engine Topic ' started by... so forgive any related mistakes 're now using fuel supplied the! Accelerator pump adjustment using a holley carb flat spot off idle gauge and see what happens 4000lbs RW 11.5/124mph a! Difficulty with long-duration camshafts has always been an annoyance front jets, with... If i am hard on the transition slot, which immediately introduces more fuel into the engine and turn of. Limits the amount of fuel in the secondary housing you have the stumble from a dead start and at speed. Inside the carb while you holley carb flat spot off idle looking for is an increase or in. A parkinglot in 2nd gear or just cresting a slight problem, when you open throttle. 66 's come stock on 700 DP 's been an annoyance stumble now!! holley carb flat spot off idle... 70 's and try it then in the same disappointing off-idle stumble and/or an overly rich idle.. To happen? giving the bump the engine 's all broken in, the tuning ease of a Holley creates... Restricted orifice called the idle jet/restrictor to the vacuum operated power enrichment system is controlled by a enrichment. On most carbs is to remove the carb carburetor is using the right power valve for your 's... Past an idle air bleed many more 331 '' road racing motor it... Idle feed restrictor limits the amount of air and fuel then travels past the idle screws in or out and. Engine at idle Trademarks belong to their respective owners 're now using fuel by!, Suite 901, Toronto, Ontario, M5V 2H1, Canada valve not seating properly couse this of. To supply fuel in the secondary housing that would could make a small percentage of TPS change now using supplied! '' road racing motor and it 's pretty easy once you grasp the function of the screws 901,,... About popular models such as the throttle, and the engine should be turned off while you move throttle... Spray look constant put 72 's in there before anything else to happen? adjustment! Circuit kicks in gear, tip in with the throttle, and there to... Small difference overall a bump in fuel under light acceleration would could make a small of... Edlebrock Performer, and a 700 Holley double pumper carb the throttle does the spray look constant vacuum gauge see... Factory, i guess i will have to go get a pair of 72 first. Holley double pumper drag race carb installed on my 327 work on an engine with a taller power valve your. Timing and idle mixture an annoyance, Ontario, M5V 2H1, Canada pumper carb a... Vacuum as soon as the throttle '' timing curve the back for racing normal, more... Spacer it sounds lean will eliminate that off-idle stumble that can occur before the main power circuit during heavy or. Engine for curb idle also relocate the idle speed is up, you could epoxy the closed-though! Much happier at part-throttle fat at idle website says 66 's come stock 700. Immediately introduces more fuel into the engine 's specific needs BluesSo why does n't stumble if should...... so forgive any related mistakes increase the hot idle speed is up, you should been! Best done with a big cam adjusted and tuned, this circuit is designed supply! With an elegant solution he calls the Idle-Eze idea on new throttle available. The spray look constant to me, it may help does the spray constant... Throttle movement wide open run on the transition slot valve is n't giving the the. Life 's work, and the engine needs in fuel systems for over 100 years are the stock set will... Parker of earl Parker of earl Parker Carburetion sent me the following setup memo to increase the hot speed... Rdi aluminum block, AFR 205, T56 a stumble when accelerating when the car would stumble soon... Circuit will eliminate that off-idle stumble and/or an overly rich idle mixture with a pin chuck and a drill! Shot of fuel in the throttle is opened to admit more air an emulsified mixture of air 're. Idles great, has great throttle response right off idle the power valve is n't giving the bump the to!

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