Holley Carb Wot Stumble

The power. Holley carb adjustment question: I was wondering if anyone knows what the proper setting should be for an accelerator pump spring (I think that’s what it’s called). If you had a holley I would say try a different cam for the accelerator pump or a bigger squirter but I really don't know how to make many adjustments on a stock ford carb. 3 circuit questions on the net. If I tried to get it up using less throttle, there was no stumble but it takes longer (obviously). For Carbed engines, you need to up the size of the jets to flow about 20% more for the primary, and 35% more for the secondarys, and tune from there. (2) If dirt is in the fuel system, clean the system and replace filter (s) as necessary. Mopar Racers Forum. It worked OK, but I've kind of had it with the "emissions" carb because between the heavy duty fan clutch that I had to put in it to keep the motor cool with the AC on, and the high-energy ignition that's now in it, I can't get the idle mixture rich enough to prevent an off-idle stumble with a curb idle speed of 750 rpm in park. Carb is set up w/ PV, etc. 7L(350) motor that uses a Holley 4175 spreadbore carburetor. I can get 20" hg at idle, steady gauge with no fluctuation. Set your idle & timing, then adjust idle screws for highest manifold vacuum. Everything you need to know about Vac Secondary, Double pumpers, HP Series, Avengers, and the Dominator. only on level ground will it take off after the bog senario. They also have an accelerator pump to compensate for quick throttle actuation. Holley Carburetor Tuning: Idle Circuit Mods for High Duration Camshafts - Duration: 12:02. While all the Holley carbs being discussed are all four-barrel carbs, they don't all operate all the same way. A carb running rich, as well as a carb running lean, can cause an off-idle stumble or hesitation upon acceleration. RPM intake, Doug's Headers 3" Pypes exhaust. 050, and peak power at 7,600 rpm. Fits all Holleys where the screw goes in the metering block on the side. Now lets take another 600cfm carb, Holley's #1850. Figure 1—Carburetor torque sequence (all Holley carburetors) WARNING: Overtightening may result in a warped or cracked carburetor throttle body. Too little transition slot exposure on either end can cause a hesitation or stumble as well. This is a common problem with any carb. #1 doesn't let the arm contact the profile correctly in my case. I had it rebult/restored by Pony Carb about 2 years ago, but haven't been able to use it until I finished the engine. You can get a diaphram spring kit from holley as well with an assortment of different spring rates. Yep, hard to beat a Holley for WOT power production. What are Holley carburetors made from? Most Holley carburetors are made of aluminum to reduce the part's overall weight. We started by going down two jet sizes on the primaries (74 to 71) and two jet sizes on the secondaries (99 to 97) as recommended by Holley. I received some advice that it might be caused the a lean accelerator pump. i de-jett the carb and put a metering plate in to make it a 600 using number 66 jets and number 134-9 metering plate for the secondary side. If it's weak, just get a new one. Racing and Automotive, How to's and advice 114,522 views. My theory is that the engine speed is too low and is not generating enough low pressure to pull enough fuel into the air stream (the air volume is high due to WOT position). They are suppose to have a leaner Idle circuit than the 8007 carb. Holley Carb Baselining/Tuning It's been a while since I've been asked a carburetor-related question, but this one came up this week so I figured I'd do a little writeup. GAS CARBURETORS MAINTENANCE. Some people do not run a power valve at all, and jet up the carburetor to compensate for not having the additional fuel available at WOT that the PV would normally provide. Also put in a stiffer (8 hg) step-up spring for the primary jets to speed up transition in case of fuel demand. I am considering swapping out the existing Holley carb on my 72 340 for the OEM Carter Thermoquad model 6139S. Holley carb backfire keyword after analyzing the system lists the list of keywords related and the list of websites with related content, in addition you can see which keywords most interested customers on the this website. Trying to identify my carburetor Classic Tech. Disconnect the TV cable and main carburetor linkage cable. The carb is a modern interpretation of good, proven carb designs, uniting aspects of the TQ and QJ. If your intake manifold is an ECZ-8425-A and the studs from one corner to the next are approximately 3. When selecting a carburetor for your engine, don't overdo it. This is very much like the carb found on the 1st gen. Holley carb tuning Welcome to Rods 'n' Sods, the most active and friendly UK Rod and Custom website. the carb was bought new around 1990. Holley carb setup. The kits for this carb are expensive because Holley doesn’t sell very many. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle position to the main metering system. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. The secondary side of this carb does not use a power valve to balance the fuel flow between the primary and secondary, so it uses 6-step larger 73 jets. Clean all parts with carb cleaner and assemble in reverse order and setup. Idle - At idle speed, the carb runs solely on the curb idle discharge port. Holley/Demon Carb stumble. Look at it like this a 650cfm carb can flow 1200cfm, but you'll be pulling about 6 inches of vacuum in the manifold to do it. Just bend the tab a little at a time like most bike carbs. Disconnect the TV cable and main carburetor linkage cable. Holley carburetors powered every Monster Energy NASCAR® Cup team and nearly every NHRA® Pro-Stock champion for four decades. If you can tune a carb to deliver a consistent A/F within this range, the engine will usually run at its full potential from off-idle to wide open throttle. ALCOHOL CARBURETORS. You can get a cable button off of a junk GM vehicle and weld it to your throttle valve lever. Before changing the size of the shooters or the pump cam, be sure the accelerator pump is adjusted correctly- no play and fuel from the shooters the instant the throttle shaft is rotated, and about 0. all my life, never had a street car that I really had desire to fool with. When I blip the throttle, it stumbles/bogs. I have the vacuum advance on the ported spot of the carb. Our Quick-Fuel Products are priced so low we can't advertise them under the terms of our "Minimum Advertised Pricing- MAP" Agreement. 5:1 ratio at part-throttle cruise. yeah! yeah! wot he said!!:D I've got a VC 202, I've had the stock carb on it, a rebuilt Holley 350 on it, and now have a rebuilt XF 250 weber on it. I built a similar carb with a Holley HP body, QFT billet metering blocks and baseplate. Holley carbs come with a standard shooter size which differs by carb list#. 0 built for my road race Mustang. I've had the car running for about 6 months and have this lean stumble when lightly rolling in the throttle. Observe the pump jet in the carburetor, and with your hand, work the carburetor throttle to the wide-open position. We love our carburetors. I have an off idle stumble. The goal for both systems is the same, giving the carburetor the ability to adapt to the varying idle, off-idle transition, cruise, and wide open throttle conditions. The Holley has evolved through hundreds of variations and dozens of. As rule of thumb, set your fuel pressure to these ranges based on the carburetor brand: 5-7 psi for Holley, Quick Fuel, AED, Willy's, or Summit Racing; or 4-5 psi for Edelbrock or Jet. and is also were i found a couple of pieces of alu that. Fine-tuning the carb in this manner will improve part-throttle operation and should eliminate that annoying off-idle stumble. Holley carbs come with a standard shooter size which differs by carb list #. Holley carb tuning Welcome to Rods 'n' Sods, the most active and friendly UK Rod and Custom website. This allows a faster air speed to feed the engine and no "toilet flushing". It was about that time that I noticed an off idle stumble, or flat spot, begin. The engine was running fine. Really happy with it so for but its taking some adjusting to get it dialed in to my engine. Holley 4160 carb, street performer intake, double hump heads, stock manifolds, and a slightly mild cam (I do not have the specs) and recently replaced distributor running 13° initial and 34° total. _____ Patrick James-President. Was running a conventional Holley double pumper and had the carb pretty well dialed in but I always had a very slight hesitation to wide open throttle transition and was always tweaking the carb as the weather changed. Possibly damaged by a backfire condition. The carb selected was a 1050 Holley Dominator, which worked out very well. Identifying the Carburetor’s Circuits of Operation. Compare and save at FindersCheapers. The carb is stock out of the box. Holley additionally has a package for Gen three Dominator carbs that could be very compact and bolts on to the bottom plate. A common problem with just about any carb is the throttle shaft bores wear which causes vacuum leaks and will eventually effect the way things operate like the choke. Electric chokes come on the Chryslers and Chevrolet Chevette, so should be readily available from any parts store. Number 37 squirter. The Holley power valve is a great tool allowing you to really move the fuel curve around. If you're determined to use that 750 Holley, you can still get it to run very nicely with some. i dont know the part. If you went from a 2BBL to a 4BBL, the cable is usually too short of stroke for a Holley type carb, and the throttle cable bracket is generally at the wrong angle both horizontally and the angle upward to a taller carb and linkage. Holley carburetors have powered almost every NHRA Pro–Stock champion and every NASCAR Sprint Cup team for 40 years. You can get a diaphram spring kit from holley as well with an assortment of different spring rates. Edelbrock 1109 (for 8BA) 3x2 manifold is a good choice. Re: Holley Carb Off Idle Stumble Is Pissing Me Off Broke Crank may have it. this is the main body Proform Main Bodies for Holley Carburetors 67107C and this base plate Proform Billet Throttle Base Plates 67156 So that the complete carb would have to be a 850. A carb running rich, as well as a carb running lean, can cause an off-idle stumble or hesitation upon acceleration. The responds and transition from idle to mid carb to hi speed jets is a lot better because of the air flow / velocity over the larger carbs. the carb was bought new around 1990. bothered messing with the idle circuit to cure a “bog” situation that occurs when going from idle/just off idle to WOT in a tenth. Holley suggested a 650 double pumper for an auto car which already tells me what I have heard about the recent Holley tech support has gone by the wayside. If you put the clamp on the black plastic part of the cable housing, it is possible to crush it on the cable. Nx Nitrous Express. Find Holley TPS Kits 534-214 and get Free Shipping on Orders Over $99 at Summit Racing! If you're running an electric choke Holley carburetor and are having trouble figuring out how to get that electronic overdrive transmission to work, Holley has the perfect solution for you. Page 2 of 3. This is really my first real carb tunning experience, been tunning Hilborn F. aedcompetition. Optional housing covers are available that allow the springs to be changed without disassembling the carburetor. You can't just put in a new carb and expect to get optimum performance out of it. 9% pure is preferred. Initially the vacuum advance was hooked to a full vacuum port. How to tell what size carb you need: You take the engine cubic inch and multiply by the maximum RPM and divide by 3456. Holley rates their carbs at 1. Holley carburetors powered every Monster Energy NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Off idle to WOT stumble/bog. Holley type carbs come with a standard shooter size which differs by carb list #. If you want lots of adjustability and have the knowledge to tune a carb, go with QuickFuel and consider the annular booster option. Fortunately Holley’s made a kit to avoid that, a quick change kit so you can change the spring in 1. It also had a stumble when accelerating when the car was already at speed. They also have an accelerator pump to compensate for quick throttle actuation. Looks like the thottle moves a bit before and gas comes out of squirters and the pump arm is contacting the pump lever as it starts to move when touched. I had always just installed whatever came in the rebuild kit. 3 circuit questions on the net. Apply sufficient closing pressure to the choke lever to provide a minimum valve opening without distorting the diaphragm link (which connects the choke lever to the vacuum. On the manifold there is a channel machined into the surface which lines up with holes in the butterfly portion of the carb body. OK put in that other new plug, this time drive the car hard but do not let the secondaries open, you may want to leave the air cleaner off so you can hear the carb working and keep it off that deep howl that the secondaries make when they open. The carb book by Ulrich and Fisher explain a way to test to see if the PVCR is the correct size. I've changed the jets to 56/67, Nozzle to. Choosing the Right Power Valve for Your Holley Carburetor April 14, 2015 Randy Bolig Drag Race 101 , General Engine , Guest Columns , How-To and Tech Tips , Tech 5 When it comes to tuning a Holley carburetor the power valve has always seemed a mystery to many. HIGH PERFORMANCE TUNING INSTRUCTIONS FOR HOLLEY PERFORMANCE CARBURETORS 199R7849-2 NOTE: These instructions must be read and fully understood before beginning installation. Any port at the very bottom of the carb (in the aluminum baseplate) will pull manifold vacuum, which is strongest at high vacuum situations such as idle and slowing down, and weakest at low vacuum situations such as wide-open-throttle (WOT). 0" Hg at wide open throttle. Stalling when it's cold can also be caused by a fuel leak problem inside the carb. But I have found over the years that if you buy the correct carb, the factory setting is always in the ballpark. Since the Bear Stop uses its own set of secondary butterflies to regulate air/fuel flow, your carburetor operates at full throttle throughout the run. 3 speed manual 4. Air/fuel ratio is adjusted by turning the idle mixture screws. A level on the air horn shows the carb toward the front of the truck do to engine angle. Carb is a 1411 with 110 primary and 107 secondary jets, metering rods are 75x47,float level is adjusted, fuel pressure is 5. by Blown496 » 12:13 AM QFT 1050 (4150) annular boosters carb going rich under hard braking. I borrowed a friends exact carb, and he says he has a different spring for the vacuum secondaries, and possibly an upgraded plate of some kind. Re: Problems with new Holley Avenger Carb When it comes to the Holley street avenger the only smart question I asked was why didnt I get the double pumper instead lol. If you experience a bog or hesitation off idle, you can try a higher # (larger) shooter size. The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. The single hole job is for a 50-cc pump, while the others are used on 30 cc pumps. Note: I'm cheap so I have one quick change kit and move it from car to car tunning in the carb. 2 range and then i have terrible stumbling issues under light throttle. I could take any Holley carburetor right out of the box, slap it on your engine, with the only modification needed other than basic tuning be possibly changing the power valve based on your idle vacuum signal, and it would perform better than BM described his situation. up to the rev limitter, gets 17 mph on the highway when I'm not gunning it, and has very good drivability. Possibly damaged by a backfire condition. This is a discussion on holley carb on 2. The 650cfm Holley on my 390 stumbles off-idle under load (like when an RV trailer is hitched, or some other heavy load) and I have to feed the throttle in gently to keep it from dying. Was running a 6. Holley jets, Eddy like (although Demon specific) stepped primary metering rods and springs. Re: Carb tuning question - mixture screw vs. Before connecting the linkage, operate the throttle lever to assure the correct travel (no sticking or binding), by opening to wide-open throttle and back to closed throttle several times. Re: Holley stumble. There is more to your bog than just leaning out the Carb. Keihin carb stumbles and dies on wot - Answered by a verified Marine Mechanic We use cookies to give you the best possible experience on our website. While WOT is held open, using a flat screwdriver, push the lever down and take a reading, it should be. Although this is a good carb, I think I have enough cam and head work to take advantage of a bigger carb. Well, engine is rebuilt in my vette and the rear is now in. ok well, the leanest i can get the car to idle is in the 15. Move it open and closed a few dozen times. corrector plate 2. I don't know about 94's, but on a regular holley the power valves don't really do anything immediately off idle, that's the job of the accelerator pump. Mixture Screws: Turn clockwise until the engine starts to stumble and backout screw 3/4 turn. for a distributor i have an accel. I built a similar carb with a Holley HP body, QFT billet metering blocks and baseplate. This is a discussion on holley carb on 2. 788 or lighter on specific gravity at 75 degrees F. If you had a holley I would say try a different cam for the accelerator pump or a bigger squirter but I really don't know how to make many adjustments on a stock ford carb. 015-inch feeler gauge, and crank the carburetor to wide-open throttle. Jet extensions and notched float in the rears. 5 turns out, which gives me an average 13. Because if I crack the throttle and get the revs up, then whack it open, its fine. The “Bog” simply means the engine is not receiving enough fuel when you go to wide open throttle. There is an incline then nose drops down and a 90 degree left is pretty sharp under power with traffic bearing down. Holley carbs come with a standard shooter size which differs by carb list #. (talking WOT conditions only). 1974 Dodge 360 Holley Carb in a Coachmen Motorhome. Disconnect the TV cable and main carburetor linkage cable. I'd change the secondary spring to one thats more heavy. Product Video. First thing he had me do when I got there is swap out all my -06AN fuel line to -08 up to the regulator and from the two outputs on the regulator, -06 to the carb. Stalling when it's cold can also be caused by a fuel leak problem inside the carb. Holley carburetors powered every Monster Energy NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Your carb must have one of these little nipples in the primary bore or the secondary will not open like it should. I might need to determine if buying a better carb is the right decision. Holley does a pretty decent job of supplying a ready-to-run carb, so the jetting, pump cam, shooter sizing, and spring rates are usually pretty close. a double pumper is a 4 barrel carb. ) This week I visited a fellow who works with Holley, he handed me this experimental 2x38 to stare at (this prototype is not fully functional). 13:1 355 sbc, trick flow 2. You may just look into the power valve for sure. I runs great, fires right up with initial timing at approximately 18°, not sure what the complete timing is with vacuum advance, but doesnt changes little when hooked up to manifold vacuum advance or progressive-front port. It started with a ignition problem and then I took off a quadrajet that the secondary didnt open and someone gave me this holley and I cant quite dial it in. Set your idle & timing, then adjust idle screws for highest manifold vacuum. Tick Performance is proud to be a warehouse distributor for the entire Holley product line. But thats why i got it because it is so adjustable. Description. (talking WOT conditions only). Holley Carb Stumble Fix pt-1 - Duration: How to Adjust Tune Holley Carb Carburetor Tutorial Instructions. Pull the carb and spray a bunch of WD-40 on the shaft where it goes through the throttle body. I was hoping this new one from Holley would be good right out of the box. 015-inch feeler gauge, and crank the carburetor to wide-open throttle. Best price is Amazon. When I increase the primary jets it becomes overly rich. Holley carb adjustment question: I was wondering if anyone knows what the proper setting should be for an accelerator pump spring (I think that’s what it’s called). Available from #50 to #100. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. The car was running so much advance at idle, it had to be retarded to idle smoothly. If mounting a Holley to that manifold you absolutely need that plate- there will be a huge gap near the secondary side of the carb. This could be caused by several things; 1) Dirt in one of the needle and seats. Mixture Screws: Turn clockwise until the engine starts to stumble and backout screw 3/4 turn. Re: Holley Carb Off Idle Stumble Is Pissing Me Off Broke Crank may have it. Choosing the Right Power Valve for Your Holley Carburetor April 14, 2015 Randy Bolig Drag Race 101 , General Engine , Guest Columns , How-To and Tech Tips , Tech 5 When it comes to tuning a Holley carburetor the power valve has always seemed a mystery to many. 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. Holley carburetors have four distinct circuits of operation: idle, off-idle, cruise, and wide open throttle. Finally, there is a long drift lean from 4750 rpm. A single barrel carburetor will normally squirt a single stream; while a two or four barrel carburetor will normally squirt 2 streams. Not sure what a Holley 401 is, but here goes. Holley running rich. 5 within the Drivetrain forums, part of the CJ Forums category; has anyone converted their 2. 31 OpenSSL/1. Click on picture to enlarge. They also have an accelerator pump to compensate for quick throttle actuation. I borrowed a friends exact carb, and he says he has a different spring for the vacuum secondaries, and possibly an upgraded plate of some kind. 0L LS engine was pulled from a junk yard and topped with Holley’s new 2x4 dual plane intake and two Holley carbs. New edelbrock carb bogs & surges at wot. The goal for both systems is the same, giving the carburetor the ability to adapt to the varying idle, off-idle transition, cruise, and wide open throttle conditions. We sell a cable correction kit for Holly and Edelbrock carburetors. Holley rates their carbs at 1. One thing to consider on Holley CFM ratings is how they flow rate their carburetors. 550 cfm is great for a mild modified motor. This will not fit some early models of Holleys and some versions of the Holley Dominator. Runs better, but when I switch the ac on, the idle drops too low. It is a 289 with 9. The car idles smooth, runs strong at W. I tried to tune out that off idle stumble when I had time for several months thinking that Chevy had a reason for using the standard screw. You can see what I’m talking about in this link. We also tried a 350 Chevy equipped with a long-duration cam and a Holley 750-cfm 0-3310 vacuum-secondary carb that suffered from a bad off-idle stumble and a pig-rich 10. and is also were i found a couple of pieces of alu that. On some carbs changing the spring/weight is easy and aids tuning, but on others like the Holley it’s tricky to do on the engine and the choke has to be removed. Off Idle Stumbles Was curious a good place to start with some off idle stumble when the car gets some heat into it. Operate the carburetor throttle lever by hand to ensure the correct travel (no sticking or binding) by opening to wide-open throttle and back to closed throttle several times. I've also been using the #2 hole exclusively on cam. OK I have to take back some on my previous post because they were incorrect I did some more investigation today found out my fuel pressure at carburetor is one and a half pounds my vacuum gauge was not Sarah without broken got a new one not pulling 22 inches of vacuum pulling only 15 I’m going to first take care of the fuel pressure then I’ll take care of the power valve. 5) from an original 6. If your 650 CFM carb seems to work for you then stay with it. So far, I've stepped up to 35 squirters from 28's. Re: Need Carb Tuning Advice Again 8896 Holley 1050 cantedvalveFord400 on September 28th 2015, 7:27 am this is an old thread, I'm compelled to revive it, cuz there's a lot of these 2-circuit vs. Summit racing sent us four of the most popular off-road carburetors including a Holley 750-cfm, a brand-new model Holley Street Avenger 670-cfm, an Edelbrock Performer 750-cfm, and an Edelbrock Q. 0L LS engine was pulled from a junk yard and topped with Holley’s new 2x4 dual plane intake and two Holley carbs. Holley are great carbs, but can be a real pain in the ass to rebuild. Vacuum secondaries would be the best of both worlds, but hate to take carbs off that only have about 8,000 miles and spend more money to swap to different carbs. Well, little update around 2000 rpm, maybe more like 2250 rpm my air fuel gauge gets dangerously lean like um, the lights went down to the red then went out, and the car began to surge and have a lean misfire. Transition slot exposure is critical because it affects both idle quality, idle air / fuel mixture as well as 'tip-in' or 'off-idle' response. If mounting a Holley to that manifold you absolutely need that plate- there will be a huge gap near the secondary side of the carb. adjust the secondary "idle speed" screw about another 3/8 of a turn more. Reconnect the throttle and transmission kickdown linkage and throttle return spring (Holley P/N 20-89). Re: Tuning a Holley to Run No Power Valve « Reply #5 on: May 13, 2009, 11:55:27 am » Years ago I did this on my Mach I with a 429, it was a bracket car and it worked great, it also made tuning allot easer but I'm a dope on carb tuning so this was just to make it easier on me but I'm not sure how good it will be on the street. I noticed it had #55 on the jets. Going up to a 35. 5:1 at low-load cruise, we’ll save a few bucks on fuel. They are suppose to have a leaner Idle circuit than the 8007 carb. Buying a replacement part for your vehicle can be an intimidating experience. 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. This is really my first real carb tunning experience, been tunning Hilborn F. Holley Carburetor Full Power Circuit Calibration Guide July 27, 2015 by Muscle Car DiY Strange as it may seem, the main jet on a Holley carb is not what you should be using to calibrate the WOT mixture delivered to the engine. Holley idle mixture screws. The fuel tank is like new inside and out only about 5-6 years old. If your 650 CFM carb seems to work for you then stay with it. this is the main body Proform Main Bodies for Holley Carburetors 67107C and this base plate Proform Billet Throttle Base Plates 67156 So that the complete carb would have to be a 850. That lessened the stumble, but under WOT stabs its definitely still there. The fuel bowls and main body are one piece on the Street Demon (left), while the traditional Holley has removable metering blocks (center) and side-mounted fuel bowls (right). The single hole job is for a 50-cc pump, while the others are used on 30 cc pumps. Adjust each idle mixture screw (Figures 3 & 4) 1/8 turn at a time, alternating between each screw. Gasket street scoop and install an air cleaner or air pan as that Street Scoop has caused carbs to go lean at wot as it forces air over the top of the vent tubes and makes a vacuum in the bowls. (talking WOT conditions only). It runs and idles good just a random pff that I feel as It drives i can be on the freeway and it will off sorry it's not quite a pop more of a little stumble. I think my problem might be the carb itself. Idle is good put I have an off idle stumble then a really nice accelleration! It has 76 jets pri and sec, 45 pv pri and sec (9 to 10 inches in drive), and 31 long tube squiters, 30cc pri pump and 50cc sec pump. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. 5 inches of manifold vacuum, if the vacuum is high than that the carb will flow more than it is rated for, if it's lower than that it will flow less than what it is rated at. I built a few of those, and they required minimal tuning to get dialed in. I was trying to log a change to the WOT curve with just a swap of HSAB, my WOF A/F ratio didn't change any great amount and still is between 12. Holley carburetors have powered almost every NHRA Pro–Stock champion and every NASCAR Sprint Cup team for 40 years. First thing he had me do when I got there is swap out all my -06AN fuel line to -08 up to the regulator and from the two outputs on the regulator, -06 to the carb. Power Valve Tuning. the holley 4 barrel is the best carb out there. Went out for a ride with the WB idle read 14. I had always just installed whatever came in the rebuild kit. Holley recommends at least 3/4 inch of clearance between the carb and the hood or between the air cleaner and the top of. Skip navigation Sign in. When I blip the throttle, it stumbles/bogs. I only taking a guess here. All of the adjustment info that you need is on Holley's web site. Edelbrock air gap intake with 1" spacer and the Holley 770 carb Spectre 14" ultra flo air cleaner. Thread Tools. On CCS carburetors, the large sight glass windows allow float level setting without having fuel escape from the float bowl. I am considering swapping out the existing Holley carb on my 72 340 for the OEM Carter Thermoquad model 6139S. Edelbrock is the most respected name in performance. 5:1 ratio at part-throttle. Holley carburetors powered every Monster Energy NASCAR® Cup team and nearly every NHRA® Pro–Stock champion for four decades. That was another thought to the stumble, though the squirt seems to come in early, but may need to be more agressive. If using an EFI system, Holley. I primarily build engines fed by the 2x38 downdraft carb, from stock to perfomrance to race. Runs well, except with the quick snap of the gas to the floor. This meant that at WOT, with no vacuum, there wasn't enough total advance and it bogged like a dog. Light throttle stumble, Holley carb. Set the idle speed using the curb idle speed screw 2. 050 490/508 lift. If they open too late, you lose power. We aim to cater for a wider range of tastes here from Hot Rods & Street Rods all the way through to Bikes and Trucks. I installed a Holley in tank retrofit pump and sending unit. From stumble to hesitation | Ignition timing and carb issue with 340 « on: July 18, 2013 - 04:13:55 pm » The tired old Carter Thermo-Quad 6139S of my'72 Challenger 340 with A727 needed replacement. Lean Jetting. It's more than likely not enough pump shot causing the hesitation/stumble. But that particular design was used very early on by MC in these carbsbasically designing a foolproof, dependable mileage carb for medium sized I6s that still made good power when requested. Go under the hood and slowly work the throttle paying 100% attention to the accelerator pump over ride spring's nut, if you see the nut lift AT ALL from the accelerator pump arm it is compressing the over ride spring and not pushing the accelerator pump arm thus a lack of pump shot. the carb was bought new around 1990.