I have changer accelerator pump squirters and have changed the cam out. The accelerator pump puts a short burst of raw gas into the air stream. The ball lets fuel in, but is pushed back against its seat by pressure inside the pump when the throttle opens. The difference between some throttle bodies can be with the accelerator pump cams, which are not used in propane carburetors. We will install a Heli-Coil Thread Insert on your Carburetor with 7/8"-20 (7/8" diameter and 20 threads per inch) fuel inlet and reface the carburetors inlet gasket surface to ensure a leak free repair. The original accelerator pump diaphragm provides a 30cc shot. Some Holley. Although rarely necessary, the bigger pump can be installed on a 4150-style carb by using Holley’s conversion kit (PN 20-11). If the accelerator pump circuit doesn't work properly they must be corrected. and all of the squirters act properly. AED has combined every possible add-on feature and incorporated it into each of these Ultimate Performance carburetor kits to give you longer lasting and improved performance from your Holley carburetor. I found the Holley 94 social group. do NOT contact me with unsolicited services or offers. Portions have been sourced from various Holley documents. 02-09-04 05:51 AM - Post# 388767 what are the symptoms of an accelerator pump going bad. These keep the vacuum from pulling fuel out of them. Also to fix the accelerator pump do you have to tear the whole carb apart. I replaced the accelerator pump diaphragm and o-ring. An accelerator pump is a component on a carburetor. Add to Cart Compare. procedure when ever I build a Holley. The Advance Auto Parts core charge presented to you online today with your item is representative of the most common core charge. This car has an electric fuel pump. Several diaphrams, new pump, new bowl later and still it leaked. I've noticed that my intake had some fuel stains under the primary bowl, so I reached up. Each Holley power valve is stamped with a number to indicate its vacuum opening point. That also adds another place for oil to leak. Don't loose these! 18. Inlet system air leak. You can pump the throttle instead, and the accelerator pump will squirt extra gas to do the trick. Per your stumble, look at your accelerator pump linkage and make sure there is a tiny bit of preload on the pump arm at idle. Accelerator Pump Parts About Us. 00 ebay FMIC set. I spent a lot of time over the last 6 months on the phone with Holley regarding the leaking accelerater pump issue. A failed power valve could also cause the idle problem. I have changer accelerator pump squirters and have changed the cam out. The first accelerator pump adjustment is changing the hole on the arm that the rod goes through when moving the pump. A failed power valve could also cause the idle problem. One kit covers all Holley Spread bore Vacuum Secondary Carbs: 650 800 etc. The housing warped about 10 thousand! There are two ways to fix this common problem on the 735 holley. 3) Clean out the nozzle tip. So the moral may be check/clean and then double check/clean. 4) Replace the pump cup. On Dominator-style carbs, the pump capacity is 50 cc for ten strokes. How and Why to Adjust a Holley Carburetor Accelerator Pump Pump cams are replaceable, and as you can see, they can have two, three or even one hole. I've found it can take as much as. Holley also supplies a wide range of accelerator pump cam profiles that allow the pump discharge rate to be tailored to the engine. (c) This seems to imply that there can be a bit of throttle opening before the accelerator pump shoots a squirt of. Then, we installed the new (supplied) diaphragm from Holley. Your power valve hasn't even come into the picture yet. This pump MUST function properly for your engine to operate properly and the float level MUST be set accurately to enable the accelerator pump to function as intended. I still need some more, so I'm thinking that I need to switch to the hollow screw and the 50cc pump diaphragm. QUESTION My vehicle has a stumble from a dead stop. If nothing is coming out, check to see if the linkage is activating the accelerator pump on the carb. An accelerator pump is a small lever-operated diaphragm pump located on the underside of the fuel bowl that is connected to the throttle linkage. 1 has slight hesitation on acceleration. And i dont think the electric choke is adjustable. Although rarely necessary, the bigger pump can be installed on a 4150-style carb by using Holley's conversion kit (PN 20-11). one on each float bowl on either end of the carb. My second question. Why does my engine spit or backfire? First off, you need to determine whether it is backfiring out the exhaust or back up through the carb. Are you referring to the accelerator pump? For an exploded parts diagram, go to the New Holland parts web site by CLICKING HERE, and then pointing your mouse at "Parts & Service" up near the top of the page and then clicking on "Parts Search" from the menu that pops up. this of course meant no accelerator pump. I have a Holley 9022 800 CFM DP on my 454. I just put a 57 b intake and holley 390 cfm on my 55 with a stock 292 and A/T It had A intake with a 4v teapot before/ it sure rans alot better but I have a small stumble when I take off / so far I have check the float level,accelerator pump arm adj,move the pump cam to the #2 postion Im starting to think that maybe I need to replace the pump shooter which is a. the pump piston. If the accelerator pump circuit doesn't work properly they must be corrected. Order Carburetor Accelerator Pumps for your vehicle and pick it up in store—make your purchase, find a store near you, and get directions. Bottoming out an accelerator pump diaphragm can lead to a damage over time, or even rupture the diaphragm itself, which can cause a fuel leak, and the associated headaches which come along with that. 5 is a fail), not much better at idle she is running very rich, probably not just a fiddling with the idle air screw if it fails at 2500 rpm, which is set pretty lean now. Fuel usually enters the accelerator pump past a one-way steel check ball. I have a Rochester Quadrajet that recently started leak fuel all over the engine. Need some help - suggestions - direction to go been having issues with the edelbrock carb leaking so i rebuilt the Holley 4150 i had on the bench its a 4150 double pumper with a 750 body with no choke and i used Holley rebuild kit to do the job problem is it's idling around 2800 rpm ??. Vacuum leaks. Pull the metering blocks off and get some Jb Kwik and dab the holes shut. Accelerator Pump System. Air filter dirty or plugged 2. summit offers idle feed restrictions and accelerator pump discharge restrictors. You May also need to play with the accelerator pump cam to get a proper pump shot. Also while we are at it on the primary accelerator pump adjustment. Runs great now and am really happy with the throttle response for a big car. To counter that carbs incorporate an accelerator pump which gives a short burst of fuel to offset the additonal air and create a mix that can be burned. On Holley carburetors, the power valves can easily be blown out due to an engine backfire. Hg, "85" indicates 8. 2) Reset timing. Got the car running again recently and it was leaking at the primary accelerator pump. 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. You’ll need to also consider accelerator pump cams, high and low speed air bleeds, pump discharge nozzle, squirter size, accelerator pump diaphragm size, and power valves. Before installing the accelerator pump on an Edelbrock Performer Series carburetor into the main pump, fill the cavity half full with WD-40. Part# 120077. 2) Ignition timing retarded too far. Car runs pretty good every place other then off idle tip in. This can be caused from years of over tightening of the accelerator pump cover resulting in a warped cover. > Need help460 ford engine running a holley 750 is backfiring thru the casb > on accleration. Tuner worked on it but couldn't get it going. But the accelerator pump pressure simply pushes them up and allows fuel to squirt out when you mash the. Ford 351 Cleveland Engine Carburetion Guide Induction begins with a carburetor and there are a lot of them to consider these days because the market is competitive and plentiful. It is not as effective, but it is easier on your gas bill, and it forces less gas dilution in the oil (I have disconnected the choke on both my 440's). Bottoming out an accelerator pump diaphragm can lead to a damage over time, or even rupture the diaphragm itself, which can cause a fuel leak, and the associated headaches which come along with that. All Holley 4-barrel carburetors have a primary-side accelerator pump located on the driver's side of the primary fuel bowl. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. This is what that new Holley accelerator pump diaphragm looks like. when i give it more gas it clears up. We have a nice flat grinder that does a good job, but you could also use a good flat file. Hg, "85" indicates 8. My Mustang guru hammers it flat. You'll need to also consider accelerator pump cams, high and low speed air bleeds, pump discharge nozzle, squirter size, accelerator pump diaphragm size, and power valves. I have a Holley 750 on it now. At 7 inches of vacuum the 350 carb is really flowing about 430-440 cfm. Check for a large vacuum leak, like a plug left out of the manifold somewhere. NOW the pump shot will be instant. The fuel bowls are side hung with no external float adjust. The Holley type accelerator pump system consists of three main components: the pump diaphragm, the pump cam, and the pump nozzle (a. 350-500 rebuild kits feature: * Reusable Gaskets * Nylon reusable needle and seat gaskets. This is known as a wet pump system. I've tried everything and. The holley has really nice fuel bowls that are easy to adjust, don't evaporate, and don't maybe/sortof/don'tknow leak out of plugs. Find Holley Accelerator Pump Diaphragms 135-5 and get Free Shipping on Orders Over $99 at Summit Racing! Holley offers their accelerator pump diaphragms for all of their carburetors. How and Why to Adjust a Holley Carburetor Accelerator Pump Pump cams are replaceable, and as you can see, they can have two, three or even one hole. I have 2 cars with holley 4000 carbs. Buy this Holley 30CC Carburetor Accelerator Pump Diaphragm from CJ Pony Parts! This 30CC Carburetor Accelerator Pump Diaphragm will fit on 2-barrel and 4-barrel Holley carburetors. Live and learn. I had the exact same problem. 4180C Fuel Bowl Leak -- Can It Be Fixed? Can anyone tell me which accelerator pump cam they're using to avoid the all-too-common flat spot often experienced with. The diaphragm has a volume of 30cc and is not recommended for use with alcohol based fuels. This is the beginning of a very detailed question one of our readers asked the ATV AnswerMan. Fuel Throttle Sale. 4) Accelerator pump cup swollen up from contact with bad gas or chemicals. Nothing wrong with an Edelbrock. This has a 2bbl carb, and I'm seeing some fuel leaking out of the accelerator pump diaphragm (at the center where the shaft enters). The green material is the Viton rubber that is impervious to all those other nasty chemicals and will offer a much longer lifespan. Restricted fuel filter. The accelerator pump covers on both Holleys and 2100-2150s are usually over tightened by some PO. The accelerator pump is particularly vulnerable to vacuum leaks, backfires through the carburetor and dirty gasoline. The leak jet supplies fuel to the accelerator pump. Enrichener valve not seated or leaking. Accelerator pumps – in the good old days, accelerator pumps were made from leather. 3) Accelerator pump nozzle has dirt in it. Accelerator pump problems. Apparently the diaphragms used by Holley for the accelerator pump can start leaking when they are not very old. Unscrew the accelerator pumps, and carefully turn the carb over; two tiny needles will slide out of the accelerator pump bores. It will restart and idle. Just a dot on top of the hole and it will stay there for good. The saga continues. 3) Accelerator pump nozzle has dirt in it. Bottoming out an accelerator pump diaphragm can lead to a damage over time, or even rupture the diaphragm itself, which can cause a fuel leak, and the associated headaches which come along with that. Wiggle the arm up and down as you adjust it until the up and down goes away, then add one flat of the bolt head of preload. 3) Clean out the nozzle tip. We have a nice flat grinder that does a good job, but you could also use a good flat file. Replacement accelerator pump diaphragms for all Holley carbs. Vacuum leak somewhere, or hose off or hooked to wrong vacuum port. Ford replacement part covers D5AZ-9B559-A CM2092, C0AE-9B559-A,B,C; C2AZ-9B559-A. Newer gaskets are also coated to make it easier to remove a fuel bowl if necessary without tearing the gasket. Second the electric pump idea. 1932; Air Fuel; Transmission; Steering. Inlet system air leak. I thought Holley made poor design choices when so many gaskets are on a vertical plane whereas the Carter's gaskets were on a horizontal plane where they were much less susceptible to leaking, and the accelerator pump diaphragms were pretty flimsy in the Holley's as well, leading to engine compartment fires when they started giving way, leaking. Today I'm going to take a couple of moments to talk about how to properly adjust the accelerator pump arm on a Holley carburetor. This pushes additional gas into the throat of the carburetor. Problems with 350 Holley - posted in Engine: Gday all Ive just fitted a 350 holley to my 253 and it doesnt run properly. Check your timing. The Holley 82750, does not have secondary idle mixture screws. Then, we installed the new (supplied) diaphragm from Holley. In more serious cases of accelerator pump failure, rapidly pressing on the gas may cause the engine to stall, again due to the lean condition that can be created when the accelerator pump is not working. If the accelerator pump is in good condition, the problem may be with a choke that either will not close because it is caught on something, or because the choke linkage requires lubrication. accelerator pump leak Bronco Tech Community Message Forum Photo Gallery Event Calendar Book Reviews Bronco Wallpaper Bronco FAQ Link Back to CB! 600+ Bronco Links!. This is also the solution to the Holley 2bbl on 360s which leak through the float bowl to throttle body gasket. They are located in the center of the block that feed the accelerator passage (you can see right thru the block). If you have a vacuum secondary carb, the kit comes with a new secondary diaphragm, seal, and spring. 015˝ of clearance to exist between the pump spring adjusting screw and the pump diaphragm arm at WOT. Using a small Philips head screwdriver, we removed the pump housing (careful to not lose the spring). Get Yours Today! We know our parts and products. I'm still struggling with this Holley TA 470. In my 1992 Chevy Silverado, 5. Getting a slight hesitation out of the hole at wot. Portions have been sourced from various Holley documents. I wish I had seen the posts about fuel line fittings before I ventured into this. I need to replace a leaking accelerator pump diaphragm on a 1982 Ford Motorcraft Model 2150 carburetor. The accelerator pump is particularly vulnerable to vacuum leaks, backfires through the carburetor and dirty gasoline. When examining a valve there will be no evidence that it leaked. Carter P4070 In-Line Electric Fuel Pump. Holley 135-5 Rubber Accelerator Pump Diaphragm Volume measures 30cc Made of rubber material Does not include screws Not for use with alcohol base fuels Fits. I noticed that the 1094 Lincoln Teapot sitting on the dyno mule still pumped fuel from the accelerator pump nozzles one week after it. If you have any questions, please call 1-877-ADVANCE (238-2623) or visit any Advance Auto Parts store. screw down the carb air horn with the two center screws. The Holley type accelerator pump system consists of three main components: the pump diaphragm, the pump cam, and the pump nozzle (a. Switch on and wait until you hear the pump stop before attempting to start. Ok guys, sorry to bore you with another jetting question, but I have read, watched, searched and listened to helpful friends and I am still no further ahead. Apply epoxy to main body casting plug to eliminate common "leak down" problem associated with Quadrajets. Don't loose these! 18. A failed power valve could also cause the idle problem. STOP HERE and turn the carb over. The original accelerator pump diaphragm provides a 30cc shot. I think the fan is blowing it around. Is the timing correct?. They are made from the finest materials for long life and a leak proof seal. For example, my setup works best with a blue pump cam mounted in the #2 screw position. 350 Holley, 202 Tuning - posted in Engine: Hey guys, we usually only do EFI tuning at work and mainly common rail diesels for that matter. Notes: Will not work with accelerator pump transfer tube. Test with Holley hand vacuum pump. It looked like a brand new pump. Accelerator Pump. Solution #3: If you're running an aftermarket fuel pump, make sure the fuel pressure isn't set too high. Apparently the diaphragms used by Holley for the accelerator pump can start leaking when they are not very old. Champion Carburetor 64-73 Autolite & Motorcraft 2100/4100 Series Carburetor Accelerator Pump [CAG-WLK-64-279P / C4AZ-9B559-A] - This Diaphragm Pump mounts on the front all 64-73 Autolite 2V carburetors as well as 64-67 Autolite 4V Carburetors. But my business partner has a HT Monaro with a 350 holley and pretty much stock 202 Red bar extractors, exhaust, electronic dizzy and of course the Holley. If not, then the carb may have an internal leak that is allowing gasoline to drain out of the float bowl. Gas leaking from accelerator pump I thought it was a vacuum leak, but couldn't find one. If nothing is coming out, check to see if the linkage is activating the accelerator pump on the carb. The original accelerator pump diaphragm provides a 30cc shot. Holley remains the carburetor of choice but there are nice alternatives from Demon, Edelbrock, Summit Racing, Quick Fuel, and Proform. Great Holley rebuild kit that has the newer gaskets and accelerator pump for the nasty gas with a percentage of ethanol in it. When you shower down on the accelerator hard from idle speedthe motor nearly dies or backfires through the intake and then catches up. Accelerator pumps - in the good old days, accelerator pumps were made from leather. A failed power valve could also cause the idle problem. I've found a couple of part numbers for this diaphragm but nothing that my local parts jobber can cross-reference. Champion Carburetor 64-73 Autolite & Motorcraft 2100/4100 Series Carburetor Accelerator Pump [CAG-WLK-64-279P / C4AZ-9B559-A] - This Diaphragm Pump mounts on the front all 64-73 Autolite 2V carburetors as well as 64-67 Autolite 4V Carburetors. Match it with the gasket from your carburetor kit. Just my opinion of course. Another common place for a fuel leak to develop is in the rubber hose and metal tube that leads from the tank to the fuel pump. So it has been running trouble free till now. Take a close look at accelerator pump arm that should be in contact with the adjustable accelerator pump cam. accelerator pump leak Bronco Tech Community Message Forum Photo Gallery Event Calendar Book Reviews Bronco Wallpaper Bronco FAQ Link Back to CB! 600+ Bronco Links!. I pulled the float and held it under water, no leaking. The problem arises because the pump, though it may deliver adequate pressure at idle, cannot hold that pressure when the engine demands more fuel. Holley float bowls are often bent and leak. I did have a vacuum leak at the base of the carb. Accelerator Pump There were a multitude of different accelerator pumps used on the 4GC carburetor. , (Also available separately: Spread Bore Double Pumper Carb rebuild kit, AED 4165). Check the timing with a light, that's a must. 3) Accelerator pump nozzle has dirt in it. Accelerator Pump System. Since the metal tube is exposed to the elements, it's not uncommon for it to become rusted through to the point that the fuel is leaking out. Noticed it came stock with a dark green accelerator pump cam. As mentioned, new rebuild kits contain floats and rubbery bits that can tolerate ethanol, but the old pot metal carb bodies sometimes cannot. turned out the pot metal casting of the metering block had broken away, and let a plug and check ball fall into the main bowl. Lots of good info there. Holley accelerator pump diaphragm. I don't like carb work, don't know much about them. Holley 108832 Blue Fuel Bowl Gasket - Pack of 2 Holley 135-10 GFLT Accelerator Pump Diaphragm worn-out gaskets that may cause a leak and allows fuel line. Is your float still afloat? Popping out the exhaust: Incorrect Jetting. Some fuel pumps pulsate and this can cause a problem. and all of the squirters act properly. I had a minor leak from the accelerator pump and thought it would be a good idea to get it rebuilt, rather than just replace the accelerator pump (see earlier discussions). I noticed that the 1094 Lincoln Teapot sitting on the dyno mule still pumped fuel from the accelerator pump nozzles one week after it. Which type of discharge nozzle do you use in your Holley? I have a lean condition off idle when cracking open the throttle, and know I need to increase my discharge nozzles. Got the car running again recently and it was leaking at the primary accelerator pump. This is also the solution to the Holley 2bbl on 360s which leak through the float bowl to throttle body gasket. These quality pieces ensure that the job is done right and help to keep your carb functioning like new. Leaking accelerator pump diaphragm Autolite 1100 Accelerator Pump and How It Works - Duration: 2:49. i know its not a vacum leak. The fuel is not draining out the accelerator pump ckts. Also make sure sure the bullet is in the accelerator pump well and the pump check valve is doing it's job. Dave, probably the worst enemy of Holleys is to sit unused for any longer length of time,particularly with modern fuel brews. This carby has been on the car before , it started to play up so I put the stromberg back on. As the throttle lever is moved. The original fuel pump diaphragms on Holley carbs are made of rubber and I wasn't certain whether that rubber was the kind that could be damaged by the ethanol (ethyl alcohol) that's now in modern gasolines. This accelerator pump diaphragm is used to replace the existing worn-out one part is usually underneath the front of the carburetor. The power valve and accelerator pump were fine. QUESTION My vehicle has a stumble from a dead stop. pump diaphram are not wide enough and I could not get them to stop leaking fuel after install. These metering block gaskets from Holley are available for a variety of carburetors with intermediate systems. 1/32nd of an inch can make all the difference in the world when setting some of them up. Vacuum leaks. 5 is a fail), not much better at idle she is running very rich, probably not just a fiddling with the idle air screw if it fails at 2500 rpm, which is set pretty lean now. My Mustang guru hammers it flat. Bottoming out an accelerator pump diaphragm can lead to a damage over time, or even rupture the diaphragm itself, which can cause a fuel leak, and the associated headaches which come along with that. Holley accelerator pump leak ?'s I have ironed out all the other issues and the car runs fine except for one issue. Had this problem with a holley, the check ball for the accelerator pump had froze in place by a bit of corrosion. First verify you're getting a good shot. If nothing is coming out, check to see if the linkage is activating the accelerator pump on the carb. On the holley, it was fuel metering. The power valve cover is often bent the same way on the 2100,2150, and 4100s. Your order may be eligible for Ship to Home, and shipping is free on all online orders of $35. Also make sure sure the bullet is in the accelerator pump well and the pump check valve is doing it's job. I've been increasing my primary accelerator pump discharge nozzle size, and I'm at a 35. I had the exact same problem. Sold 1/pkg unless otherwise noted. The previous owner had it jetted very rich but it still bogged like it had a bad accelerator pump. Then, we installed the new (supplied) diaphragm from Holley. The accelerator-pump installs fairly quickly. He is going to buy a new carb. This gives an enriched air flow into the engine causing acceleration. It looks like Dicks Hotrod Carbs is the best place for parts. In addition to wiring harnesses, PSI carries Holley Products, Vintage Air A/C, Dakota Digital Gauges, HPTuners and PCM programming, Fuel Pump Kits, Engine Sensors, Extension Harnesses, Replacement GM connector pigtails and a complete line of hardware to complete your conversion needs!. When the pump tried to draw fuel through it, the pump would suck air through the crack. Also to fix the accelerator pump do you have to tear the whole carb apart. The throttle plates have to move a certain distance before the lever arm contacts the plunger. Place it on the base and mate the base to the float bowl. I have a chart (from the Holley carburetors book by dave emanuel. As with most domestically produced carburetors, a 4150 Holley has a choke, float, idle, off-idle, accelerator pump, air bleed, main metering and power-enrichment metering circuits. You may need to change jetting, power valves, accelerator pump nozzles, etc, but its more likely you just have a fuel pressure problem. AED 4150 Carburetor Rebuild Kit. finally got it to stay running but not that great. How and Why to Adjust a Holley Carburetor Accelerator Pump Pump cams are replaceable, and as you can see, they can have two, three or even one hole. Only the highest quality components made. But my business partner has a HT Monaro with a 350 holley and pretty much stock 202 Red bar extractors, exhaust, electronic dizzy and of course the Holley. On Dominator-style carbs, the pump capacity is 50 cc for ten strokes. Only the highest quality components made. Holley float bowls are often bent and leak. 1) Vacuum leak. The Zako-ATS 3/8" Throttle Shaft Repair Kit. If security is a huge concern for you, don’t worry—our transactions are VeriSign-certified to make sure that every purchase is safe from online thieves. it's just out of adjustment, C. Also while we are at it on the primary accelerator pump adjustment. There ought to be zero clearance or a slight preload on the linkage arm to the accelerator pump lever. do NOT contact me with unsolicited services or offers. A faulty accelerator pump will typically produce a noticeable effect on the engine performance when it fails or is having a problem. Get the LIST number off the air horn on the carburetor and get a rebuild kit for it. Secondaries opening too soon Lack of power, Sluggish, or Spongy 1. Hg or below. Install the accelerator pump squirter. Buy this Holley 30CC Carburetor Accelerator Pump Diaphragm from CJ Pony Parts! This 30CC Carburetor Accelerator Pump Diaphragm will fit on 2-barrel and 4-barrel Holley carburetors. It never leaked because the lines and valve are under negative pressure. Portions have been sourced from various Holley documents. Third, suggest replacing gaskets, power valve, and accelerator pump diaphragm. shoot some carb cleaner or starting fluid around the edges of the intake and see if the RPMs come up from sucking it in around the edges of the intake. 60 valves, Crane roller rockers, Edelbrock Performer RPM intake, a Holley 650 cfm double pumper, and auto transmission. Save on every Holley Carburetor Accelerator Pump in Canada when you shop at AutoPartsWAY. Ive got a 4bbl carter 625cfm. When you rev the engine, there should be a spray from the accelerator pump into the venturi, but there should be no liquid fuel and definitely none leaking outside the carb. Re: Holley Accelerator Pump Diaphragm. These quality pieces ensure that the job is done right and help to keep your carb functioning like new. SuperScamp: You're right, the '64 and later Holley 1920 accelerator pump is a spring-driven design. If the accelerator pump diaphragm is damaged, then it'll leak. It looks like Dicks Hotrod Carbs is the best place for parts. For many model 2100 and 2150 Autolite and Motorcraft carburetors. Length of stem is 7/8″. Holley has a tuning procedure (by vacuum) on the company site, and the Holley valves are marked with a value (vacuum that they close at). Some fuel pumps pulsate and this can cause a problem. I havnt checked accelerator pump measurements yet or the nylon fast idle cam behind the electric choke yet. I was able to find a new Holley diaphragm at Advance Auto for about $3 and it was an easy repair. they said it would be fine with my 780 vacuum secondary Holley.