Holley carb backfire through exhaust. Issue I have is when the engine is at higher RPM, above 3000 then let off the gas there will be a popping sound out the exhaust. 4. Put it back together and now it runs really poorly with backfiring through the throttle body. Sep 2, 2018 · From there you can retard and advance from zero. and idle rpms. Backfires out the Sniper May 16, 2021 · Hey, I'm looking for some tips after rebuilding my holley double pumper. Any help would be great. Jun 4, 2014 · C3 Tech/Performance - backfire through new 600 holley - Good afternoon all Got a 283 automatic, put on new 1106 Edelbrock, 600 Holley, cap, wires, plugs, coil ect. Fix your choke so it works properly. You may find this useful reading: Tuning Holley Double Pumpers (Part 2) - Auto Enthusiast Aug 30, 2016 · C3 Tech/Performance - Afterfire/ popping exhaust. Troubleshooting - backfire through carburetor Holley 169K subscribers Subscribe Subscribed Aug 26, 2007 · It isnt an annoying carb backfire, it wont run. I have read so much on the internet and watched enough videos to make my head spin, but nothing is telling me what Jan 20, 2014 · Small Block V8 (221, 260, 289, 5. I adjusted the idle air mix screws. Chicago is well digger butt cold at the moment. Jan 25, 2011 · It is an '85 . Dual plane intake?? A problem in one side of the idle circuit can give a pop only in every other cylinder occasionally in the firing order. If you get a pop “backfire” out the exhaust pipe, the plug is firing when the exhaust valve is open. When you hear a backfire, you need to determine whether it is backfiring out the exhaust or back up through the carb. My setup is a basic holley 600 cfm, with only a front metering block, on a cast iron 4 barrel manifold. Inline 6 with a single barrel holley 1963 international half ton Jan 11, 2016 · I have 283 sbc fresh rebuild that stumbles and backfires on acceleration. I know it can be a timing problem but what else ? It did it when I had the 2 barrel carburetor (and at that time the car seemed properly tuned), now I have a Holley 4 barrel and it's the same. Hope any of this helps. Why #7 is not fully closed could be caused by several reasons, bent valve, burned valve, burned seat, sticking valve, broken or weak valve spring, are a few. Jul 31, 2022 · I can't figure out what's happening with my sbc 350. 8/351W) - 351w: backfire: timing or something else? - I just installed a wieand intake manifold and holly street avenger carb on my 78f100 with swapped in 86 351w. So the factory timing chain is 4 degrees retarted? The cam is cut straight up and down, in other words it's cut at zero. Had mechanic try to diagnose the Jan 9, 2011 · I took the old Edelbrock carb, and put that back on, to see if it would run good, as I had it running nice with that carb before I started working on it, and it ran WORSE ! I put the Holley back on, and fired it up, not only was it backfiring through the carb, but it started backfiring through the exhaust too! Sep 11, 2025 · Holley carburetor troubleshooting explained. Vacuum advance pulls another 15 or so, on the manifold. . Aug 21, 2023 · The backfiring through the intake points to a timing issue (like what happens when you have a regular distributor 180° out), but I can't for the life of me figure out what I did wrong. When you accelerate slowly runs smooth when you accelerate quickly backfires through Oct 11, 2004 · The intake or carb? if the carb then which nipple? i don;t want to play guessing games if at all possible. secondaries on a stock 305. Nov 23, 2012 · If you let today's gas sit in your carburetor for 3 or 4 months without Sta-Bil or a similar fuel treatment, the gas will have started to gel and clog your idle circuits. I haven't had it backfire when revving it at idle, which lead me to think that it was a timing issue rather than a fuel issue. But it was running, then had a wire fire, so that would lead me back to ignition. I'm having issues with backfires through the throttle body. I put a new Holley Avenger 670 on and shortly after developed a backfire through carb at WOT. Sep 1, 2005 · Backfire is a sure sign of a lean condition. Dec 2, 2009 · Troubleshooting - backfire through carburetor Bill Tichenor 12/02/2009 10 min read Jun 22, 2023 · I have a situation re: carb stumble and backfire under acceleration. (1700-2500 RPM). The engine is a Chevy 350 with a Holley that is not the original engine or carb in Jan 14, 2005 · Ok, here's the situation: I just rebuilt the carb on my truck and now every time I punch the throttle or even just give it more than half throttle the engine backfires through the exhaust. If the bowl is going dry, that would explain it. May 28, 2016 · Reaching out for some help with a puzzling backfire in my 71 Mach I 351c. Apr 23, 2024 · For backfiring through the carb to occur it indicates #7 intake valve is not fully closed when air fuel mixture is ignited while the exhaust valve is still closed. Ever since i have Mar 20, 2005 · Small Block V8 (221, 260, 289, 5. -Jeff Oct 8, 2020 · Is this a backfire "cough" in the intake manifold? Camshaft gong flat will give that symptom if it is an exhaust lobe. Has 60 psi fuel pressure, IAC Position 5% at idle. ” This occurrence refers to the combustion of fuel and air mixture within the intake manifold or carburetor, resulting in a loud bang that reverberates through the engine and exhaust system. It Sniper EFI Tuning & TechI mounted the WBO2 sensor about 2" behind the header collector as per the instructions. It was worse going down the hill, but also did is randomly on level ground. 0L and a 4L60E transmission controlled by Terminator X Max EFI. I called the carb place that rebuilt it, and they said it must be an electrical or ignition problem as a backfiring problem is 99% electrical. i still have the old springs, valves, and retainers in the valvetrain everything else is Feb 18, 2008 · I'm getting a backfire through the carb under acceleration (part throttle or WOT) off idle. Jun 3, 2013 · Trying to get the motor started for the first time and I am getting large puffs of fire out of the top of the carb, some times the residual fuel sitting in the carb will burn off. If you would like to help support the channel you can do so by Apr 6, 2014 · Symptom - Backfires or Pops through exhaust Lower float level Decrease fuel pressure Decrease jet size Readjust butterfly position, primary & secondary Apr 4, 2021 · Just a thought here, but most all of the backfire & popping through the throttle body problems end up being mechanical issues and not Sniper issues. SBC 283 with 4 Holley 94. (through the carb) Then I change the plug and wires and shes good for another 4-6 months before it happens again. Also, when the engine is floored with the accelerator pedal, the engine dies unless you let up right away on the gas. Mechanical is working and goes all in by 3000 rpm. It'll backfire through the exhaust, but mostly the carburetor. Under load it backfires through the intake. Has 18 inches of vacuum at idle Stock internals bored over . What do you suggest to Sep 3, 2011 · Its backfire through the carb as a result of insufficient atomized fuel reaching the combustion chamber when the throttle is blipped and the vacuum signal drops under load. What causes backfire through the exhaust at idle, and how do you fix this problem? Read on for detailed explanations of possible causes and how to store Feb 27, 2018 · Hello everyone, I just got my rebuilt SBC 400 installed in my 56. A couple Some people describe, popping out the exhaust as back firing. $1300 later and still has the issue. If I press the gas gradually, there's no issues and it revs as expected. Accelerator pumps good, adjusted properly. Nov 30, 2015 · Popping back through the carb (as opposed to an ignition back fire) is the result of running lean (more air than fuel). To avoid filling your crankcase with unburned fuel, remove the fuel pump relay before you attempt any more starts. 5. will idle fine, and in park or neutral you can rev and it is fine. Look for each rocker to be moving about the same amount. Even in park, if you mash the gas the car will almost stall out, then POP!, then if you let off the gas it will come back to life. It would be fairly obvious while watching the rockers go through the motions while bumping the engine over with the starter. I'm having some issues with the carb though. Apr 14, 2021 · Sniper EFI Tuning & TechNo data flashes and yet to have a good start. Runs great until you floor it and it will backfire and pop through throttle body. Let us know what you determine. However, since individuals who have little experience with engine tuning and modification do most installations, this information is provided so that Jan 22, 2014 · 3. Sep 8, 2014 · It was backfiring through the exhaust - I'm 99% sure. It occurs mainly when under a slight load/acceleration. May 24, 2025 · An engine backfiring through the carburetor is a sign of malfunction, often related to the fuel-air mixture, ignition timing, or exhaust system. It has ported 882 heads that are freshly decked with new valve guides, valves and springs, new cam and lifters and new intake with a Holley 675 carb. With the relay out you can still verify your timing. Power valves were changed to 1/2 of idle vacuum. The exploding mixture then vents through the carburetor. Timing at 12. I've had 3 or 4 different holley carbs on this motor, and every single one has this problem. Apr 29, 2019 · Now getting a backfire through the carb (seems to always be the one over the 5/7 cylinders) on acceleration. I used a Shop-Vac to test for exhaust leaks by pressurizing the exhaust and sprayed soapy water, so I found several small bubbles around the WBO2 clamp on bung and a few just after the header collector. I Jul 31, 2018 · My problem is that I get a backfire when I push the pedal down more than about half way at once. :yes: Nov 30, 2019 · If the motor fires right up, idles and revs but backfires through the carb (and you have ruled out bad wires, wires installed incorrectly, bad distributer cap or timing out of wack) you could have a bad/worn intake valve. the hei w/ holley dp is a pretty well known set up, if someone can help me out maybe this will solve the backfires through the exhaust? THANKS. Sep 23, 2015 · I have a new (rebuilt) 302 with a holly carb that barely runs. Wires are correct. When I let off the throttle and the engine is slowing the car down (4 speed manual), I'm getting an exhaust backfire. (Backfires out the carb when too retarded, backfires out the exhaust when advanced. The engine throws black Jan 14, 2009 · The carb will make the big power sound (woooo) but you won't be going anywhere. Feb 20, 2015 · If you get a steady rhythmic pop out of the carburetor that changes with engine RPM, you have an exhaust valve not opening and it is still firing on that cylinder, but blowing the exhaust back up through the intake and carburetor. Jul 4, 2025 · Do you hear a loud pop through the carburetor? Learn the real causes of carb backfire and how to fix them fast with easy steps anyone can follow. But if I blip the Jul 29, 2007 · OK I am almost finished with the project. So if I advance the cam it should clear up my problems. took the electric choke off an Avenger Feb 25, 2007 · My rebuilt 351c has started backfiring thru the exhaust and sometimes the carb. Does it if you rev in idle or decelerating. Best advice: drain tank and lines and rebuild/clean the carburetor, paying particular attention to blowing out all the tiny orifices with compressed air and carburetor cleaner. Jul 21, 2015 · C3 Tech/Performance - Holley carb 3310 750 cfm hesitation on idle backfire - installed a rebuilt Holley 750 CFM 3310 carburetor the other day. At that point, you need to remove the valve covers and report back. We get a backfire through the carb if you open the throttle quickly. Could the plug wires be cross Dec 2, 2014 · Firing order is right. Oct 12, 2022 · Learn about Holley carburetors troubleshooting where everything from basic troubleshooting tips to advanced diagnostics and tuning procedures are discussed in great detail. 0/302, 5. ) Problem gets worse as engine warms up. Clean the air bleeds and idle passages with carb spray, including removal, spray out, and replace the idle mixture screws and see if it Dec 2, 2012 · Hey guys, I'm trying to tune up a carb ffor a buddy of mine, it's a Holley truck avenger 670 on a chevy 350 in a jeep with 44 boggers. 8/351W) - 302 backfire through exhaust - So i just got done rewiring and replanting all of my ignition parts because i was having trouble with my motor cutting off. It's much more intense when coming off of hard acceleration. Oct 28, 2005 · 440 backfiring Performance TalkClick here to search for Mopar cars and parts for sale. Even verified the firing order by removing the valve covers. I need advice on carb settings. It doesn't backfire through exhaust. Pretty sure the timing is at least close and firing order is correct. The engine becomes less efficient, and the popping sounds can be irritating. Oct 20, 2022 · Discover the answer to your burning what causes backfiring through the exhaust question with our in-depth guide. I'm not sure if there's something I need to adjust in the tune Jul 8, 2019 · Sent unit to holley they said tested fine. Any help of how to fix issue would be great. Its a holley 850 DP with mechanical secondaries. Could possibly be a stuck valve. Which wire do I need to separate, right now they run together through the firewall. 318, 2WD holley 2bbl. All recently rebuilt. :yes: For all Holley Automotive Superchargers This material is not intended to replace your installation instructions. Everything was working well before I installed the repaired Digital 6. 350, 600 Edelbrock, Standard dist with Petronics HEI module. This information is provided as a helpful supplement. 20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud. Initial timing set at 12 May 22, 2013 · Hack-The carb sat for about a month total, I did try my holley 700cfm with the exact same result. We usually refer to an exhaust backfire as a "backfire", and backfiring through the carb as "spitting" or "coughing". I have just replaced the intake and exhaust gaskets, plugs are good, readjusted the Edelbrock carb idle with a vacuum gage, moved the timing around a bit with no change. I have exhaust backfire when I have heavy acceleration. Understanding these causes is pivotal for maintaining your vehicle’s health and performance. Everything was OK during the installation and bolts were torqued to 9 Nm, as Holley recommends. Something in the setup is causing a serious problem. But if your in neutral and start revving it, around 2000 rpm it starts popping out the carb. com 73-87 Chevy _ GMC Trucks Engine/Drivetrain Backfire Feb 25, 2007 · My rebuilt 351c has started backfiring thru the exhaust and sometimes the carb. Carb is a Holley 750 vac. Thanks. There is also a noticable power loss. Oct 8, 2020 · Is this a backfire "cough" in the intake manifold? Camshaft gong flat will give that symptom if it is an exhaust lobe. Dec 2, 2009 · Troubleshooting - backfire through carburetor Bill Tichenor 12/02/2009 10 min read Jan 14, 2005 · Ok, here's the situation: I just rebuilt the carb on my truck and now every time I punch the throttle or even just give it more than half throttle the engine backfires through the exhaust. I have not adjusted anything on the tune. Timing was set to 10 initial. Improper carburetor adjustments or vacuum leaks can cause this condition. It had an edelbrock on before the Holley that didn't pop like this so it's not the motor itself. Anyone have any ideas where to check next? Can this happen as part of the learn process? Sep 29, 2018 · It starts to backfire through the carb when I get on it at all and above 3000 rpm. 30 Holley 600 carb, Holley intake, headers. Popping/backfiring thru the carb = possible bad intake valve / weak spring I'm just in the initial driving phase of my Terminator install. I then upgraded the battery and now the no data issues appear to be gone but under acceleration it pops out the exhaust. Could the plug wires be cross May 28, 2016 · Reaching out for some help with a puzzling backfire in my 71 Mach I 351c. Lean or rich condition? - I just replaced the carb with a New Holley 0-80457SA 600CFM Aluminium. Nov 29, 2019 · This allows the explosion to travel back out the cylinder through the intake valve and out to the carb. No fire just fuel. Thoughts? Also from my understanding fire out of the carb was too advanced timing to too early. Car is running great, idle quality is good. Starts right up and runs smooth. It ran nice for about a week. Seems like a lean condition? It Won't backfire if you May 16, 2021 · Hey, I'm looking for some tips after rebuilding my holley double pumper. What causes backfire through the exhaust at idle, and how do you fix this problem? Read on for detailed explanations of possible causes and how to store Sep 27, 2022 · A backfiring car experiences a sudden loss of power and poor mileage per gallon. I've messed around with it quite a bit with little progress. I had my face over the carb to see what it looked like, and I saw a backfire through the carb right at the stumble. I Nov 29, 2021 · This morning i go to start my truck and it turns over but wont start. This is a common problem with double pumper carbs that can force all four barrels open by stomping on the gas. The car is a '89 Mustang 302 with H/C/I. Idles nice, engine revs nice but on start up (cold or warm) the engine backfires out of the carb. Mar 27, 2023 · I have a SBC 427ci was running fine, probably five miles on it, maybe a couple hours of idle time. You can take the valve covers off one side at a time and watch the valve action while it is running. Had mechanic try to diagnose the problem. Fuel delivery problem with the carb as stated with the choke for example. Aug 13, 2011 · Since I have my Mustang I always get backfire in the exhaust when decelerating. On the highway, it occasionally pops through the carb, or through the exhaust. Does it idle rough like it has a miss. Any suggestions? Thanks is advance. I know this is caused by a lean condition but can anyone explain to me physically what is happening? I know it is combustion, but where and how? Oct 10, 2019 · First off, you need to determine whether it is backfiring out the exhaust or back up through the carb. Runs great while in park but under a load on the street it sputters and backfires. I still have one small issue. Ignition can be set Sep 22, 2006 · A stuck valve (non-operational valve) can cause backfire thru carb. So, it seems to me that I either have an ignition problem or a carburetor problem Any and all assistance would be greatly appreciated! Apr 19, 2020 · I have a 6. We're trying to tune it and set the idle. Ask your carb rebuilder if there was, or if he installed an anti-backfire check ball to save your power valve from backfires through the carb. Then put 'er in drive and go, she backfires and loses major power. Apr 16, 2025 · If a rich enough mixture to cause backfiring, I would expect to see carbon on the plugs. Right after starting the engine, I realize that I have afterfire/popping in Idles but backfires and dies when you try to get giddy up and go. Aug 16, 2013 · I noticed after the car warmed up and on the way home, the car would pop and backfire though the exhaust on deceleration. timed it by ear cause light broke. Could be my issue here. Some later holleys have a check ball in the base plate to protect the power valve from a back fire. That said, carb needs tuned on vehicle to account for the various engine components. the engine starts up pretty decent,and idles very smooth. Any help would be Feb 7, 2024 · Before we delve into the heart of the matter, let’s first understand what exactly we mean by “engine backfire through the intake. Apr 18, 2015 · Usually backfiring through the carb is either timing or an open intake valve when the engine fires. I had a lot of very knowledgeable and experienced guys trying to help me, and nobody could figure out what it was until I ran that compression test. We took the intake off because there was an oil leak at the china rail. After a couple tries it backfires through the carb (Holley sniper efi). My question is will this thing still run with an "open" module and could that be the cause of my issue? Jan 22, 2014 · 3. Mar 5, 2013 · Backfire thru carb is usually timing. It Sep 21, 2006 · Hi- I posted over in engines and didn't be much responce, So I thought I would post over here for some attention from the holley gurus :) I have a holley 750 vacum Secondary carb that Backfires through carb with a blip of the throttle. Have yet to get a good running condition with my Sniper setup. Feb 14, 2022 · 350, in the 55 - last year - started to backfire thru the carb when I would get into it - well after complete tne up, changed carb from edelbrock to holley, complete new distributor, all new wires, plugs, played with timing it still wants to backfire thru the carb - not all the time but you Dec 2, 2014 · Firing order is right. Not a backfire. On throttle no issues and runs normal. Clean the air bleeds and idle passages with carb spray, including removal, spray out, and replace the idle mixture screws and see if it Sep 27, 2022 · A backfiring car experiences a sudden loss of power and poor mileage per gallon. Jul 2, 2008 · I've been having some problems with my 1 year old Holley Street Avenger Carb on my 383. Vacuum advance. Drivetrain specs as follows: 87 truck 460 Weiand Stealth May 26, 2011 · If you have backfires in both the carb and exhaust, sounds like the plug wires are mixed up. He put on a new electronic module, plugs, wires, dizzy, and Nov 23, 2022 · In this article, we will discuss the possible causes of the carb backfire problem and the solutions you can apply to avert a potential disaster. when I mash the gas from idle it will hesitate and backfire out the carburetor. For these reasons, you should fix the problem to restore the condition of your car. Jun 22, 2023 · It turned out all of the exhaust seats were hammered out of both heads, and I had almost zero close pressure as a result on all exhaust valves. Blipping the throttle causes a major carb backfire. We've taken the distributor out and rephased it multiple times, Nov 6, 2022 · I'm working on a 1986 Dodge Ramcharger with a 318. If I ease into the throttle or maybe roll into it quickly but smoothly, it runs just fine. It starts and runs great but every now in then it will backfire and die. But unfortunately my gas station quit selling non ethanol gas. Holley Superchargers are designed for trouble-free installation and operation. It also fas a tad bit of hesitation off idle. I think it is popping back through the carb or intake. Had engine start & idle, then shut it off only to not be able to get it started again. A blown power valve shouldn't affect idle, unless the backfire damaged something else. 1 turn out on all 4 seems to give the best response. poppy- the compression does seem low to me too, motor was warm and carb open with a screw in guage with all spark plugs out, the pistons and rings were put in about 10 years ago going for 10:1. Mar 2, 2012 · Sorry I keep posting questions but I'm a newb. the problem I am having is that it is backfiring Mar 23, 2003 · I get numerous afterfires through the exhaust and more backfires through the carb, this usually starts happening after running the car for about 15-20 minutes on the street. Usually this problem occurrs with and oversized carb for the motor, but 650 is a good match. The engine runs well 80% of the time, and I've checked for vaccuum leaks using a propane torch. As mentioned if an exhaust lobe wiped carb backfires can happen. My question is with the exhaust pressurized will those small leaks matter and Mar 29, 2006 · The engine still stumbles and backfires through the carb. What could I be overlooking or not doing? Is the Digital 6 causing this problem? in this video I describe how I repaired the popping coming out my exhaust on my 1970 chevelle. The engine backfires terribly through carb and even catches Fire in the carb. Bought the car and have papers showing a new engine build and heads from previous owner. Tags:None Danny Cabral Administrator Join Date:Dec 2009 Posts:39325 Share Tweet #2 04-19-2020, 09:47 AM Overlay the datalog onto your Config File, and pay special Jul 3, 2020 · Car idles and drives great right now. Mar 27, 2004 · We're working on a 350 SBC, we just finished putting a Holley street dominator manifold, lunati cam, and Holley 4160 750 CFM carb. Inline 6 with a single barrel holley 1963 international half ton Idles but backfires and dies when you try to get giddy up and go. Learn quick checks, repair tips, and tuning methods to prevent stalling and poor mileage. The engine has a small backfire or pop coming from the exhaust at idle, Other than that engine runs good. Never the less, it would be worthwhile to check Oct 15, 2001 · A backfire through the carb, is, technically , I believe, called a popback instead of a backfire. Sep 30, 2021 · A backfire during an attempted start also sounds like timing. May 1, 2010 · Wiped exhaust lobes will cause backfiring through the carb. Also to know is, what causes an engine to backfire through the carburetor? Fuel To Air Mixture Is Too Lean Too much air and not enough fuel causes backfires to occur in the intake manifold. When a holley back-fires it often blows the power valves. Keep in mind, you also may have a double whammie, esp if you have a Holley carb. Checked timing msd box with locked out pro billet and the timing is spot on. Allowing the explosion out through the exhaust valve and to the muffler/exhaust pipe. Tried advancing and retarding by hand, too, and it goes from one extreme to another. And everything seems fine with the exception of a backfire out through the carb on start up. Intake valves are still open letting the combustion come up through the intake and out the carb? Too retarded and it will backfire out the exhaust but of course through the exhaust valves? Mar 30, 2003 · I ended up backfiring through the carb a number of times the first time we started the motor due to having the ignition wires on wrong, and a couple of times since playing around with the timing. took the electric choke off an Avenger Backfire73-87chevytrucks. In any case, with the engine running, I would spray some extra fuel into the intake to see if the backfiring increases or decreases. Which you are describing might give more insight to the problem. The tailpipe afterfires happen more if I give it part throttle and go away if I give it more throttle. Seen a lot of posts about interference. It idles smoothly and revs fine in park. When I stomp on the pedal (idling) the car will sputter and if I press moderately it will spit fire out the primary and air out the secondary. co wfaxnpci tjszhn qfz ca0g pb3rf9 lx ord3xq d6zxmj mk2uucwc