454 backfiring through carb Jan 15, 2011 · Hi, you have been given a lot of ideas on possibilities, But one common one that hasn't been mentioned yet is that the accelerator pump in your carburetor might have quit working. Customer: 74 454 won’t stop backfiring through the carb. Backfire thru carb. 454. Lean mixture when accelrating. Check for moisture both inside and out. Sep 29, 2012 · i have a 77 c20 with the 454. However it's running horribly all of the suddena few months ago it ran great, and now all of the sudden it runs like crap. 4L Mercruiser. to/337zElZWe Aug 17, 2015 · Random old car troubleshoot Re: Idling and backfire through carb-look for disconnected hoses, wires and tubes, etc. If you would like to help support the channel you can do so by Dec 27, 2011 · Recently, my 454 has developed a backfire under a heavy load. That should get it running. Missing, popping thru exhaust bad on pass side, ocasionally backfires thru carb, have checked spark, timing, pulled valve cover to see if I had broken valve spring. It is also commonly caused by the accelerator pump inthe carb not squirting enough fuel before the main jets start working. 10 min read Share Troubleshooting - backfire through carburetor. So I put some NGK plugs in and it ran perfect. Oct 4, 2018 · I have a 350 4 bolt that sat up for a few years and I have been trying to get it back on the road past few months. On a 300 mile round trip last weekend, it started to miss and backfire through the exhaust. It probably is too rich to run. Last night I put my foot up it and it did a big backfire through carb and has run rough again ever since (backfiring through carb if I go over approx 2000rpm) Mar 3, 2010 · Hi there pirates!!! It is my sincere hope that someone here will be able to help me out. Thought I had it, but alas seems to change its mind if I look at it funny. Sticking valves can also cause this. It sounds like the carb float is stuck open and the pump is pushing gas out the carb, flooding it, and spraying gas around. May 4, 2012 · I've got a '77 Argosy moho with a carb. Troubleshooting - backfire through carburetor. i will hook up better leads with better connections and if that fails it will all go on ebay!!!! Dec 19, 2018 · Backfiring through the carb (spitting or coughing) usually occurs in the morning when a carb's air/fuel mixture is a bit too lean. 55 12-bolt posi If it backfires through the intake it is a timing issue, either ignition timing or valve timing Jul 4, 1990 · Customer: Have a 1990 7. New cap, rotor, plugs, ignition module, plug wires, and carb overhauled. Found the CTS to be bad. This was causing the rough idle. Once warm, it runs much better, but still does not respond smoothly after 1-2 upshift and when pressing pedal from cruise at 40-50mph (slight hesitation). Electricity, especially high voltage, will find the shortest path to ground. This is a very common problem with cars today and the fix can be very e Mar 20, 2004 · I'm stumped! I've got an '83 3/4t Silverado. Try running even more timing (if you can't verify TDC) and see if it runs better. If it still backfires, check the timing, and set it to stock or 8-10 deg base timing. Backfiring isn't just loud and jarring -- it's also a bit embarrassing. You might be too retarded if the balancer outer ring slipped, causing you to think you are too far advanced. to/2U3tDCOMy MSD Pro-Billet Distributor: https://amzn. . Vacuum gauge I use in the video: https://amzn. Backfiring through the carb mean that a intake valve or valves are open when the plug is firing. Not sure what fuel you run (ethanol or non) or if your carb has the correct ethanol-friendly float-valve and accelerator pump plunger. The engine needs fuel to burn along with the air the engine is processing. Double check your timing, the vacuum advance (disconnect the VA hose from the carb and suck on it to make sure the diaphragm is still good) and your mechanical advance (make sure the weights move freely), etc. Jan 11, 2012 · I have an issue with my 1968 Chevelle. Jun 5, 2010 · Re: 89 Ebbtide 7. A new gasket fixed the the idle problem. Put back the AC's and everything was fine. Cruising toward home Apr 18, 2025 · A Chevy big block brings the thunder, whether you're roasting tires with a rowdy 454 or towing your toys in an 8. it stumbles under acceleration from a stop. Turned out to be faulty Champion spark plugs. Unless the cam timing is way off it is usually caused by ingntion timing. Backfiring through carb. The left exhaust pipe is significantly louder than the right one, and Oct 2, 2012 · The car ran fine until the #7 intake valve hung open earlier this summer. Usually backfiring through the carb is a lean mixture or the spark plug wires are cross-firing. Bill Tichenor. Ignition timing issues are another culprit. Apr 10, 2006 · Backfiring through the carb is almost always a timing issue. Bad cam? Not a pro but know that if running rough and backfiring thru carb a lot of times is 03-11-13 08:49 PM - Post# 2325262 In response to hobbschevy4life A few things to try. If the mixture is too rich or too lean, it can combust at the wrong time, leading to a backfire. I have a rebuild 454 in it and just recently started backfiring/popping out of the exhaust at idle. It also has Off idle/transition bog/stumble- It cleans up when the rpms get to up ~1500. can be timing too far advanced. I replaced the cam with a summit K1106 cam and new GMPP aluminum fast burn heads. a leakdown test will be more accurate than a compression test for this action. Now it even does it idling when the timing is set correctly. 69 SS/RS Fathom Green 454 4 speed Bumper sticker- My other auto is a . Improper Fuel-Air Mixture. My first move would be a carb rebuild. Once choke opens, sputters / backfires through carb and hesitates/dies when starting from a stop and after 1-2 upshift. in this video I describe how I repaired the popping coming out my exhaust on my 1970 chevelle. The car idles well and will run fine at higher rpm if I come up in rpm gradually. When it comes to engine backfire through the intake, there are several key culprits that can ignite this explosive phenomenon. Oct 30, 2009 · The carburetor gasket was blown. I keep adjusting the distributor and then sometimes it seems like it’ll work fine idling and revving up when in park but as soon as you start driving and revving up on the road it’ll backfire again. Also most engines need the throttle pumped a bit to get them to start cold. When I got the rig, it ran pretty good but with high idle. It will sound like rapid sharp backfires from the carb and is caused by a problem in the distributor such as bad pickup,coil,rotor, cap or worn distributor shaft. Internal combustion engines run on a mixture of 14 to 1 which is fourteen parts air to one part fuel and when this is not correct (not enough fuel) the result will be Sep 25, 2004 · '71 SS 454 - Canadian Built 468" BBC, M-21, 3. May 24, 2025 · Why Does My Car Backfire Through The Carb? Your car may backfire through the carburetor due to a few key reasons. When my dad and I pumped fuel into a cup there was a layer of water on top of the fuel. It had been sitting for several years, but I have been working on it, and I have gotten it up and running. The vehicle is a 70 El Camino SS 396 with a Apr 20, 2017 · On cold starts I hear random backfiring out the exhaust and rough idle. Before yesterday, the car ran great, better than it has ever run before. Apr 25, 2024 · The #1 reason for an engine backfire through the intake manifold will happen under load or acceleration. The fuel had water in it. One common cause is an incorrect air-fuel mixture. Oct 20, 2022 · What Causes Backfire Through Carb The carburetor or carb regulates fuel and air flow to your car's engine. The tare down to see the lifters and cam to make sure what is wr Aug 30, 2004 · An intake will make fire come out the carb, An exhaust will make a backfire out the exhaust. Let’s explore each one in detail: 1. Jul 27, 2013 · Hey ive been chasing a misfire on my 59 chevy for about 6 months now and finally found the source. Now getting a backfire through the carb (seems to always be the one over the 5/7 cylinders) on acceleration. I just recently put a demon carb on it and it ran fine with no backfire. to/39LnL7QFord HEI Distributor: https://amzn. This happens regardless if the EFE flap in the manifold is open or closed. Check at the rear / baseplate of the carb for pipe plug missing. This usually goes away once the engine warms-up. 1 turn out on all 4 seems to give the best response. An improper fuel-air mixture is one of the primary reasons behind engine backfire through Oct 15, 2001 · You will get more expert advice than I can give but here is my understanding of things. Did you check the in-line fuel filter at the carb inlet? Years ago I had the same problem in a Corvette I had. Fouls the #8 plug. Nov 24, 2013 · I hope your carb guy checked for a ruptured power valve, a fairly common problem when it backfires through the carb. I keep adjusting the distributor and then sometimes it seems like it’ll work fine idling and revving up when in park but as soon as you start driving and revving up on the road it’ll backfire again Aug 2, 2009 · heres a video of the problem can anyone tell me why its doing that? its got a 454 bb, holley 750 carb. How old are the spark plug wires. Mar 23, 2005 · My 70 El Camino started backfiring quite badly through the carb with a ball of flame coming out. helped my problems out quite a bit. Late carbs do have a check valve in the port that will "help" protect the PV, but it should be checked anytime the engine backfires. It does go away eventually the more I drive it. Has a 750 Holley, and it's basically an all stock engine. With the engine off, and the air filter lid removed, move the linkage and you should see two tiny, steady streams of gas, squirting into the primary venturi's. I've never messed with the thing. Jul 12, 2014 · She accelerates really smooth but on hard deceleration I get backfiring through the carb. Double check TDC on your balancer. Once it warms up it seems to be better but will still backfire through carb if you floor it. The old distributor cap was black, the new Borg Warner select was grey. Feb 5, 2018 · If the backfire is random, or during acceleration, could be too lean. now its just the initial start off from a stop. Try a partial choke, see if that improves it. Jan 8, 2011 · 454 chevy with HEI giving me fits. To diagnose a worn valve seal, first, check for engine knock. accelerator pump to short) Vacuum leak causing lean mixtur Nov 23, 2022 · Lastly, when a valve seal is worn, it can cause a backfire when accelerating with the carburetor. has new distributor cap new oxygen sensors runs good at low speed backfires through carb at load Apr 28, 2005 · Runs at high speed and won't idle, is a sympton of a LARGE vacuum leak. Thought someone might know what I can try to solve the problem. The engine was just rebuilt, and the carb was also restored and rebuilt. To increase the timing, rotate the distributor counterclockwise. 1L Vortec-powered rig. Specifically, when I jump on the engine just as the car is shifting to second the engine is backfiring. Starting when cold or after a few weeks of non-use is usually as follows: push the accel. Vacuum will be low and pulsing. The backfire at the carburetor caused the carburetor gasket at the intake manifold to blow out. its easy to eliminate it as a cause. Inside the coil area where the coil sits in a pocket in the HEI distributor was black with carbon, I had a ah-ha moment--- the coil was bad and arcing through the plastic to some of the plug terminals causing the backfire through the carb. The car prior to the carb being rebuilt was running rich and after the rebuild seemed better but then starting running rich again. Once I put it Aug 14, 2008 · will the car run or just backfire through the carb? if it's been out, it may be 180 out, that will back fire be sure the number one wire has the rotor pointed to it on top dead center of number one cylinder if it backfires through the carb one of your intake valves is open during igniton on one of the cylinders Backfiring Through Carb If your big block is spitting fire through the carb, something's off, and it's not just your timing. timing is quick and easy to check and can cause that problem. i just did plugs and wires, looking to replace cap and rotor since i just replaced the vacuum advance on it. When I stomp on it or give it quick throttle at the carb it backfires through the carb. I rebuilt the carb, changed the plugs, wires, intake manifold gasket, wired up an MSD dist Re: Backfiring through the carb 10-13-02 01:18 PM - Post# 129654 In response to I don't think what your hearing is a carb backfire problem but spark scatter. Apr 29, 2019 · OK, so having a bear trying to get the SBC running smooth. Also check the PCV valve port on front of Carb. 12/02/2009. something is wrong, just dont know where to start. I've changed the Centrifugal advance weights to heavy springs, advanced the vacuum advance and retarded the timing. This causes a lean mixture in the carburetor, which can lead to pre-ignition and engine knock. I replaced the plugs on the road and this cured it. Forums to Be Paused as We Explore New Community Tools After careful consideration, Family RV Association will be pausing the Forums effective May 9th, 2025. Jun 18, 2007 · The 454 Magnum came with a Quadra-jet carburetor. Barry Blackburn/Shutterstock. Its got 1980ish 454 motor. My 81 with a 454 and smog has started to backfire horribly when I give it any gas at all. (carb. Once it reaches operating temp, backfiring improves but it doesn't go away. Feb 10, 2019 · 305 tbi camaro backfiring through intake? What could be the problem. Both of these are at "manifold" vacuum. Jan 21, 2017 · So after a few months i finally fixed mij backfiring issue thru the rear carb. The backfire is caused by the leaking of air through the worn seal. The carb has been running rich it seemed lately as there is a lot of carbon coming out of the tail pipe. backfires when accelerating hard. It's backfiring through the carb. 5- above only applies if valves are set, cam is installed correctly, distributor is on #1 on the compression cycle, Take your time. -check the timing-pull, read, clean, replace, whatever all the spark plugs-Mityvac all the diaphragms-clean and gap the points (obviously, re-check timing)-open the fuel line somehow near the carb and blow bubbles back into the tank May 5, 2009 · I'm working on my 66 Chevelle, with a 454 in it. It is a project car so i don't drive it much. it only dose it under load, i can rev it up on park, and it revs up just fine, but when im driving, it feels really sluggish. Although many modern vehicles have dumped carburetors in favor of car's computer-controlled fuel injectors, older vehicles still include this component, which requires maintenance and cleaning to prevent car backfiring. -----JT 71 SS 350 soon to be 454 Sep 21, 2006 · I have a holley 750 vacum Secondary carb that Backfires through carb with a blip of the throttle. 700R4 TV cable is adjusted properly - upshifts, downshifts, TC lockup Oct 12, 2014 · It was backfiring through the carb and 3 plugs were black (AC Delco R44 XLS). Nov 12, 2012 · C3 Tech/Performance - Backfiring through carb - I have a 1977 vette that I inherited from my uncle. I started noticing a backfiring and stumbling when you accelerate from idle. If so check the fuel supply to the carb, pull the drain plug, should get a steady stream. A pop through the carb can be caused by timing to far advanced causing the spark to happen while the intake valve is still opened while a pop through the exhaust is the opposite, the cars timing is retarded causing the spark to happen while the exhaust valve is still opened. 45. It has a heavy misfire and lack of power on acceleration, ran fine at idle. Tried everything, cleaned both carbs by ultranosic bath but still the same Today i let the bike run in idle on the front cillinder and disconnected the rear coil, after 30 seconds i switched over to the rear Nov 26, 2003 · Re: 454 crusader backfires thru carb at wot hello<br /> yep what bubbakat says. I have a beast running a 1990 454 with TBI. It has PLENTY of power and torque in my 81 camino, but when i'm coming down from a high revolutions it wants to backfire through the exhaust it does it when i'm coming down an Sep 9, 2010 · Remember also, if you have a Holley carburetor the power valve is likely to be damaged by the backfire. Start with the distributor cap. Misses and backfires thru the carb at 3200-3800 RPM. How to fix a backfiring engine by showing you the most common symptoms and solutions. Mar 29, 2006 · Ok, here is the story. Today I did a test drive and the thing just started popping randomly at 25mph. SBC 283 with 4 Holley 94. Oct 10, 2004 · Ok, i have completely new valve train, ignition, and carboration/intake systems on my 1974 454 chevy big block. So I get to my destination and pick up my truck camper (reason for trip). It sounds like the carb is loading up due to poor fuel Diagnosing the 454 BBC from the 52 rat rod for a backfire through the carburetor under load. Footage taken from Holley Carburetor Installation & Tuning DVD Apr 14, 2009 · If it starts and runs, you most likely have a carb prob. Jun 10, 2007 · If your timing is set at 0º TDC, or after TDC, it will backfire through the carb. You may still have a vacuum leak, check torque on intake bolts and make sure your carb gasket is sealing properly to the intake. Jul 28, 2010 · 1999 suburban with 454. May 1, 1999 · The distributor doesn't have to be off 180 to backfire through the carb, I had mine retarded 30 at idle and it backfired through the carb. if it's warm, its a lot less noticeable. it is carburated. Jun 3, 2013 · 4- hard starting, backfire thru carb is to much advance or valve not shutting on intake. Jan 22, 2014 · You can check the chain by putting a timing light on it and seeing if the timing doesn't move around while idling. Compression would be low or 0 in some cylinders also. Have a timing light connected and set the timing correctly right after it starts. Replaced it, and began to get a backfire through the TBI ONLY under load and Mar 7, 2011 · the tech said if i had backfiring through the carb then it would be a interference issue, but its back fring out the exhaust so he thinks its the power leads and maybe ground. It cranks right up and idles fine, but once I press down on the gas it backfires through the carb. For the last year, it has started and run just fine. It has been giving me so much trouble backfiring through the carb. If they are not properly routed with separation, they can cross fire. pedal to the floor 2-3 times, then fully release, turn-key, crank for 5-10 seconds, engine starts and runs at a high idle, throttle blips over the next 5 min Feb 7, 2024 · Unraveling the Causes of Engine Backfire through the Intake. Establish TDC, and install distributor on #1, and wire correctly. 4 merc to backfire out of the carb? I tried one other carburetor and it was still backfiring. I can't pin down the cause. especially when cold. Once you get it to idle, then you can set the timing. Set valves correctly. Dec 13, 2010 · Most likely cross fire under load. All recently rebuilt. Seems like a lean condition? It Won't backfire if you slowly raise RPMS. 4 454 backfire out carb Compression results 1 150 2 135 3 150 4 125 5 130 6 130 7 130 8 130 I am not much of a mechanic, but could anyone tell me if these compression results would indicate a major problem and cause my 7. opuyyb mscuow qbbek onwl cgh ovoshh cndqa jsfezbd pkgs iyoqaum