Looking For Great Deals On Holley Carb Parts? From Everything To The Very Thing Dozens of Mustang Carburetors from #1 Rated Mustang Authority, CJ Pony Parts®. Save On Ford Mustang Carburetors, Gaskets, Mounting Kits & Studs. Shop Now Holley Carburetor: Idle and Transition Circuit Calibration Guide. it is a sign that the mixture is going lean. If this is the case, the idle jet needs to be larger or the air corrector smaller. A good test is to stick a wooden toothpick into one of the idle air corrector jets to see if it helps with the 3,000-rpm test. be sure to look.
Hey guys. I'm having a problem where when I first get into the throttle from a dead stop, like pulling away from a stop light, the A/F ratio goes dead lean, and the car stumbles for a second or two then clears up. Happens around 6-8% throttle on the datalogs. I have a datalog of a 25 min drive on the street, but don't know how to post it or how to post my Global Folder If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle Most of the 670 S/A's i've seen are set up extremely lean. Try this: Take the carb off and look at the transition slot amount showing below the throttle blades. It should look like a small perfect square, usually in the vicinity of .020-.030. Chances are that there is more showing due to you turning up the curb idle screw
My narrow band A/F meter shows off-the-chart lean. You diagnosed your own problem. 1st, there is no cruise circuit in any Holley type performance carb. There are 2 circuits. Idle and High Speed. At no throttle to light throttle, you are idling and driving on the idle circuit alone The passage goes back down to the idle screw. Somewhere near the top of the passage is a small jet. This is the idle feed restriction (IFR), or idle jet. The idle jet's up-and-down feed path prevents fuel from siphoning off into the engine from the fuel bowl through the idle circuit. The idle jet can be anywhere in this passage
780 Holley on my 355, having a bad lean condition going from idle to cruise and light throttle. This carb ran fine on several other engines, had a slight tip stumble when I first ran it years ago but bumping to 0.035 shooters cured that. Now it has this problem, may have been there all along and is worse now for some reason I had a similar problem with my 383 with Holley carb. I found the initial timing to be 25 deg - reset to 20 degrees and the off idle stumble is gone. I have 15 deg of mech advance for a total of 35 deg - all in by 2800 rpm
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 10.5:1 ratio at part-throttle. Holley carb, flat spot off-idle... Jump to Latest Follow If your transfer slots are uncovered you could get a lean spot as give it throttle because you have already pulled fuel from that circuit. Jim Langley Technical Editor Fordmuscle.com \'65 Mustang GT, 347 (Warp 65 I have a holley 750 vacum Secondary carb that Backfires through carb with a blip of the throttle. Seems like a lean condition? It Won't backfire if you slowly raise RPMS. It also has Off idle/transition bog/stumble- It cleans up when the rpms get to up ~1500 If you want to richen up the idle simply replace your idle air bleed with a smaller one (less air in the system = more fuel = richer idle), this will help you get your mixtures screws within the 1-2 turn range. What if you want to lean out the intermediate so you can get your car to come off of the transbrake a little cleaner I have gone through three 600 Holley carbs I bought from Summit Racing on my 16 year old daughter's stock 302 1970 Mustang Convertible. The car bogs right off of idle driving it normally. All three carbs did the same thing
Regardless if you have a two- or four-corner idle adjustment on your QFT™ carb, start by setting all of the idle adjustment screws the same (1-1/4 turns from bottomed out in the metering block is a good place to start). The engine should be turned off while you are setting the adjustment on all of the screws The most common cause of an annoying off-idle hesitation on Holley carbs is when the primary bowl has been removed and re-installed. It is very easy to replace the fuel bowl in a slightly different position that can create additional clearance between the accelerator pump cam linkage and the pump The IAB will lean the idle mixture but it will also lean the transition circuit by cutting it off sooner and possibly creating a lean hole prior to the main jet coming in. Most likely the IAB is a .073 or .070 much larger than .073 will most likely require a larger IFR and open up more tuning to make work . The mix ratio is determined by the idle air bleeds in the venturis and the idle feed fuel restriction in the bottom of the metering block. Air from the air bleeds is limited by the size of the hole Idle - At idle speed, the carb runs solely on the curb idle discharge port. Air/fuel ratio is adjusted by turning the idle mixture screws. Target an air/fuel ratio of stoich (14.7:1 - lambda 1.00) for standard gasoline. Engines with longer duration camshafts may not be able to maintain good combustion this lean
Next problem has was getting it to idle smooth but always quit on me so it seemed very lean. From reading on setting idle mixture screws and idle circuit tuning I got the symptoms mine was way lean and these holley 600 and street avenger carbs are known to have a very lean idle circuit Hi, I changed from a 4742 600 cfm vacsec Holley to a 4777/7 650 DP. Engine is a 390 GT (1967 S-Code Mustang) with Performer RPM, FPA Headers and stock Holley 650 DP part throttle too lean - 332-428 Ford FE Engine Foru TROUBLESHOOTING THE HOLLEY CARBURETOR With the engine off look into the carburetor bores. Fuel will be dripping off nozzles and/or the carburetor will be very wet. Adjust idle mixture screws to lean best idle. Repeat the operation on 2 and 4V carburetors. Now, turn mixture screws in until idle speed drops 25 RPM on tachometer another common fix i found is the idle air slot on the underside of the butterflies. from what i can tell, this problem really only applies to applications where the idle screws are way off from the standard 1.5 turns out, or where the idle settings have been stretched to their limits due to a radical cam or something of that nature. my cam is.
Using idle vacuum to set the PV choice is an exercise in frustration, the PV circuit is attached to the mains only, and they are inactive at idle and off idle/transition. It was Holley's way to get someone in the ballpark if starting from scratch Conversely, if off-idle acceleration does not feel crisp or clean, then the pump nozzle size may already be too large. In this case a smaller size is required. Holley accelerator pump nozzles are stamped with a number (Figure 5) which indicates the drilled pump hole size If your carb transfer slot is not at least showing .020 on your main idle speed then on take off it will be really lean and cause a slight lean tip in but not always. If your engine is pretty much a bone stock engine with nothing more then a rv type cam then it should not be to hard to adjust and tune it . The same is true with the high. A common one is when coming off idle it backfires, this is almost always due to having the idle screw turned too high on the primaries, exposing the vacuum advance port and letting the vac advance come in before the fuel from the accelerator pump shot makes it to the cylinder (lean, and overadvanced backfire)
Holley HP EFI goes Dead Lean off Idle!! Jump to Latest Follow 1 - 17 of 17 Posts. Radrick50 · Registered. Joined Aug 9, 2000 · 1,832 Posts . Discussion Starter • #1 • Mar 11, 2016. Quick Summary: I purchased a used Holley HP EFI system with Ford harnesses off a member on here.. Both of these carbs do this. Now, I have a Street Avenger Holley 570 cfm that is perfect and doesn't give me any problems at all. The trouble is I've got 3 390 engines and only one Street Avenger Carb. I've looked up the specs on each carb and it looks like the only big difference is the main jet size and the primary power valve size I also found today when I started it after sitting outside in about -10F all day, it started and idled nice but the choke started dropping off with how lean I have it in an effort to get it off high idle when hot. It then kept dying on me and I had to keep it above 1500 for 5 minutes or so otherwise it would die
How to establish a baseline idle mixture setting for your Holley carburetor and how to fine tune idle mixture and idle speed for your application Im a newbie when it comes to carbs so are there any adjustments i can make to lean out the carb some? Its blowing out some black smoke so i know its running rich so i just need to lean it out some. Its a Holley dual feed not sure on the cfm probably a 750.Please help.T.I.A In this video, we conclude the Holley Idle Circuit and mods. In this video, we conclude the Holley Idle Circuit and mods put 70 idle bleeds in and re-adjusted carb. If I get the idle at 13.xx on the wideband, there is still a very slight lean sport at very very light steady throttle, off idle. Usually lugging through a parkinglot in 2nd gear or just cresting a slight hill in 4th letting out. If I put the air/fuel in the low 12's at idle, it seems to almost disappear The Discount Inboard Marine team is going to show you how to adjust your Holley carb today!With just a few simple steps and you'll be on your way to a smooth..
One of the most difficult jobs on a carburetor is getting the proper idle mix. If done right you'll have a perfectly smooth idle. However, if done wrong, you'll wind up with stalling, pinging, and a rough idle. This quick walk-through will get your Holley carb up and running with a perfect idle in no time Realize for 99% of the motors out there the idle air bleeds that holley installed will do the job. And like I said earlier the idle circuit has no bearing on your AFR's at cruise. So to answer the OP's question, no, leaning out the idle circuit will not lean out your cruise AFR's are 2800rpm Although idle circuit adjustment is a prime criterion, the first step toward achieving a good idle and subsequent low-speed cruise performance is to first select a suitable carb. For a short-cammed street machine, the idle circuit of a Holley-style carb need only be on the primary side of a 4-barrel carb Floats are moving freely and are set correctly. When I turned in the idle mixture screws all the way, the engine did not stall. I measured vacuum at 18 at idle, so I purchased an 8.5 PV and replaced the 4.5 PV. After playing with it further, got the idle very smooth, but still couldn't get it lean. Opening up idle mixture hurts the idle 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 10.5:1 ratio at part-throttle cruise. The WOT air/fuel ratio was only slightly rich at 12.2:1
Check for lean condition (need larger jets or larger carb). Check for vacuum leak. Check for excessively retarded ignition timing. Check engine temperature. Check camshaft timing. Blower makes noise when new. The Teflon that Holley uses to seal and properly clearance the blower will generally make noise while it is breaking in A Holley carburetor is made with four basic parts, the throttle plate, main body, metering block and float bowl assemblies. 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
If the engine seems to have an off-idle stumble, changing the size of the squirter itself can fix this issue. The first thing to do is determine whether it's a lean or a rich stumble. If the engine seems to take a deep breath and then accelerate quickly (almost like the iginition cuts off for a split second), it's generally a lean stumble Hi Patrick my carb number is 30792 i need to richen up the idle circuit its a touch lean at idle. lambda readings at idle are 1.05 to .98 would like it down around .90 the idle mixture screws are out to 3.5 turns. i also tried dropping the idle air bleeds from .060 down to .042 and no change so dropped it to .028 and still very little change. idle fuel pressure is set to 7.5psi with your. This will assure that there will be no lean stumble when the carburetor comes off idle. Tuning an accelerator pump for maximum performance off the corner often involves reducing, rather than increasing, the pump volume and discharge rate. Drag racing calls for a slightly different approach
Lots of folks lately with Holley issues. I am trying to tune out a hesitation in the off idle part throttle range. The carb I am using is a NOS Holley 9834-1 Here is what happens: Car starts fine hot or cold. Electric choke works great, after the choke comes off and the car idles at 800 rpm glass smooth. I can get 20 hg at idle, steady gauge with no fluctuation With the PTSR 0.083 and STSR 0.079 the engine did idle great, but as soon as the throttle blades move the engine quits, dead rich and flame out. So PTSR 0.075 and later 0.079, with the mixture screws pri 1 1/4 open and sec 3/4 open. Rich idle AFR 12, when driving its to lean with a coughing engine This carburetor has front and rear metering blocks with four corner idle screws and the only way it will idle reasonably is if I lean the two rear idle screws all the way in (so they are effectively disabled) and the front two screws set at ¾ of a turn (which is a bit shy of where it is claimed they should be at 1 to 1.5 turns open)
The idle mix will make a slight difference, so set that with a vacuum gauge and tach to get the best mixture. I actually have my idle mixture a bit rich now to help cover skipping in the throttle right off idle. It's just a matter of fiddling with the mixture to eliminate the lean misfires The only way we got off of the lean spike with either the smaller holley 1850 style or the 750 quick fuel 4410 style was to put heavy springs on the counter weights. Bottom line, we should have just locked the distributor out at 36, but I cant get past that not being a chevy thing to do as you're saying idle will be rich and mid-full power will be lean due to poor signal. you'll have to lean the idle circuit at the idle restrictions and richen the jets until it AFR's right and even then you'll still have transition problems pretty sure a good old 650 double pumper will roc Hi all, I've got a Holley 750 vacuum secondary carb with a Proform main body, It's idling rich and adjusting the mixture screws to where the engine seems to like it (about 1 1/2 turns out) doesn't change the rich fumey smell. Is there anything else that can be adjusted for idle mixture entering the carburetor. Holley performance carburetors are equipped with a fuel bowl of this fuel is then bled off to an idle well where it is mixed with air from the idle air bleed hole. The idle well leads directly to the Turning the screws clockwise will lean the idle system. Conversely, turning the screws counterclockwise.
you achieve the highest possible vacuum reading without adjusting the curb idle speed screw. Turn screws in to lean the mixture. Turn them out to richen the mixture. 4. Now that the idle mixture is set, it may be necessary to go back and reset the idle speed using the curb idle speed screw. 5 Reverse-idle with a Holley carburetor means simply that turning an idle mixture screw clockwise richens the idle (and transition) air:fuel mixture, and vice versa, turning it counter-clockwise leans the idle (and transition) air:fuel mixture. This is the opposite of the original, traditional function of the idle circuit mixture screws i Re: holley idle mixture screws Some hollies are screw out to richen others screw in to richen depends on when they where made General rule of thumb adjust to best smooth idle then lean out 1/4 of a turn. If you are not in the holley specs with mixture and/or idle stop screws adjust the secondary stop so they are Most performance-oriented Holley carbs have jets on both the primary and secondary sides. The jets are accessed by removing the fuel bowls on each end of the carburetor. But there is an important exception: 4160 carburetors (such as most O-3310's and O-1850's) do not have replaceable jets on the secondary side
But my idle is really lean. If I turn the jets in 1/2 turn, the car will barely idle and stalls if you give it any gas. I am getting an ok pump shot, but nothing as strong as I'm used to seeing on a Holley 4 barrel. Even with the rich jets, it hesitates off idle unless you ease in the throttle. The idle mixture screws are at 2 turns The best way to set the idle mixture is to lean the carb out until the vacuum just starts to drop, and then richen the mixture by about 1/4 turn. If you have a bit of a stumble in very light, low speed operation, sometimes it helps to richen it up by another 1/4 turn 3. Place the carburetor on top of the flange gasket on the manifold. Install the hold down nuts and snug down progressively in a crisscross pattern (60-80 in./lbs.), as shown in Figure 1. Figure 1—Carburetor torque sequence (all Holley carburetors) WARNING: Overtightening may result in a warped or cracked carburetor throttle body. 4 Holley carbs come with a standard shooter size which differs by carb list #. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. 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 Carburetor Tuning Step-By-Step. Okay, now comes the fun part. A few preliminary adjustments can be made before installing the carburetor on the engine. One is to preadjust the idle mixture screws to about one full turn out. Do not overtighten the idle mixture screws as doing so can damage the needle tips
Hi, I've got the 250 six cylinder with Holley 4BBL 390 CFM, bumped up compression, larger intake valves, and a moderate CAM. Hesitation in acceleration, occasional backfire through the carb. Looking at the Holley video, it looks like I have too small accelerator squirter. mine is 25.. Sometimes, removing the idle mixture screw, blowing compressed air into the hole, replacing the mixture screw and readjusting the mixture may cure this problem. Often, a poor idle condition will not be the carburetor's fault, but a clogged Positive Crankcase Ventilation (PCV) system. With crankcase blow-by gasses unable to escape, idle will. Holley carbs have several operating systems, all of which can be tuned independently. Often, an improper setup of one system will give false indications of a problem in another system. Attempting to cure Holley problems by tuning the wrong system results in a really messed up carb, and a lot of frustration for tuners and car owners Surging is usually an indicator of a lean-running condition. Check for vacuum leaks at the carb base, the intake manifold where it installs to the block (or the heads if not a flathead) and any vacuum-driven accessories and their hoses or pipes (even a leaking 1/4″ wiper motor or trans modulator hose/pipe can affect idle characteristics)
I readjusted the transfer slot to holley specs. Increased the idle air bleed by 4 sizes higher. my car went from 12.2 A/f to 13.8 A/f at idle,. went one size higher on the air bleed and obtained 14.4 A/F ratio. my idle screws now have adustment and idle is crisp and no dead spots off idle. Idle Air bleeds are the outermost bleeds Carburetor idle circuit fuel is metered to the engine below the throttle plates. If you see any white smoke billowing out of the carburetor with the engine off there is an internal fuel leak. I installed 3 new holley carbs on my 427, it has alu. heads and 11 to 1 compress. The intake is 3919852 37-119: 37-933 6-506: 122-62 N/S: 125-85 0.025: Plain 108-83-2: 108-89-2 108-90-2: 108-27-2 N/A: 134-105 1-3/16: 1-1/4 1-1/
Rough, erratic idle that drifts toward higher RPMs than expected based on the setting of the curb idle screw. Sometimes a lean condition will cause a hanging idle that is slow to settle down to set idle speed. Backfiring ; Sluggish hesitates when the throttle is opened, then recovers (often accompanied by a slight backfire having some minor issues trying to get a slight off-idle bog possible lean tip in ,i've got the a/f screws right now about 3/4 out but it did idle better at 1 turn out originally but slight rich sensation eyes watering but not very bad but noticeable . Probably went the wrong way in adjusting the carb but tried to solve the lean tip in first. Most Holley carbs are fitted with no power valve in the secondary metering block. However, some carburetors may be fitted with a secondary power valve which can be used if additional fuel is demanded on the secondary side. If not, the power valve opening can be blocked with this simple block-off plug from Holley (P/N: 26-36) The engine is running lean off idle, and eng temps (the new thermostat described above), and decreasing the idle air bleeds from a base of 65 to 61 has greatly improved the performance. Other changes include a 50cc pump and a nozzle jump from 35 to 40 and a 6.5 PV. The carb is a 4150 pattern 4 corner idle double pumper. 234 centerline.
Fine-tuning the carb in this manner will improve part-throttle operation and should eliminate that annoying off-idle stumble. As you can see, there's much more to setting idle mixture properly. Get yourself a wideband,vacuum gauge and tach and go for a drive,pay attention to all, then close the idle mixture screws (which shut off a very rich air/fuel blend) turning them in on a normal Holley based carb. struggle to keep it running and watch how lean the mixture goes all the way up The Holley 1940 was used as a replacement carburetor for the Autolite 1100 carburetor. The 1940 was also used on a lot of industrial application. Wood chippers seem to come up a lot. There is nothing wrong with using the 1940. In fact in some respects it is a simpler working carburetor than the Autolite 1100 is
So my car runs great. Its a crate motor zz385 (10k miles) with a holley carb but not sure which one. I know its a double pump, maybe 650 or 750. But I've noticed that when I stomp on the pedal it really hesitates then takes off fine. I had the idle too low at one point (about 450) and slightly increased it to about 600 Some carburetors have a reverse idle adjustment (some 2300, 4150 and 4160 Holley carbs, for example). On these carbs, the air/fuel mixture is made leaner by turning counterclockwise (or OUT) and made richer by turning clockwise (or IN). When in doubt, look up and consult the factory manual for your specific carburetor I have just bought a Holley 4160 600 cfm carb, put it on my Edelbrock eps manifold, and the off idle stumbles pretty bad. It gets up ok on the freeway, and when I get on it a bit, but even still is a bit rough. it acts like it is choking out a bit, and when I get on it hard, it accelerates smooth enough, without the pause, but kinda peeters out when the down shift is almost coming off, kind. If the throttle is eased into the off-idle position and the motor stumbles, the idle circuits and the transfer slots are probably too lean. To cure this condition, either slightly undo all four idle-mixture adjusting screws to enrich the system or enlarge the idle-feed restrictors in the metering blocks Don't set it too high, as this will cause causes excessive clutch and brake wear. The Idle only needs to be 7 to 900 RPM with light load or AC on. 5. Recheck timing and vacuum hook ups. Recheck mixture screw to lean best idle again. If all is still best and smoothest idle then confirm and note the final settings