Holley mixture screws all the way in. A lean primary mixture will cause a major light throttle surge. Mar 29, 2018 · The 670 street avenger out of box specs are as follow. If the engine idles Jun 4, 2020 · 9:1 Compression. 028 and Power valve restriction . The adjustment procedure is exactly the same except that all four idle mixture screws are adjusted instead of just two. . Turn the mixture screws all the way in but not at all over tight. With the engine idling, pick one of the idle mixture needles and turn it in 1/4. It sounds like you may have a Holley carburetor with four idle mixture adjustment screws. - screw in all mixture screw until it lock. Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the sound of the idle. Back off 2 full turns form there. 22 inHg vac at idle. Mar 26, 2016 · If it won't run with your idle mixture screws at 2 turns out, throttle plates adjusted properly, and CHOKE OFF. Once the engine's idle speed has begun to slow, back each idle mixture screw out 90 degrees to complete the process. In, rich. May 10, 2004 · Phil, The air/fuel mixture screws adjust the fuel/air mixture at idle. Now you should be able to use you idle mixture screws properly. Continue to turn each screw in 90 degree increments while listening to the engine's idle speed. if you have a mild cam the is the best Holley 600 available, IMHO. Jan 11, 2012 · 1. Cork. Thus you can observe how the adjustment process changes the behavior of your engine. 5 turns out from bottomed. These carbs are designed to draw fuel from both the transfer slot and the idle port at slow idle. Sep 13, 2000 · Yes, Try screwing the small idle mixture screws all the way in til they lightly seat, then out 1 1/2 turns. You must do both screws equal number of turns. You can see in the pump cam picture that you are pretty much maxed out with the blue cam in the 2 hole position. Step 3. Jan 8, 2002 · The idle mixture screws don't affect the transfer slots. That's a likely possibility and good way to describe it. Start the engine. Then proceed to the second mixture screw and set it to the highest reading. Turn the ignition key and let the engine start functioning. to stabilize. Aug 21, 2017 · The first step is to set the curb idle speed to between 750 and 850 RPM, then check ignition timing and adjust if necessary. Last edited by PaceFever79; 03-11-2009 at 05:40 PM . Dec 9, 2003. Phila. Apr 13, 2006 · By turning in the mixture screw, you have effectively cut off nearly all available air and fuel. 2. Turn each screw in 1/4 of a turn and wait for a second for the vacuum meter to catch up. Make adjustments 1/2 a turn in either direction to find the smoothest idle speed. Float level is correct, not set to high. #1 · Feb 14, 2009. 9 AFR, literally eye boiling. Idle Mixture Screw Gaskets. This is an older thread, you may not receive a response, and could be Jun 4, 2020 · 9:1 Compression. screws, which will increase the pressure across the idle air bleeds, pushing more fuel from the idle well creating a richer fuel/air. Jul 27, 2015 · If the idle mixture screws make little difference to the idle from the full-in to the full-out position, it’s a fair bet that the butterflies are too far into the transition slot. Jul 29, 2005 · Set your float level and adjust your fuel pressure to stop fuel from dripping out of the boosters at idle. So there you have it, the idle circuit is mostly wide open for inspection, the only concealed section is where the fuel rises after it gets it supply and terminates at the restrictor. #1 · Aug 6, 2003. Set this screw until you reach the highest manifold reading on the gauge. I had an allen set screw in the secondary stop so I adjusted the secondaries open until the primary idle speed screw could be backed down all the way, but even then there was still no response from the idle Sep 11, 2023 · The idle mixture adjustment screws on a modular Holley four-barrel are found on the sides of the primary metering block. Now we are ready to set the mixture screws (Holley part # CS1540, Demon Part CS1540KH). If you want to start from scratch, make sure the screws are lightly seated when you turn them in. Aug 29, 2020 · Idle Mixture Screws, Holley Street Avenger. 050", 271°/280° advertised, 410"/427" lift Jul 24, 2009 · Idle mixture is a combination of the air going into the engine AND the emulsified fuel coming out of the carb. Idle the engine until it is heated. Dec 2, 2009 · 358 Posts. Repeat. Then I move to the secondary side, doing the same thing. Here's a quick trick to know which way to turn those fickle air fuel screws just by looking at any carb body! #shorts Subscribe for the upcoming complete ser May 10, 2008 · Because there is a relatively large amount of air bleed in the over-all circuit a relatively larger idle jet is necessary to get curb-idle screw sensitivity as desired. 12btdc initial, 34 total non vacuum advance distributor. Like. I opened the rear secondaries a little and some adjustability has come back. Hey, all, I was trying to do a bit carb sync today, and noticed that the engine still runs even when mixture screw is turned all the way in. Apr 23, 2015 · Even "two corner" idle carbs have a fully-functional (but non-adjustable) idle circuit for the secondaries. So I guess nothing is coming out of that side. Turn them slowly clockwise and counter-clockwise until the vacuum gauge reads the highest possible reading you can achieve. If manifold vacuum increases repeat the process, letting the idle. It runs i believe 24 degrees intial. , sounds like you will have to turn them in abit, then reset the idle speed. Cover carb with a rag 3. Rear Metering block conversion with rear block from a 4777-2 carb. yellow heap. Video. The way to set your idle screws properly is with a vacuum gauge. Location: San Francisco bay area. 480) with 1. 1 to 10. When we turn the idle mixture screws, they do nothing, we run the car with both of them turned in, and it doenst even shut off. Feb 17, 2021 · Many Holley performance carburetors are equipped with what is called four-hole or four-port idle mixture control. You'll find that the screw is nearly all the way in. You need to run the engine and warm it up before adjusting the air-fuel mixture screws. I would have thought it should go down and of course kill the engine. Finally I do both at the same time, adjusting all 4 mixture screws at once, but with smaller adjustments. For now, disconnect your vacuum advance and plug it off at the carb. For those with two screws, turn the mixture screw in until you notice a drop in Jan 2, 2007 · Now the fine tuning. Repeat this process for all of the idle mixture screws. #2. 480 lift. A helpful hint: All of the vacuum readings on the vacuum gauge should be the same for each screw you adjust. Turn each idle mixture screw, one at a time, in a clockwise direction 90 degrees. If still surging, check TOTAL advance, ( initial + centrifugal + vacuum) Too much advance will cause Mar 11, 2009 · Then start the car (it will probably be idling very high now) Then turn the secondary stop out until the idle starts to come down to the desired level. I can screw the idle mixture screws all the way in and the engine doesn't die. In the context of racing carburetors, it helps to think of them as (4) one barrels. The air/fuel mixture screws are key to setting the idle. Shut the engine off 3. It also starts to cut out around 3500 rpm's. This engine runs best at 36 degrees. View Details. Blueprint aluminum heads. An Article About. Remove both screws 2. Jun 4, 2012 · Turn them slowly clockwise and counter-clockwise until the vacuum gauge reads the highest possible reading you can achieve. Re: holley idle mixture screws. I couldn't get the idle mixture screws to adjust and I figured out the transfer slots were exposed. Sep 22, 2014 · Tuning 4 corner holley (quick fuel) mixture screws. Turn the screws all the way in until lightly seated 5. #2 · Dec 2, 2009. Cam is 207°/214° @ . Anyway, I was Nov 16, 2019 · If one wants to you can make it a 2 corner setup by taking out the rear idle mixture screws and putting in some brass allen screws and then take the rear idle air bleeds down to a smaller size to compensate with there no longer being the idle mixture screws being there so its not way lean that point and put in around a . Install a vacuum gauge to a full manifold vacuum port 4. 25 turns open on the mixture screws. 5ish in gear, it can idle like this all day long. Dec 3, 2018 · 1. 031 shooter and orange pump cam. 66 jets all around. Started engine and adjusted idle screw until idle was 1000 rpm. Jul 14, 2010 · The amount of air bleeds a carburetor will have is dependent on the number of throttle bores and circuits the carburetor has. I once had a tunnel ram setup on a SBC with two Holley 600cfm, 4-corner idle carbs. First let me say that the engine runs fine in spite of the almost complete unresponsiveness of the idle mixture screws. Oct 5, 2007 · holley 600cfm carb 4160 anyways, the idle mixture screws do not work on the car, it runs with the screws turned in. Dec 16, 2011 · Re: 850 Holley idle mixture screws- idle issues. Adjust each screw in equal Apr 23, 2020 · Both idle screws should be the exact same number of turns out at all times. Also, I put some clear sight plugs on the bowls. These carbs employ two more idle mixture screws on the secondary side of the carburetor. Mar 25, 2019 · increases during the adjustment process, adjust it back down to the desired rpm and continue mixture screw adjustment until the engine RPM or vacuum drops. May 14, 2018 · The idle mixture screws made no difference in the idle speed or vacuum reading, and even screwing them in all the way had no impact. 10/pkg. Want more in-depth information? Check this how-to-guide on Holley carburetor problems, possible causes, and corrective actions. NEVER screw the idle mixture screws in all the way and too tightly. May 18, 2008 · I do this by adjusting the primary side first, adjusting the mixture screws equally every time by 1/8 turn, and allowing a few moments for the carb to adjust to the settings. If they are not the same, set them at 1-1/2 turns out (counterclockwise) from fully closed. To get the idle mixture right the screws must be turned nearly all the way in, which according to the decal on the side of the metering block makes it rich, not lean as usual. now you can set the idle air fuel mixture. They should be square with the throttle blades closed. Comp 280h (230/230, . 5. - screw out all mixture by 1 turn and half. Make sure you have enough initial spark-somewhere 12-16* I would bet with that cam unless it's way down on compression. stabilize each time, until it starts to decrease. The right one has no affect at all, the left one if ran all the way in will make it stutter but that's about all. Give the idle a few seconds. If I turned one idle mixture screw in, the car would stutter and want to die. Not open for further replies. Mar 5, 2003 · Texas, USA. turning the screws will change the idle speed, thats normal. These tips apply to all Holley carbs from 4150 to 4160 to 4500 series. How do I go about cleaning out that side. Idle mixture affects operation from idle to about 1/8 throttle, so take the screws out about 1 1/4 to 1 1/2 turns from lightly seated. Problem is now I have a surging idle, if I set it below 850-900. $17. Then try to set your mixture screws with a vacuum gauge to obtain the highest vacuum reading at idle for the best idle with your cam. This is an older thread, you may not receive a response, and could be Mar 3, 2009 · 127 posts · Joined 2007. tried a 750cfm carb and the same thing happens, so it tells me the carb isnt the problem. ohidid, Stroker Ace Ventura and J Mark. May 19, 2007 · Increasing idle air bleed size leans the idle mixture by. Hook up a vacuum gauge to fine tune the idle to highest vacuum or use a tach and adjust to highest idle rpm. Back them all off 1 full turn. Set the screw in the position where the engine’s idle sounds most even and smooth to balance the fuel mixture. 10. Backed out all mixture screws 1 1/2 turns. Closed front and rear mixture screws by turning them all the way clockwise. Turn the mixture screws until you achieve the highest vacuum signal at idle. Jan 16, 2017 · I set my mixtures screws with engine off first. Oct 3, 2008 · 1. Get a vacuum gauge, hook it up to manifold vacuum and with the mixture screws run all the way in and then backed out a turn and a half, start on one screw and turn it out until you get the highest vacuum signal on the gauge, then do the same thing on the other screw Dec 11, 2011 · Set the primary blades so only a square is showing on the transfer slot. Jun 26, 2021 · Adjust the idle speed screw so that about 1/32 of the transfer slot is exposed (. If the idle jetting is okay, the idle mixture screws should ideally be about one turn out, although 1/2 to 11 ⁄2 turns is acceptable. 18 deg. Your engine was running with too much throttle, you need to close it down. video. I blew @ 40psi into the holes and put my hand over the rag ontop of the carb so it did'nt blow off. Do this until you get the smoothest idle and the vacuum meter stays steady. If your Holley carburetor is equipped with four idle mixture screws, the procedure will be exactly the same except that the additional two screws will receive the same attention. Jun 3, 2010 · To set idle mixture screws: 1. 5-7 PSI of fuel pressure. If I adjust screws in to get into high 12s to mid 13s idle becomes rough, low 14 screws 1/4 turn out and idles real bad. Ignition timing set to 10* for now. Spray carb cleaner in the "holes" with the small tube that you attatch to the spray nozzel working the tube in and out as you spray 4. The carbs are an Edelbrock 750 and a Holley 735 - both vacuum secondaries. So one of my idle mixture screws does not change the idle at all, and the other side kills the engine when it is screwed in too far. On my 600 cfm Holley carb (4160 converted to a 4150) the idle screws have little to no affect on the idle. Next, back them out 1 full turn and restart the engine making sure the choke is completely off 6. Your carburetor may have two or four mixture screws. reducing the pressure drop across the idle air bleeds. the car idles at about 900 rpm for the most part, any lower will cause it to stall. If you look closely, you will see a hole underneath each transfer slot. I have a Holley 600 on my mild 400 smallblock chevy. ~10:1 compression. 6 rockers. I do not have vaccum gauge. I tried this the other day. Some cleaning and adjustments usually solve the problem. More fuel in the system is rich, more air in the system is lean. Jun 15, 2006 · For a start adjust the primary side to show about 20 thousandths of the transition slot. It sits on top of a Mercury 390 engine in my old '58 Ford truck. Aug 25, 2008 · First make sure the idle transfer slots on front and rear are squared up then adjust your 4 corner mixture screws. Holley. Turning the mixture screws in (clockwise Aug 10, 2018 · Car was running weird, un-even idle, almost stalling. 003) or so . When I adjust the idle mixture screws to highest vacuum, 21 inches in park & 19 in gear and smooth clean idle, I'm at 10. I can get a steady "idle" at 1100 rpm but if I drop it below that it wanders all over the place. There are holes below the transfers slots (and below the throttle plates) that the idle mixture screws control. 5:1 in park and 14. Controlled by the idle mixture screws. The next step will be to set the idle mixture. Oct 10, 2003 · STBR Discussion starter. Fights using the idle mixture screws too. 030” IJ. Jul 17, 2005 · idle mixture screws not working. 3. The idle speed screw on the linkage opens and closes the butterfly for optimum RPM. K. The longer explanation is the idle circuit feeds both the transfer slot and then the idle mix screws which control fuel to the idle port. And the screws DO control idle mixture, That is the only variable. Location. Transition slot is good, power valve is good Mar 3, 2009 · 127 posts · Joined 2007. Are you running any PCV, since you might need the additional air from the crankcase, to allow the throttle blades to close down. Jan 16, 2017 · Re: Holley mixture screws. Pay attention to their position and back them out two full turns. begins. #3. In a 4150 like a 750 with a 3/16” T-slot that would give a very rich mixture screw. I've read many threads on this forum pertaining to this issue and followed the advice therein, but Feb 25, 2015 · February 27, 2015, 12:25 PM. Mar 28, 2015 · It instantly stalled. 039 to . Dec 3, 2009 · The best way to adjust the idle mixture screws on any carb is with a Good Vacuum gage. Get the engine up to temp 2. Hello guys I had another post on my quick fuel carb running so rich it would not idle without smoke out the pipes. Total timing, all in by 2900 rpm. Yup, the secondaries are feeding fuel even on non-four-corner-idle carbs. Mar 24, 2020 · Chris, start with the carb at 1/2 turn open from closed throttle for the speed screw, 1 - 1. By ear. Back off the idle speed screw (not the mixture screw) until the throttle is closed completely, then screw it in a half turn. This procedure is only used on engines with large duration camshaft that have very low vacuum at idle. Pa. Primary metering block IFR . The vacuum reading actually goes up a little. Sep 2, 2005 · that why it's rich even with the screws all the way out. #1 · Oct 10, 2003. Jul 23, 2007 · Sounds like you're dealing with multiple problems. Other brands and some older carburetors will require a sight plug removed to check this. I run 36 degrees total timing. Feb 9, 2016 · If so, you may be running lean at cruise. A bunch of tinkering later, I have it running with the secondaries closed some more, and the primaries open some more. This should get you carb back on the idle circuits and off the transition circuit. 4. Ray. 14 posts · Joined 2003. Feb 3, 2008 · Motor Oil Madman, It's actually VERY simple to do mixture screws on a Holley. Make sure your primary throttle blades are Nov 11, 2015 · Normally, a Quick Fuel Technology carburetor will have the fuel level half-way up the sight window with 6. #1. STEP-4: Run the Engine. Nov 23, 2022 · The most common issues with Holley carbs are flooding and incorrect fuel/air mixture. Also when you turn the screws about a 1/2 Jan 6, 2018 · I have 4160 Holley (1850-3) to be exact. Initial timing, W/O vac adv, (55 deg with vac adv @ idle) Hooked up to manifold vac (15 inHg @ idle) 32 deg. From this point you can lean it by clockwise turns, or rich by counterclockwise. Were assuming this is a cam problem. #4 · Oct 13, 2023. For complete details click anywhere in this block. The same conditions can be created by backing out the idle mixture. Recheck the front idle mixture after the rear setting has been set. 078 primary idle air bleed . Fuel should just barely trickle out of the sight hole at idle. Out, lean. Carb is set to factory Holley specs. (Way lean stall to way rich) See if this gets you back on the ball field. Then slowly tighten up the idle screw until you see the pencil and sticky tab start to move (meaning you are now opening the primaries). I have a mild cam XE262. Corvette/Holley "tri-power" end carbs also have fully-functional but non-adjustable idle circuits. 65 primary jet 68 secondary. Holley 1850 Carb List #80457-2. Turn the engine on and allow it to idle. 480 . Weiand xcellerator low rise intake. Good luck. I've been tuning on my Holley and I can't seem to figure it out. May 21, 2019 · It drops down to 2 holes, the outter hole supplies fuel to the idle mixture screw, the inner hole is for the transition circuit. by rally » Fri Dec 16, 2011 1:01 pm. Go back and repeat the process, fine tuning the idle mixture and repeat the process for a third and final time. Fire it up and get the engine warm and then see if the idle speed ends up where you need it with a clean mixture screw setting. To properly set the idle, you have to endure several iterations of going back and forth between these adjustments until you get it right. Any more and mixture gets rich, while loosing vacuum. Started it up, still running funny. Most racing carburetors will have either 8 or 12 air bleeds depending on whether they are 2 or 3 circuit. Sep 14, 2009 · No more than 0. When the engine RPM or vacuum drop, the idle mixture is too lean and the mixture screws will need to be backed out to the highest vacuum or RPM. I set my mixtures screws with engine off first. Based on that I have seen some article where it is mention to do following step: - with engine off. Z. Feb 25, 2012 · Feb 25, 2012. You have insufficient privileges to reply here. That hole is what the mixture screw affects. Some carburetors have a reverse idle adjustment (some 2300, 4150 and 4160 Holley carbs, for example). (2) Estimated to ship direct from manufacturer on 05/22/24, pending manufacturer availability. Screw in until engine starts to stall or stumble, back out 1/2 turn. How to properly adjust the secondary speed screw on Holley carbs. Mar 9, 2016 · Idle issue with holley 4160. 040” IAB and . 025 high speed air bleed primary and secondary. I suppose this indicates that there's air leak somewhere in that carb. Slowly tightened (clockwise) each mixture screw by 1/8th turn until manifold vaccum pressure was around 10 on the attached vaccum pressure gauge. there's two ways for the PV to leak, one is though a hole or crack in the diaphragm and the other is when the front of the main body isn't flat, some are low around the PV chamber and let fuel leak in from the main circuits. May 22, 2024 · 4. While driving, it would "dog" when I stepped on the gas, then catch up with itself. Then you are at optimal idle mixture. As said before set the timing first, make sure you have no vales leaking or adjusted to tight. 08-25-2008 #10. Aug 7, 2022 · I'm setting up the four corner idle adjustment mixture screws on my Holley carburetor. This is a new carb that sat with fuel in it for about 5 years. I'm going to add that the idle mixture screws meter the gas not the air, so turning them in would lean out the mixture as it would limit the amount of fuel entering the idle air bleed passage that goes to the transfer slots. the cam is a comp cams 280H, 280 duration, and . Reduce the engine idle speed and repeat the process until the engine idles at the desired rpm. To set idle speed without resorting to the stonehenge method of drilling holes in the primary plates - Holley has this little screw that adjusts the secondary throttle blades (see below). Fire up engine, and adjust accordingly. First of all the carb is the original one but it is not new. I called quick fuel and they said it has to be run as a 4 corner idle so I got a secondary metering block put on with idle mixture screws and put some idle air bleeds the same Jan 23, 2004 · C3 Tech/Performance - Holley 850 DP idle mixture screws - I added a Holley secondary idle adjustment screw to my 850. You have something going on with your carb. Sep 14, 2020 · It seems that I'm getting too much fuel in with my mixture as I'm blowing black smoke. A good start is too turn them all in, back off a 1/2 turn, hook up your vacuum gauge, start with the front drivers side and go clockwise adjusting for the most vacuum. which tells me that it is bypassing the idle circuit. Take your carb off, flip it over, and look at the transfer slots. by rally » Tue Jan 17, 2017 2:09 am. The idle air screws make little difference, they do kill the engine when turned all the way in. Now the butterflies are back on the idle adjustment of the carb. Timing is 15 initial, 35 total. connect a vac gauge and adjust the mixture screws one at a time working around the carb for the highest manifold vac. Example of this is your carb with . It is a 327 SBC from 67' that has a 350 crank in it. Aug 18, 2012 · The more un-seated it is (out) the more air it lets by because the jets thin taper is exposed, just like raising the needle lets more fuel thru. Set Idle Correctly. Aug 5, 2009. Carburetor Installation and Tuning. . Sep 30, 2017 · I rebuilt the Holley and the engine is still running super rich. Realize for 99% of the motors out there the idle air bleeds that holley installed will do Jun 4, 2012 · After this has been done, you can begin adjusting all of the idle mixture screws. Re-torqued the bowls and the carb to manifold bolts to make sure everything was tight. 046. Oddometer: 77. While at idle, back them out 1/8 turn at a time May 22, 2024 · Holley Idle Mixture Screw Gaskets Cork. Take precaution make sure that you keep fuel away from any ignition source. carburetor tuning and adjustments. - Start then engine and adjust idle speed if needed. The cam is a little above stock but nothing radical. turn while you're watching the vacuum gauge. It was a little difficult as I had a total of 8 idle mixture screws. 600 CFM 1460 holley carb. This might seem way too simple, but for a carbureted street engine this is the most important tuning step you can make because street engines spend a majority of their time Apr 18, 2007 · Apr 18, 2007. 048 secondary idle air bleed (2 corner idle) . If I close the mixture screws entirely, the black smoke disappears (although I see some very faint smoke), but even 1 turn out the black smoke returns. Try pulling your vac advance to reduce the timing at idle and idle it back up with the idle screw. Apr 30, 2020. Are you sure the power valve is not blown or to high of a opening point. Feb 14, 2009 · 68 posts · Joined 2007. Most Holley four-barrels only use idle mixture screws on the primary side, but more and more performance carburetors use what is called a four-hole idle with mixture screws on the secondary side as well. I'm also running a descent size cam and that is making the tuning difficult. That is a good starting place for the idle screw. This allows me to adjust the secondary idle from the top of the carb, without having to pull it off and adjust it from the bottom. 049 size and Mar 7, 2019 · Pick one idle mixture screw and call it "number 1”. The only way to obtain the highest vacuum, and get my 383 stroker to run its best, is to have all four idle mixture screws turned out a half of a turn. As I understand it, these carbs should be anywhere from 3 - 5 turns out from bottomed as a typical mixture. You may need to reset the idle mixture screws and repeat the process. Oct 15, 2012 · Its one of the Smog Holley's that just changed how much AIR the Idle circuit sees , Normal Holley's adjust the TOTAL mixture with air AND fuel , so turning it all the way in Leans the mixture ( Opposite of what a Vacuum leak would show ) , so in other words its a tad RICH , NOT Lean , still I bet its just on the verge , Id drop Main Jets down 3 numbers and readjust , also check for a leaky May 29, 2009 · However, I have been having the suspesion its very rich by the horrible smell it can make. Apr 30, 2020 · 14,904. Screw in all the way very carefully until they bottom out. I have read on here you should be able to turn both the mixture screws all the way in and the engine should die. 060 of the slot should be showing when the throttle is it the idle position. This should lean it out a bit, If you will notice, most production cars idle around 5 - 10 deg BTDC because it allows the throttle plates to be open Aug 6, 2003 · Unknown member Discussion starter. Could be a huge vacuum leak or clogged idle passages, wrong gaskets, dirty carb, etc etc. Dec 2, 2009 · 1 2. Turn the mixture screws, alternating between the two in 1/4 turn at a time until the engine rpm starts to drop, then Feb 17, 2021 · This example uses a typical Holley four-barrel 750 cfm vacuum secondary carburetor with two idle mixture screws. 982 posts · Joined 2009. Turned both mixture screws all the Dec 10, 2020 · Turn each screw out a bit for a start (maybe 1 turn). My car ran like hell and was barely able to idle, but it was ideling. Oct 13, 2023 · 7576 posts · Joined 2004. Open up your mixture screws to about 1. Aug 16, 2011 · If you don't use that throttle blade setting, the transfer doesn't work right and hesitations abound. The center carb is adjustable. Learn More. After all of the idle mixture screws have been adjusted Mar 4, 2008 · The idle mixture screws don't do a thing - even when screwed in all the way. However as you said, you've got too much fuel pressure which can cause the same problem as Eddy carbs don't like anything over 5 psi. 350 sbc. I have a good 13. Timing isnt my problem, its all in the fuel area with a over enriched fuel circuit. The true test will be trying the ZL-1 Carb. Also, if your idle mixture screws are to lean you will get a bad hesitation regardless of accelerator pump cam selected. Then, place a pencil, eraser side down, in to the primary side of your carb so the eraser is sitting on the butterfly valve. A helpful hint: All of the vacuum readings on the vacuum gauge should be the same May 30, 2013 · For the initial adjustment, all idle screws should be within 1/4-turn of each other, although you may have to turn the primary screws out an additional 1/8 to 1/4-turn. Jan 11, 2021 · We often see idle mixture screws wildly different from side to side. Well I got new engine installed an fired up. I rev it in the driveway, snap it open, slowly accelerategreat! Maintains a 14:1 all the way to 1500 or so. Put the carb back on. Feb 13, 2012 · When the idle goes up, idle it down on the idle speed adjustment to the given cam, likely around 700 rpm. So, if you turn the air screw OUT it will let more air in, thus causing it to be lean. Starting adjusting your mixture screws 1/8 of a turn at time clockwise. Count the number of turns out from the seated point for all four screws. Then fine tune the idle with the primary. kt. Jan 27, 2009 · Holley Idle mixture screw help. The air going into the engine is constant at idle. #2 · Mar 3, 2009. This holley carburetor has four corner idle adjustment and I'm going t That way you only have to adjust your primary idle adjustment in very small amounts. Put a sticky tab on the point end of the pencil. I have a holley 600 cfm vaccum secondairy carb on my 302 in my mustang. 54. as far as the screws, with the engine off turn both screws clockwise until they are all the way in. xvytwvietkqpuimtugnc
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