I used your advice on Idle air bleeds to get my idle speed down to where I wanted it and also get it leaned out enough to let my mixture screws work correctly on my old 750 DP with a Chinese billet base plate (did the same mods to it that you did on yours). I got some solid 6-32 brass inserts and drilled them out bigger than the existing holes by 4-5 thousanths at first. I drilled and tapped the old idle air bleed holes out and tapped them for 6-32 - it wasn't too hard. Then I kept opening up the idle air bleed holes until I got it where I wanted it. Don't forget to debur the drilled hole edges on the brass inserts. This made an old beat up 750 DP come alive again! Thanks for the advice Randy!
I’ve followed you for a couple years now and you are such a knowledge of info to us guys who still run carbs on our classics. This here video is exactly what I did for my big crammed SBC to not only stop the “rich” tears in my idle eyes - but throttle response is awesome. Just to tell you guys new to Randy’s carb knowledge - get an air/fuel mixture gauge to help you with this fine tuning (AINT cheap at $150 but so worth the time saved) and you’ll be able to actually SEE what your motor likes. Thanks again Randy - I speak for all of us you’ve educated with your time and knowledge.
Randy + Camera Guy: VERY glad to see you guys uploading again. I decided to go pick up a 4781-8 (850 Mech. Sec.) to restore just for something to tinker with in the evenings. Although I know my way around a Holley pretty good, I ALWAYS learn something from your videos. What do y'all prefer to use as a carb dip? Berryman's? Thank You.
I'm trying to remember who I ordered it from can't recollect brand. I have an old safety kleen air operated carb cleaning machine works great with almost any cleaner it induces air bubbles an agitates. I'm sure Berrymans will work fine. Happy to be back and thanks.
@@holleycarbshowtosadvice40y90 best vid for this ever, easy to understand. Do you have an email? When I go through mine any help you gave Id be happy to pay you for, Or just send it to you
Just found your channel recently - lots if great info to go through. Just starting to tinker with a Holley 670 Street Avenger carb on a mild 383 Chevy just acquired. Look forward to seeing more from you!
Hello Randy, another great video. If I may, it's always a good practice to have some fuel discharge through the transition slot at idle, so that as you open the throttle, fuel inertia will reduce the possibility of a lean condition, which then would have to be corrected. During the 60s and on, we would drill 1/8" holes in the throttle plates, positioning the holes so as to make a triangle with the throttle plates screws. Thanks for the privilege to comment. By the way, I wish I could give hands on help, pro bono, to some of the young men that are involved in racing. At Bailey Tech in St Louis I was able to help my students. Regards!
Bert sorry it took so long to get back to you, I use my transfer slots at idle too. There is a well known builder out there that closes up his t slots at idle. I rebuilt one his carbs that to many people had been in, and a very unusually fuel curve. I corrected the problems and returned it, when the racer installed the carb he called me up told me to listen and cracked the throttle and I was surprised at the throttle response. It worked great even though I had my doubts.I guess you never know, but mine have excellent throttle response too. I have enjoyed the chat, take care my friend.
in this vid you mention (around 2:30 time mark) thatyou have almost closed the transfer slots on some carbs so that virtually all of the idle mixture is controlled by the mixture screws, and it worked fine. can you do a vid on that setup in detail? thanks
This mod requires a lot of time, removing the primary butterflies and throttle shaft and slightly open up the throttle bore. This is more of a custom mod. It so easy to damage a 850 throttle plate. The primary idle speed screw cannot be used to set idle speed, you have to use secondaries idle speed screw or air bypass holes in low engine vacuum conditions. Hope this helps
@HolleyCarbs, ok, thanks much. does this mod improve off idle and low rpm throttle response or what is the resulting performance improvement of this mod. thanks again.
I like the idea of having full control over the idle mixture, but if the carb is tuned right its hard to o say, could be a small advantage. At the same time it can be more trouble to tune.
i left a little out i have a dig-6 ing box , dis is MSD , the only thing that i changed was the carb thinking i would pick up a little more ET and MPH which i did before changing my barry grant for the holley it's one of those idea's that i would do more good than bad and it is a 1/4 mile drag car
Even check throttle opening while manually pressing pedal to the floor, don't overlook anything, double check anything that could be a restriction to the bowl vents. Wish I could be more helpful.
65 stang with 465 cfm Holley 4548, (vacuum secondary). Ran fine. ............. Then rebuilt with 280/290 duration cam and carb ran bad. Edalbrock carbs do work. QUESTION: since 4160 Holleys have metering plates and not blocks, the 4160 carbs can't be adjusted in the way you describe, right?
The early 4160's came with metering blocks. You have to change to a primary metering block for the rear and modify from there.Hope this helps. Ps some idle circuit holes have to be finished drilled, no biggy. Let me know if you need any help. Also the metering block can be from almost any primary 4150 with a few mods. Take care.
@@holleycarbshowtosadvice40y90 thanks. I have a 600 cfm 4160, but it ran worse than the 465. Never thought about using a primary block to replace the secondary plate. I'll look into it. Thanks.
thank you randy, im building a pair of 600 vaccum sec carbs to put on my tunnel ram im sure ill have some ??????????s hope you have the time to help me , thanks again for your time hope your feelin better
May I ask a question? I have a 4 corner idle 750 vac sec pro form holley, how does the secondary throttle blade adjustment(screw under shaft on passenger side) fit into the equation? I've set the primaries transfer slot to square and used the secondary adjustment to adjust the idle🤷 then I KNOW the transfer slot is right. Is that acceptable at all ? Thanks for any response.
I usually will compensate with rear idle adjustment to a point, but with me only to a point because I square everything from air bleeds to jetting. I'm not saying you can't, its just not my way. If it performs well and your happy with it thats all that matters. Hope this helps.
Make sure float levels is set properly, if you crack the throttle and hold it there and if it stays rich, it boils down to where your rpm is if its below booster activation then i would change the idle air bleeds if there changeable go up .003 larger at a time. That will lean idle and transfer slots. Hope this helps.
Wonderful stuff, enjoy watching and learning. Question, is it acceptable on a 4 corner idle carb to have the IFR and/or IAB different size on the front than the rear? On my QF 780vs I have good fuel screw adjustability on the secondarys but not so much on the primarys. I'm thinking of leaning out the front more than the rears to gain some fuel screw adjustment. I'm wondering if the exposed transfer slot, which is adjusted properly, adds more fuel thereby causing my problem.
I have a Holley 600 CFM 1850 carburetor and I can't get it to idle as low as I want (idling at 1000 rpm and I want at 800. Can I completely close the transfer slots? All the videos on this say they need to be a square opening on the slots. Thanks for any advice
When I close off my transfer slots at idle I'm just using the mixture screws to control the idle, I don't think that's going to help you with your idle speed. I would need to know your engine specs and your idle vacuum. I'll try to help.
Hola buen vídeo creo que este video me enfoca más para arreglar el problema de haber comprado un carburador 850 cfm cuando lo que ocupo uno de 650 , saludos
great videos, my issue is with a 4160 600 cfm Holley, it idles fine but as soon as it goes off idle it seems to flood and skip or tremble and stumbles until you accelerate much more or return to curb idle. HELP!!! This is on a 1986 F150 with 351 HO engine Thanks in Advance
First with engine off look down the throat of the primaries to see if the accelerator pump is squirting the minute you move the throttle if its not check accel. Pump adjustment, also remove one of your bowl screws to drain fuel out of primary fuel bowl and check it for water or trash. Hope this helps, let me know if not fixed
I have tried many things to help solve this issue but still stumbles and sounds like a dead skip off idle. Air screw adjustment has no effect on idle speed.
@@holleycarbshowtosadvice40y90 It would take me about an hour of typing to tell you what I have done to to try and fix this issue with the end result the same. Thank you for your reply. The only fix I know to do is replace the carb. Thank you for the great and detailed Holley videos.
If I have a small cam I will use the secondary idle speed screw to compensate for extra air but a medium to large cam or tunnel ram has to have bypass holes to tune properly in my opinion. Hope this helps
@@holleycarbshowtosadvice40y90 My 427 bbc has a Howard's roller, Lift: .578 / .618, Duration @ .050: 231 / 235, Centerline: 108, big enough to drill? Should I start with 1/16 holes?
I appreciate the video, I have a question. I’m running a 1050 dominator 4500 carb on the street on a 496 I built. It’s a 3 circuit Holley setup with an intermediate air bleed circuit in addition to what you talked about in this video. We have been dialing it in we are running a single stage power valve in the primaries with 85 main jets, and 90 in the secondaries no power valve in secondaries. I can’t find any information on them. Or how to tune the intermediates. Looks to be about a .060 orifice in the bleed. I’ve got the setup to run at 14.0 at idle, and 12.7:1 at wot. I’m trying to lean out the part throttle cruise portion. Combo makes about 12in vacuum at idle and about 22in at part throttle cruise I think I may be drawing down on the intermediate circuit hard I’m curious do you go bigger in the bleed to lean it out some? Or do I restrict the emulsion jets some? It’s running a mid 12:1 afr on part throttle cruise?
Hey Randy, I have a Holley Speed Demon 750DP carb that I can't get to drive at low speeds about 20 or 25MPH cruising the neighborhood it goes lean about 20 + AFR. It just falls on its face after squirters are done. I have 13.5 at idle and 14.2 at 60 (3K RPM) cruising. Checked for vacuum leaks with carb cleaner even replaced throttle plate bushing front and back little more slop than I liked in them (thinking air leak). Transition slots are squared front and back when closed also. 4 corner idle. Whats your thoughts, Thanks in advance.
Mike you said you squared your transfer slots, I only square my primaries, i try to keep my secondaries open about like the primaries. You can open the secondaries a little more but don't expose the transfer slots if it needs more air i drill bypass holes. After that you may need to open up your idle fuel restrictor .hope this helps
Not enough info on this. My AED needs tweaking on these bleeds and dont know where to start. WHen warm I go lean esp at idle drives me nuts 850 dp ho series
Always great info! So because I've been too much of a chicken to drill my primaries, I've been cheating it by cracking open the secondaries further (4160 model, vacuum secondary) to compensate. Is this a good idea or bad in many ways...? Subject is SBF dual 390 cfm Holleys on a Weiand Tunnel ram.
No it works fine up to a point and an easy fix for some combinations, but to make a tunnel ram or a camed up race engine work properly it takes more mods. I'm sorry to get so long winded, but when engine vacuum is low yes I drill the butterflies and I'll close up the transfer slots as much as possible without the throttle plates sticking and then tune with idle air bleeds, this is a time consuming repair but it always gives me my best performance I hope this helps and take care.
@@holleycarbshowtosadvice40y90 I guess my reasoning behind not drilling out the primaries was I wasn't completely sold on those carbs and had thoughts of switching to something else with adjustable air bleeds. I didn't want to render these carbs to just this car or that engine. (a new engine was in the works as this one was garbage 8.7:1 with a big cam) Need a more proper build to adequately run a tunnel ram to begin with! Thanks for the info and keep 'em coming!!
You are absolutely right it is tuned more to that type of engine, that engine you described was in trouble from the start lol. Very nice talking to you.
Hi Randy, I have a 750 main body & metering blocks that accept screw in type air bleeds. What size do you think I should start with?(base line) I’m starting from scratch. 70 chevelle 454 comp cam. 4corner ldle & the metering blocks have 4 circuits. Thanks!
I currently have the opposite issue, I am too lean at idle. I currently have a 650 DP, 67/79 jets, .093 drilled throttle plates. Engine is a fairly radical old school small block Ford that only makes 7 inches of vacuum at idle. Even with the .093 throttle plates in all four holes, I can't get enough air with the transfer slots "square". If I crack the rears open a bit more, it will idle but go leaner when I crack the throttle. I can open the fronts some and idle it up, but it is very lean, even when I hold it at 2000rpm or so. Do I need to go even larger on the throttle plate holes?
Dont drill your bypass holes any larger, i need all of your engine build information , i would check your engine for a large vacuun leak, make sure your carburetor idle circuit is not restricted, and your ignition timing is correct, next perform a compression test and write me back your compression readings. 7 inches is just to low . Let me know.
@@holleycarbshowtosadvice40y90 it has always made 7-8 inches of vacuum. .040 over 302, heavily ported Windsor heads, 10.5:1 compression. 230/240, 280/290, .523/.555 lift on a 106lsa. Performer RPM Air Gap with a 2 inch 4 hole spacer. I ran it for years with a 750 5160 with the .093 plates in all four corners and a 4.5 power valve with no issues. I swapped to this 4150 650 and installed the same parts, but it still needs more throttle opening at idle to run, and I can't get enough fuel at idle to make it happy.
@holleycarbshowtosadvice40y90 they are working, but I can steadily back them out to a full three turns and the idle just keeps getting better. At that point it still isn't a clean idle, and I can steadily tap the accelerator pump lightly and the idle gets smoother. Everything points to it wanting more fuel at idle.
Ok lets try this first your idle fuel restrictor controls how much fuel the idle circuit receives, if you have removeable ifrs then increase the size by .005 to .010 larger both ifrs, if there not removeable you can drill them out to see this helps. I have a video on how to drill them out and tap some threads in to make changing them quick. This will increase the amount of fuel to your idle mixture screws. Let me know.
Hey thank's for the reply i put a new fuel pump, fuel line's and new tank . the only thing that was changed was the carb , at the race's a freind let me try his carb and to no surprise the car ran great , it's the carb and only the carb giving me the problem . the engine is 383 cu in, no popping , the ing. system good MSD the wire;s are 8.5 mm MSD cam solid roller comp cam and an auto tran's with all of this it is NOT the motor , all that was changed was the carb ,all it will do is flatten out
I would tear the carburetor down and look closely for any restriction, floats binding, make sure no restriction in the bowl vents or fuel logs, jets , power valve circuit restrictions. Check all bleeds, you might wont to substitute some metering blocks, check boosters for restrictions, I wish I could give you a better answer but if its in the carb thats the only way I know to find it. Also I have seen spring loaded filters in the bowl inlet, tear it totally down. Look at metering block gaskets Hope this helps.
Sir -thank you for your advice it's more than what i have been told, i did take it apart replace all gasket's new float's and needle and seat'sthe only thing that bothers me is the power valve plug in the secandary i was thinking about changing to a regular power valve and was wondering about your advice on that ? . again thank you very much for your advice @@holleycarbshowtosadvice40y90
Carl it should be fine blocked make sure your jets are 6 to 8 jet sizes larger in the secondaries and make sure you have notched floats and jet extensions in the secondaries to prevent starvation. Good luck brother.
Ive got a 2300 that is pig rich at idle, I’ve drilled out the butterflies to 2.8mm but it still runs pig rich and won’t run on the idle circuit. Should I go bigger or is there a problem with fuelling?
First you need to make sure your power valve diaphragm isn't leaking, or you'll never be able to control the idle mixture. I need more information list number of carb and cubic inches and vacuum at idle.let me know, if my carb is in good shape then i set my idle speed and remove my carb and look at the transfer slots if there open over .020 to .030 then I drill larger bypass holes, some 2 barrel combinations I have drilled over .200 it all come down to camshaft size and engine size and carb 2300 could be a 350cfm or 500 cfm. After checking pv then make small changes at a time. Hope this helps. Let me know. One last thing make sure your idle bleeds aren't blocked.
No the secondary transfer slot should be closed at idle, only the primary is exposed and needs to be adjusted And this is due to a racing camshaft that creates a low idle vacuum . Hope this helps
I have a question i hope you could answer i have a ultraXP 850 cfm holley carb , im having a top end problem about the 800 foot mark the motor flattens out even with the pedel to the floor it,s driving me crazy would you have any idea what is going on with this card , it has been wet tested ???????? i put a new fuel pump ,new fuel line,s new fuel tank it did nothing
I need alot of information, and I'll try to help. I take it your racing the 1/4 mile. Engine cu.inch, Ok when the engine flattens out is it popping through the carb or the exhaust, or surging or anything you noticed. The engine flattens at what rpm and is this consistent, I take it this happens in third gear if its auto (trans type). What type of distributor and ignition boxes if any are you running. A stock or HP air cleaner, type of gas tank stock or aftermarket and describe gas tank vent. Is there any rubber line in the fuel system and were. Does the engine rpm well in first and second gear with no flattening and is this consistently happing every time. Also type of ignition coil and wires, type of camshaft hydraulic or solid flat tappet or roller and valve spring pressure ( seat) and over the( nose. )
Hi thank you for advice and time ,i sent replies so i will answer your question's yes i race 1/4 mile the inginion system is all MSD , the coil is the big blue one tran's is automatic the engine is 383cu in fuel system is HP no stock , and i replaced everything ing box is a digital 6 wire's are 8.5 MSD no air cleaner there is no popping or anything out of the header's it run's great 1st and 2nd and 3 rd it's a 4 speed it's about the 800 foot mark where it lay's over i run 6 1/2 pound's of fuel at the carb cam is a comp cam solid roller and yes it happen at the same time every time at the last race a friend let me use his carb and there wasn't an issue it ran like it should of i shift the car at 6800 rpm if you need more info i will give it to you but not much left i did send other replies but don't know if you received them im hoping you might have an answer @@holleycarbshowtosadvice40y90
I need more information about your engine, if you have a performance camshaft, it can effect your primary and secondary idle adjustment,,usually if I need to bypass more air, I will raise my secondary idle speed adjustment.
With your primary transfer slots set properly. Yes you can set your secondaries matching, then set your idle speed with your built in idle air bypass adjustment. Hope this helps
The 67 Corvette Holley (2 idle screws) uses IFR’s measuring .028”, so I stay in the .025” to .029” range more importantly w/4 corner. Favoring .025” IFR & smaller IAB’S. There is a range (IFR/IAB) of air to fuel ratio of around 19:1 area wise that seems to work well. Too big an IAB kills fuel velocity. I find modern Quick Fuel/Holley’s everything is too big. So one needs to recalibrate EVERY ORIFACE (IFR, IAF, PVR, JETS, everything) right out of the box to avoid black spark plugs, overly rich, and stinky exhaust. The transfer slots need to be restricted from .106” down to .081”/.078” because the T slots are too big. I’m talking street use not drag racing. I like your series😊
19 -1 is way to lean , usually they won't even idle at 19-1, if now talking about a stock engine yes it is much easier to figure your fuel curve A typical 4 corner idle circuit you need to limit your ifr size and increase your iab size, now if you add a racing cam you have to bypass enough air to correct your transfer slots and then you work with your ifr and iab . Hope this helps.
Thanks for all the great videos
I appreciate it!
Thank you very much.
I used your advice on Idle air bleeds to get my idle speed down to where I wanted it and also get it leaned out enough to let my mixture screws work correctly on my old 750 DP with a Chinese billet base plate (did the same mods to it that you did on yours). I got some solid 6-32 brass inserts and drilled them out bigger than the existing holes by 4-5 thousanths at first. I drilled and tapped the old idle air bleed holes out and tapped them for 6-32 - it wasn't too hard. Then I kept opening up the idle air bleed holes until I got it where I wanted it. Don't forget to debur the drilled hole edges on the brass inserts. This made an old beat up 750 DP come alive again! Thanks for the advice Randy!
This is great information. Thank you.
Good to have you back, great content like always
Thanks Scott
I’ve followed you for a couple years now and you are such a knowledge of info to us guys who still run carbs on our classics.
This here video is exactly what I did for my big crammed SBC to not only stop the “rich” tears in my idle eyes - but throttle response is awesome.
Just to tell you guys new to Randy’s carb knowledge - get an air/fuel mixture gauge to help you with this fine tuning (AINT cheap at $150 but so worth the time saved) and you’ll be able to actually SEE what your motor likes.
Thanks again Randy - I speak for all of us you’ve educated with your time and knowledge.
Thank you for watching my friend.
So glad to see you back and thank you
Glad to help .
I'm watching your vids over and over. I'm working on mine as I go
Ok
I'll try to help you any way i can.
Randy + Camera Guy: VERY glad to see you guys uploading again.
I decided to go pick up a 4781-8 (850 Mech. Sec.) to restore just for something to tinker with in the evenings. Although I know my way around a Holley pretty good, I ALWAYS learn something from your videos.
What do y'all prefer to use as a carb dip? Berryman's?
Thank You.
I'm trying to remember who I ordered it from can't recollect brand. I have an old safety kleen air operated carb cleaning machine works great with almost any cleaner it induces air bubbles an agitates. I'm sure Berrymans will work fine. Happy to be back and thanks.
@@holleycarbshowtosadvice40y90 best vid for this ever, easy to understand. Do you have an email? When I go through mine any help you gave Id be happy to pay you for, Or just send it to you
another good one.
Just found your channel recently - lots if great info to go through. Just starting to tinker with a Holley 670 Street Avenger carb on a mild 383 Chevy just acquired. Look forward to seeing more from you!
Thank you.
Thank you guys, always good too see your videos:)
Thanks mike
Your knowledge is invaluable thank you
Thank you .
Hello Randy, another great video.
If I may, it's always a good practice to have some fuel discharge through the transition slot at idle, so that as you open the throttle, fuel inertia will reduce the possibility of a lean condition, which then would have to be corrected.
During the 60s and on, we would drill 1/8" holes in the throttle plates, positioning the holes so as to make a triangle with the throttle plates screws.
Thanks for the privilege to comment.
By the way, I wish I could give hands on help, pro bono, to some of the young men that are involved in racing. At Bailey Tech in St Louis I was able to help my students.
Regards!
Bert sorry it took so long to get back to you, I use my transfer slots at idle too. There is a well known builder out there that closes up his t slots at idle. I rebuilt one his carbs that to many people had been in, and a very unusually fuel curve. I corrected the problems and returned it, when the racer installed the carb he called me up told me to listen and cracked the throttle and I was surprised at the throttle response. It worked great even though I had my doubts.I guess you never know, but mine have excellent throttle response too. I have enjoyed the chat, take care my friend.
in this vid you mention (around 2:30 time mark) thatyou have almost closed the transfer slots on some carbs so that virtually all of the idle mixture is controlled by the mixture screws, and it worked fine. can you do a vid on that setup in detail? thanks
This mod requires a lot of time, removing the primary butterflies and throttle shaft and slightly open up the throttle bore. This is more of a custom mod. It so easy to damage a 850 throttle plate. The primary idle speed screw cannot be used to set idle speed, you have to use secondaries idle speed screw or air bypass holes in low engine vacuum conditions. Hope this helps
@HolleyCarbs, ok, thanks much. does this mod improve off idle and low rpm throttle response or what is the resulting performance improvement of this mod. thanks again.
I like the idea of having full control over the idle mixture, but if the carb is tuned right its hard to o say, could be a small advantage. At the same time it can be more trouble to tune.
@HolleyCarbs ok, thank you very much for your informative responses.
i left a little out i have a dig-6 ing box , dis is MSD , the only thing that i changed was the carb thinking i would pick up a little more ET and MPH which i did before changing my barry grant for the holley it's one of those idea's that i would do more good than bad and it is a 1/4 mile drag car
Even check throttle opening while manually pressing pedal to the floor, don't overlook anything, double check anything that could be a restriction to the bowl vents. Wish I could be more helpful.
Thank you Randy every little bit help's@@holleycarbshowtosadvice40y90
65 stang with 465 cfm Holley 4548, (vacuum secondary). Ran fine. ............. Then rebuilt with 280/290 duration cam and carb ran bad. Edalbrock carbs do work.
QUESTION: since 4160 Holleys have metering plates and not blocks, the 4160 carbs can't be adjusted in the way you describe, right?
The early 4160's came with metering blocks. You have to change to a primary metering block for the rear and modify from there.Hope this helps. Ps some idle circuit holes have to be finished drilled, no biggy. Let me know if you need any help. Also the metering block can be from almost any primary 4150 with a few mods. Take care.
@@holleycarbshowtosadvice40y90 thanks. I have a 600 cfm 4160, but it ran worse than the 465. Never thought about using a primary block to replace the secondary plate. I'll look into it. Thanks.
thank you randy, im building a pair of 600 vaccum sec carbs to put on my tunnel ram im sure ill have some ??????????s hope you have the time to help me , thanks again for your time hope your feelin better
Mike I'll be glad to help, just let me know brother.
May I ask a question? I have a 4 corner idle 750 vac sec pro form holley, how does the secondary throttle blade adjustment(screw under shaft on passenger side) fit into the equation? I've set the primaries transfer slot to square and used the secondary adjustment to adjust the idle🤷 then I KNOW the transfer slot is right. Is that acceptable at all ? Thanks for any response.
I usually will compensate with rear idle adjustment to a point, but with me only to a point because I square everything from air bleeds to jetting. I'm not saying you can't, its just not my way. If it performs well and your happy with it thats all that matters. Hope this helps.
@@holleycarbshowtosadvice40y90 yes sir it helps a lot! I appreciate the response and your videos. They have helped me tremendously
Thank you.
Great videos! What if idle is all good but as soon as you crack the throttle on light cruise it richens up considerably?
Make sure float levels is set properly, if you crack the throttle and hold it there and if it stays rich, it boils down to where your rpm is if its below booster activation then i would change the idle air bleeds if there changeable go up .003 larger at a time. That will lean idle and transfer slots. Hope this helps.
@@holleycarbshowtosadvice40y90 thanks a lot! I Will give that a try.
Wonderful stuff, enjoy watching and learning. Question, is it acceptable on a 4 corner idle carb to have the IFR and/or IAB different size on the front than the rear? On my QF 780vs I have good fuel screw adjustability on the secondarys but not so much on the primarys. I'm thinking of leaning out the front more than the rears to gain some fuel screw adjustment. I'm wondering if the exposed transfer slot, which is adjusted properly, adds more fuel thereby causing my problem.
Yes ive set up carbs with different primary and secondary iab .
Good video thanks for the info.👍🏻
Glad to help.
Love the info
Thanks
I have a Holley 600 CFM 1850 carburetor and I can't get it to idle as low as I want (idling at 1000 rpm and I want at 800. Can I completely close the transfer slots? All the videos on this say they need to be a square opening on the slots. Thanks for any advice
When I close off my transfer slots at idle I'm just using the mixture screws to control the idle, I don't think that's going to help you with your idle speed. I would need to know your engine specs and your idle vacuum. I'll try to help.
Hola buen vídeo creo que este video me enfoca más para arreglar el problema de haber comprado un carburador 850 cfm cuando lo que ocupo uno de 650 , saludos
English only
Need to adjust my carburetor I have very rich idling issues
Make sure your power valve not leaking.
How do I contact you for service in the Jacksonville area?
I'm not doing any service work right now only advice. Would be glad to answer any questions. Lord willing I'll be doing service work in the future.
great videos, my issue is with a 4160 600 cfm Holley, it idles fine but as soon as it goes off idle it seems to flood and skip or tremble and stumbles until you accelerate much more or return to curb idle. HELP!!! This is on a 1986 F150 with 351 HO engine
Thanks in Advance
First with engine off look down the throat of the primaries to see if the accelerator pump is squirting the minute you move the throttle if its not check accel. Pump adjustment, also remove one of your bowl screws to drain fuel out of primary fuel bowl and check it for water or trash. Hope this helps, let me know if not fixed
I have tried many things to help solve this issue but still stumbles and sounds like a dead skip off idle. Air screw adjustment has no effect on idle speed.
Let me know what you have tryed to repair it
@@holleycarbshowtosadvice40y90
It would take me about an hour of typing to tell you what I have done to to try and fix this issue with the end result the same. Thank you for your reply. The only fix I know to do is replace the carb. Thank you for the great and detailed Holley videos.
Instead of drilling a hole in the throttle blades to adjust the idle, can you open up the secondary throttle blades on a 750 double pumper?
If I have a small cam I will use the secondary idle speed screw to compensate for extra air but a medium to large cam or tunnel ram has to have bypass holes to tune properly in my opinion. Hope this helps
@@holleycarbshowtosadvice40y90 My 427 bbc has a Howard's roller, Lift: .578 / .618, Duration @ .050: 231 / 235, Centerline: 108, big enough to drill? Should I start with 1/16 holes?
I appreciate the video, I have a question. I’m running a 1050 dominator 4500 carb on the street on a 496 I built. It’s a 3 circuit Holley setup with an intermediate air bleed circuit in addition to what you talked about in this video. We have been dialing it in we are running a single stage power valve in the primaries with 85 main jets, and 90 in the secondaries no power valve in secondaries. I can’t find any information on them. Or how to tune the intermediates. Looks to be about a .060 orifice in the bleed.
I’ve got the setup to run at 14.0 at idle, and 12.7:1 at wot. I’m trying to lean out the part throttle cruise portion. Combo makes about 12in vacuum at idle and about 22in at part throttle cruise I think I may be drawing down on the intermediate circuit hard I’m curious do you go bigger in the bleed to lean it out some? Or do I restrict the emulsion jets some? It’s running a mid 12:1 afr on part throttle cruise?
If its an air bleed larger will lean, if you will send me your list number, I'll try to help.
Hey Randy, I have a Holley Speed Demon 750DP carb that I can't get to drive at low speeds about 20 or 25MPH cruising the neighborhood it goes lean about 20 + AFR. It just falls on its face after squirters are done. I have 13.5 at idle and 14.2 at 60 (3K RPM) cruising. Checked for vacuum leaks with carb cleaner even replaced throttle plate bushing front and back little more slop than I liked in them (thinking air leak). Transition slots are squared front and back when closed also. 4 corner idle. Whats your thoughts, Thanks in advance.
Mike you said you squared your transfer slots, I only square my primaries, i try to keep my secondaries open about like the primaries. You can open the secondaries a little more but don't expose the transfer slots if it needs more air i drill bypass holes. After that you may need to open up your idle fuel restrictor .hope this helps
Not enough info on this. My AED needs tweaking on these bleeds and dont know where to start. WHen warm I go lean esp at idle drives me nuts
850 dp ho series
Give me all your carb information in detail, (everything) and engine info. Explain all your symptoms.
Always great info!
So because I've been too much of a chicken to drill my primaries, I've been cheating it by cracking open the secondaries further (4160 model, vacuum secondary) to compensate. Is this a good idea or bad in many ways...? Subject is SBF dual 390 cfm Holleys on a Weiand Tunnel ram.
No it works fine up to a point and an easy fix for some combinations, but to make a tunnel ram or a camed up race engine work properly it takes more mods. I'm sorry to get so long winded, but when engine vacuum is low yes I drill the butterflies and I'll close up the transfer slots as much as possible without the throttle plates sticking and then tune with idle air bleeds, this is a time consuming repair but it always gives me my best performance I hope this helps and take care.
@@holleycarbshowtosadvice40y90 I guess my reasoning behind not drilling out the primaries was I wasn't completely sold on those carbs and had thoughts of switching to something else with adjustable air bleeds. I didn't want to render these carbs to just this car or that engine. (a new engine was in the works as this one was garbage 8.7:1 with a big cam) Need a more proper build to adequately run a tunnel ram to begin with! Thanks for the info and keep 'em coming!!
You are absolutely right it is tuned more to that type of engine, that engine you described was in trouble from the start lol. Very nice talking to you.
Hi Randy, I have a 750 main body & metering blocks that accept screw in type air bleeds. What size do you think I should start with?(base line) I’m starting from scratch.
70 chevelle 454 comp cam. 4corner ldle & the metering blocks have 4 circuits. Thanks!
Is your emulsion circuit adjustable?
@@holleycarbshowtosadvice40y90 yes. Billet aluminum aftermarket block.
I need to know how many emulsion holes and what brand block
@@holleycarbshowtosadvice40y90 Deepmotor
Manufacturer Part Number DM-1110MB.
Thanks again for your time & support!
I'll have you a fuel curve tomorrow.
Can you do a video on the 4412’s for dirt track racing?
Yes I can, is your class allowed to modify or bend the rules lol. What size track.
Hey Randy do you have a shop or a fb page? I’m in dyer needs of some tuning advice on my sbf.
Look me up on fb under Randall Cribb
I currently have the opposite issue, I am too lean at idle. I currently have a 650 DP, 67/79 jets, .093 drilled throttle plates. Engine is a fairly radical old school small block Ford that only makes 7 inches of vacuum at idle. Even with the .093 throttle plates in all four holes, I can't get enough air with the transfer slots "square". If I crack the rears open a bit more, it will idle but go leaner when I crack the throttle. I can open the fronts some and idle it up, but it is very lean, even when I hold it at 2000rpm or so. Do I need to go even larger on the throttle plate holes?
Dont drill your bypass holes any larger, i need all of your engine build information , i would check your engine for a large vacuun leak, make sure your carburetor idle circuit is not restricted, and your ignition timing is correct, next perform a compression test and write me back your compression readings. 7 inches is just to low . Let me know.
@@holleycarbshowtosadvice40y90 it has always made 7-8 inches of vacuum. .040 over 302, heavily ported Windsor heads, 10.5:1 compression. 230/240, 280/290, .523/.555 lift on a 106lsa. Performer RPM Air Gap with a 2 inch 4 hole spacer. I ran it for years with a 750 5160 with the .093 plates in all four corners and a 4.5 power valve with no issues. I swapped to this 4150 650 and installed the same parts, but it still needs more throttle opening at idle to run, and I can't get enough fuel at idle to make it happy.
Are your mixture screws leaning and richening the mixture , or do your mixture screws have no effect on your idle?
@holleycarbshowtosadvice40y90 they are working, but I can steadily back them out to a full three turns and the idle just keeps getting better. At that point it still isn't a clean idle, and I can steadily tap the accelerator pump lightly and the idle gets smoother. Everything points to it wanting more fuel at idle.
Ok lets try this first your idle fuel restrictor controls how much fuel the idle circuit receives, if you have removeable ifrs then increase the size by .005 to .010 larger both ifrs, if there not removeable you can drill them out to see this helps. I have a video on how to drill them out and tap some threads in to make changing them quick. This will increase the amount of fuel to your idle mixture screws. Let me know.
Hey thank's for the reply i put a new fuel pump, fuel line's and new tank . the only thing that was changed was the carb , at the race's a freind let me try his carb and to no surprise the car ran great , it's the carb and only the carb giving me the problem . the engine is 383 cu in, no popping , the ing. system good MSD the wire;s are 8.5 mm MSD cam solid roller comp cam and an auto tran's with all of this it is NOT the motor , all that was changed was the carb ,all it will do is flatten out
I would tear the carburetor down and look closely for any restriction, floats binding, make sure no restriction in the bowl vents or fuel logs, jets , power valve circuit restrictions. Check all bleeds, you might wont to substitute some metering blocks, check boosters for restrictions, I wish I could give you a better answer but if its in the carb thats the only way I know to find it. Also I have seen spring loaded filters in the bowl inlet, tear it totally down. Look at metering block gaskets Hope this helps.
Sir -thank you for your advice it's more than what i have been told, i did take it apart replace all gasket's new float's and needle and seat'sthe only thing that bothers me is the power valve plug in the secandary i was thinking about changing to a regular power valve and was wondering about your advice on that ? . again thank you very much for your advice @@holleycarbshowtosadvice40y90
Carl it should be fine blocked make sure your jets are 6 to 8 jet sizes larger in the secondaries and make sure you have notched floats and jet extensions in the secondaries to prevent starvation. Good luck brother.
Ive got a 2300 that is pig rich at idle, I’ve drilled out the butterflies to 2.8mm but it still runs pig rich and won’t run on the idle circuit. Should I go bigger or is there a problem with fuelling?
First you need to make sure your power valve diaphragm isn't leaking, or you'll never be able to control the idle mixture. I need more information list number of carb and cubic inches and vacuum at idle.let me know, if my carb is in good shape then i set my idle speed and remove my carb and look at the transfer slots if there open over .020 to .030 then I drill larger bypass holes, some 2 barrel combinations I have drilled over .200 it all come down to camshaft size and engine size and carb 2300 could be a 350cfm or 500 cfm. After checking pv then make small changes at a time. Hope this helps. Let me know. One last thing make sure your idle bleeds aren't blocked.
What is a suitable fuel pressure to run on a Quick Fuel 750 with vacuum secondarys?
6 psi
Does the secondary transfer slot need to be adjusted the same way as the primary transfer slot?
No the secondary transfer slot should be closed at idle, only the primary is exposed and needs to be adjusted
And this is due to a racing camshaft that creates a low idle vacuum . Hope this helps
@@holleycarbshowtosadvice40y90 Thanks
I have a question i hope you could answer i have a ultraXP 850 cfm holley carb , im having a top end problem about the 800 foot mark the motor flattens out even with the pedel to the floor it,s driving me crazy would you have any idea what is going on with this card , it has been wet tested ???????? i put a new fuel pump ,new fuel line,s new fuel tank it did nothing
I need alot of information, and I'll try to help. I take it your racing the 1/4 mile. Engine cu.inch, Ok when the engine flattens out is it popping through the carb or the exhaust, or surging or anything you noticed. The engine flattens at what rpm and is this consistent, I take it this happens in third gear if its auto (trans type). What type of distributor and ignition boxes if any are you running. A stock or HP air cleaner, type of gas tank stock or aftermarket and describe gas tank vent. Is there any rubber line in the fuel system and were. Does the engine rpm well in first and second gear with no flattening and is this consistently happing every time. Also type of ignition coil and wires, type of camshaft hydraulic or solid flat tappet or roller and valve spring pressure ( seat) and over the( nose. )
Hi thank you for advice and time ,i sent replies so i will answer your question's yes i race 1/4 mile the inginion system is all MSD , the coil is the big blue one tran's is automatic the engine is 383cu in fuel system is HP no stock , and i replaced everything ing box is a digital 6 wire's are 8.5 MSD no air cleaner there is no popping or anything out of the header's it run's great 1st and 2nd and 3 rd it's a 4 speed it's about the 800 foot mark where it lay's over i run 6 1/2 pound's of fuel at the carb cam is a comp cam solid roller and yes it happen at the same time every time at the last race a friend let me use his carb and there wasn't an issue it ran like it should of i shift the car at 6800 rpm if you need more info i will give it to you but not much left i did send other replies but don't know if you received them im hoping you might have an answer @@holleycarbshowtosadvice40y90
Do you open your secondaries on a double pumper as far as the primaries?
I need more information about your engine, if you have a performance camshaft, it can effect your primary and secondary idle adjustment,,usually if I need to bypass more air, I will raise my secondary idle speed adjustment.
434 small block with .577 lift and 242/248 duration. Dual plane manifold, Holley Ultra HP 850 with 14 in. vacuum at idle. Thanks.
With your primary transfer slots set properly. Yes you can set your secondaries matching, then set your idle speed with your built in idle air bypass adjustment. Hope this helps
The 67 Corvette Holley (2 idle screws) uses IFR’s measuring .028”, so I stay in the .025” to .029” range more importantly w/4 corner. Favoring .025” IFR & smaller IAB’S. There is a range (IFR/IAB) of air to fuel ratio of around 19:1 area wise that seems to work well. Too big an IAB kills fuel velocity. I find modern Quick Fuel/Holley’s everything is too big. So one needs to recalibrate EVERY ORIFACE (IFR, IAF, PVR, JETS, everything) right out of the box to avoid black spark plugs, overly rich, and stinky exhaust. The transfer slots need to be restricted from .106” down to .081”/.078” because the T slots are too big. I’m talking street use not drag racing. I like your series😊
19 -1 is way to lean , usually they won't even idle at 19-1, if now talking about a stock engine yes it is much easier to figure your fuel curve A typical 4 corner idle circuit you need to limit your ifr size and increase your iab size, now if you add a racing cam you have to bypass enough air to correct your transfer slots and then you work with your ifr and iab . Hope this helps.
Thks
Anytime
Man I got a lot to learn
You know I'm an older guy but I still find new mods that excite me. You'll pick this up with ease. Take care Will.