Well dip me in GUMOUT!!! After all these years, and hundreds of articles on Holley carbs, it FINALLY CLICKED. I have been seeing the main well action BACKWARDS! As rpm increases the float level in the BOWL stays relatively level, the MAIN WELL drops even with the power valve. Exposing more air bleeds as it drops. Air and fuel loop back up to the booster discharge port. I wasn't expecting that bell to go off but it did. DING!
All these videos have been truly educational to me! I have already had success in tweaking my carbs. Drilling the butterflies are next to close the transfer slot and take more control with idel screw adjustment. Wideband meter on the way and I look forward to tackling the next steps! Great Stuff!
This is the kinda stuff I've been looking for. I'm wanting to set my fuel curve from idle to cruise as well as WOT. I found a little in books, but this is so much better. Thanks.
I just stumbled over this video, interesting. FYI, Holley, as well as Weber and other manufacturers used air bleeds in order to achieve the proper flow curve of a carburetor, in order to deliver the proper A/F mixture to the engine. For that reason they are called "air bled carburetors". Carter carburetors (Edelbrocks) on the other hand, use metering rods to achieve specific flow curves. I worked as an R&D Engineer at Carter and trained Auto-Diesel Technology for 35 years. People don't realize how easy and yet how complex it can be for someone to explain how a carburetor works. Technical as well as air and fluid dynamics are a plus. I've had the opportunity to watch some of the videos on RUclips and sometimes I wish I could jump in and help the narrator with proper terminology and functionality, in order to make the video more precise. Keep up the good work! God bless!
I bought some .028" blanks from Amazon, bought 2 sets of drill bits so I could make anything from .028 up to an unrealistic size. There is a trade off, I am unable to make a couple sizes like .033" is one, but it's an air bleed it can be "close enough" until I get the wideband air fuel ratio meter. Thank you Randy I always enjoy this videos, helped me loads tuning my lil s10
Clean your idle circuit with Guage pins and check for proper size, and disassemble and clean complete circuit, hope this helps , if you don't have Guage pins you can substitute torch tip cleaners as a last resort ,be careful with em.
Good video for learning. I thought he would use a drill vise for drilling. Did not know the air bleeds were blanks that required drilling. Do you use a pin gauge to determine size?
Measure twice drill once ,You just have to be careful when drilling and tapping for fuel restrictors and air bleeds.Somtimes you can repair some ,others are throw away.
So i screw my idle mixture screw all the way in and the idle picks up and my air fuel guage goes fat 10 - 11 Does that mean I have dirty air bleeds or a bad power valve or both ( idle mixture screws in it should stall) not pick up
Carl a blown power valve diaphram will cause this, and if the transfer slots are too far open this will also cause this problem I Have video's on the transfer slot's and how to adjust them , under holley tuning mods for high duration cams idle circuit.
If you oversized, made the system too lean, the bleeds and replace the static orifices with tubes coming out of the carb... Connected the tubes to quarter turn or half turn valves, couldn't the AFR be adjusted externally?
If i drilled the offices to big then I would tap threads in the main body and install my air bleeds in the main body. That way you can change your air bleeds as many times as nessasary. Hope this helps
Thanks for posting ALL your videos.My original intent was to build a 750 with an 850 throttle plate as you mentioned in an earlier video modifications would have to be done to the 850 throttle plate to accomplish this.Correct me if I'm wrong but you have not made that video of those modifications yet correct ? I still would like to see how to perform those modifications but got so wrapped up in the 650 build I started a 650 build first .Getting ready to use the flapper wheel to enlarge the bottom of the main body bores to the 750 size gasket.I watch your videos over and over to let it all sink in !
could I change the air fuel ratio at different throttle positions by using different imulsion jets? the scenario I have is with my truck when it comes to towing. my throttle position when I'm cruising while towing something is quite a bit richer than when I'm cruising with no load. this scenario is without the power valve opening.
My friend i don't know what year truck you have , but unless its very old your not allowed to change emissions legally. Now a drag strip track car you can change fuel mixture with emulsion circuits and high speed air bleeds in combo with jetting and power valve, when pulling a load I'm always sure I have a air fuel ratio guage hooked up making sure I'm not to lean or engine damage can occur. Hope this helps, good luck. Ps make small changes.
@holleycarbshowtosadvice40y90 no, it didn't really answer my question. I was wondering if the emulsion jets will effect the AFR at different throttle positions when cruising. I do have an afr gauge, and yes, it's an old farm truck that we haul stuff hay and other heavy loads with from time to time.
I replaced the boosters , was informed by Holley if I drill and tap main body fit screw in air bleeds it will ruin it ? Was also told by replacing boosters from straight to down it won’t work because of the circuit
Dont believe everything you hear, holley dont have any problems putting annular or straight boosters or step down boosters in a holley, I not telling you to do it , just showing you what I do , I have 50 years of experience , you have to under stand how a fuel curve works and everybody that modifies carbs , has a fuel curve of his own.
Hello. My car has a 4778-c idles at around 12.9 has a 70 main 75 secondary. 6.5 vacuum and it runs 10 at anything more than 1/4 throttle. What do I do?
Blake I'll need more information , like the type of carb , size of carb and rpm this happens , does it hesitate or surge , also is it automatic or stick shift and year of truck and size of motor.
@@holleycarbshowtosadvice40y90 Brawler 600cfm, electric choke, vacuum secondary. 350 chevy crate L31 vortec heads bone stoke. 87 chevy pickup with 4 speed. Tbi to carb swap. Installed AFR gauge and noticed lean condition when i try to lug the truck down below 1200 rpm. I am running a larger cam on the primary acc pump (blue) Looking for more low speed performance as the truck is a woods truck and i do alot of slow idling.
@@holleycarbshowtosadvice40y90 been using Holley carbs for 25 years. Screwing round with jets and shooters, 50cc pumps, pump cams etc. But, at the end of the day, if it's working good stop screwing with it!! Running 750 vacuum secondary on the street with 50cc pumps and 31-33 shooters to bandade it to drive daily! All to keep from running a double pumper on an daily driver! Bet drilling out the bleeds would've went a long way! Who knew back then! But it worked pretty good! Milled off choke horn is a bitch in the winter! Thanks for the tip, gonna build a 351w for my 94F150 flareside. I'll run a carb down here!
@@holleycarbshowtosadvice40y90 they look great, but you'd have to have a 3500-4000 stall! I'd like a turbo with 10 psi. Gotta rum on 93, that's pushing it. By the time you pull enough timing out!! Reality sucks!!
My issue is that my AF is reading 13 at cruse 45-60 running mains @ 65 when I push my throttle down just a tad my AF jumps to 15-16 so is seems to want more air, I don't understand why it is rich down hill and leaner on a grade...????
I need some more info. Are you running a manual or automatic transmission? Whats your engine c.i? What are the specs on your holley, for instance whats your holley list number, what power valve size and main jets? If you will reply with the information, I'd be glad to help you! -Randy
I am running a 4150 750 VS , my engine is a BB 396 it is professionally built balanced and blue printed with Edelbrock RPM Perfomer head's and matching RPM dual plane intake it's cam is a comp roller cam roller rockers 1500 -5800 .. as I said I have 65 mains from 72s and 76 rear from 78s the plugs are running a beautiful tan color, but I believe that the AF at a soft Cruse should be 14 .7 to 16 at a lean Cruse??? I don't have air bleeds that are threaded but I am willing to drill them out to a size that I am not sure of ??? I have the bits for my drummel... Thank you
This engine is not going to perform well at 14.7. 1. That lean flat spot is before the power valve is comes in, you can check the pv opening with your af meter and a vacuum guage, you'll have to time the pv opening at the lean spot, or you might try a two stage pv. Hope this helps.
I have 4.5 power valve. 33 idle air bleeds. 77 main jet. 84 jet sec.Just got jet kits to day. Work on tomorrow. Just don't know what I should change .. air bleeds or jets. If I hold throttle down to about 2000 rpm.afr gage reads 12.5.then leans out from there.
It'd be nice to have a completely see-through carburetor..to see how all these orifices collaborate together and what makes changes and how it affects things.. put it on a flow bench draw vacuum through the carburetor and watch what happens... Where the fuel goes where the air comes from..why hasn't somebody made a see-through carburetor so we can actually watch this stuff work..🤔
Thank you so much for making this simple for dummies like me to understand how a carburetor works
I hope you can use this information.
Well dip me in GUMOUT!!! After all these years, and hundreds of articles on Holley carbs, it FINALLY CLICKED. I have been seeing the main well action BACKWARDS! As rpm increases the float level in the BOWL stays relatively level, the MAIN WELL drops even with the power valve. Exposing more air bleeds as it drops. Air and fuel loop back up to the booster discharge port. I wasn't expecting that bell to go off but it did. DING!
It really makes sense once you think about it, I love leaning new things too.
@@holleycarbshowtosadvice40y90 me to...keeps the brain sharp.
As a geezer trained on carburetors in the early ’80s I’m pretty damn impressed with this guy …UTG guys should add to subs
I'm another old geezer I trained in the early 70s hope you enjoyed.
All these videos have been truly educational to me! I have already had success in tweaking my carbs. Drilling the butterflies are next to close the transfer slot and take more control with idel screw adjustment. Wideband meter on the way and I look forward to tackling the next steps! Great Stuff!
Thank you.
Very interesting I have always liked to rebuild and mess with carbs Thank You. !
Your welcome
This is the kinda stuff I've been looking for. I'm wanting to set my fuel curve from idle to cruise as well as WOT. I found a little in books, but this is so much better. Thanks.
Thank you
Very good information and much appreciated. I hope you will continue to share your knowledge. Thank you
Thank you
Thanks, Randy. I always look forward to your videos.
Thank you for watching
I just stumbled over this video, interesting.
FYI, Holley, as well as Weber and other manufacturers used air bleeds in order to achieve the proper flow curve of a carburetor, in order to deliver the proper A/F mixture to the engine. For that reason they are called "air bled carburetors". Carter carburetors (Edelbrocks) on the other hand, use metering rods to achieve specific flow curves.
I worked as an R&D Engineer at Carter and trained Auto-Diesel Technology for 35 years.
People don't realize how easy and yet how complex it can be for someone to explain how a carburetor works. Technical as well as air and fluid dynamics are a plus.
I've had the opportunity to watch some of the videos on RUclips and sometimes I wish I could jump in and help the narrator with proper terminology and functionality, in order to make the video more precise.
Keep up the good work! God bless!
I'll do my best thanks.
Thanks! Nice vid.. Been installing Holley carbs for many years but never seen someone explain like you..
Thanks
great work
Thanks
I bought some .028" blanks from Amazon, bought 2 sets of drill bits so I could make anything from .028 up to an unrealistic size. There is a trade off, I am unable to make a couple sizes like .033" is one, but it's an air bleed it can be "close enough" until I get the wideband air fuel ratio meter. Thank you Randy I always enjoy this videos, helped me loads tuning my lil s10
You are most welcome
Excellent!
Thank you.
U make ME understand... Thank man, videos are great !!
You are very welcome, thank you.
You a good teacher.
Learn something new
Thanks.🌄😁
You are most welcome,thank you.
Great explanation.
Thanks
Great video!
Thank you
Awesome answer. In was asking my self what those multiple holes in aftermarket metering block where doing...👌
Thanks for watching
Lay that part 3 on us!! 🍻🍻
Thank you for explaining it
Your welcome.
Waiting waiting ))
Clean your idle circuit with Guage pins and check for proper size, and disassemble and clean complete circuit, hope this helps , if you don't have Guage pins you can substitute torch tip cleaners as a last resort ,be careful with em.
👍
You been talking to Saxon right?
Love your videos. Do you have a video showing how to add 4 corner idle circuit to a 4150DP
Jus go to my you tube page , converting a 2 circuit holley to a 4
Good video for learning. I thought he would use a drill vise for drilling. Did not know the air bleeds were blanks that required drilling. Do you use a pin gauge to determine size?
Yes
Awesome video. You make it look too easy. What do you do if you drill too far on the counter sink part of the idle bleeds?
Measure twice drill once ,You just have to be careful when drilling and tapping for fuel restrictors and air bleeds.Somtimes you can repair some ,others are throw away.
good vid.
Thanks.
So i screw my idle mixture screw all the way in and the idle picks up and my air fuel guage goes fat 10 - 11
Does that mean I have dirty air bleeds or a bad power valve or both ( idle mixture screws in it should stall) not pick up
Carl a blown power valve diaphram will cause this, and if the transfer slots are too far open this will also cause this problem I Have video's on the transfer slot's and how to adjust them , under holley tuning mods for high duration cams idle circuit.
Keep bringing the videos! I've got a dual quads tunnel ram on a 289, so got air of tuning to learn and do.
I also have dual quads on on a sbc 350 - this has helped me a lot already.
Glad I could help.remember think out of the box.
Hey randy were can i get the air bleeds from.
I can't remember, I believe your local speed shop or summit racing. I'm going to try to get you some more information.
If you oversized, made the system too lean, the bleeds and replace the static orifices with tubes coming out of the carb... Connected the tubes to quarter turn or half turn valves, couldn't the AFR be adjusted externally?
If i drilled the offices to big then I would tap threads in the main body and install my air bleeds in the main body. That way you can change your air bleeds as many times as nessasary. Hope this helps
Thanks for posting ALL your videos.My original intent was to build a 750 with an 850 throttle plate as you mentioned in an earlier video modifications would have to be done to the 850 throttle plate to accomplish this.Correct me if I'm wrong but you have not made that video of those modifications yet correct ? I still would like to see how to perform those modifications but got so wrapped up in the 650 build I started a 650 build first .Getting ready to use the flapper wheel to enlarge the bottom of the main body bores to the 750 size gasket.I watch your videos over and over to let it all sink in !
There is mods to the idle circuit and fitting the main bore to the 850 throttle plate.
could I change the air fuel ratio at different throttle positions by using different imulsion jets?
the scenario I have is with my truck when it comes to towing. my throttle position when I'm cruising while towing something is quite a bit richer than when I'm cruising with no load. this scenario is without the power valve opening.
My friend i don't know what year truck you have , but unless its very old your not allowed to change emissions legally. Now a drag strip track car you can change fuel mixture with emulsion circuits and high speed air bleeds in combo with jetting and power valve, when pulling a load I'm always sure I have a air fuel ratio guage hooked up making sure I'm not to lean or engine damage can occur. Hope this helps, good luck. Ps make small changes.
@holleycarbshowtosadvice40y90 no, it didn't really answer my question. I was wondering if the emulsion jets will effect the AFR at different throttle positions when cruising.
I do have an afr gauge, and yes, it's an old farm truck that we haul stuff hay and other heavy loads with from time to time.
I replaced the boosters , was informed by Holley if I drill and tap main body fit screw in air bleeds it will ruin it ? Was also told by replacing boosters from straight to down it won’t work because of the circuit
Dont believe everything you hear, holley dont have any problems putting annular or straight boosters or step down boosters in a holley, I not telling you to do it , just showing you what I do , I have 50 years of experience , you have to under stand how a fuel curve works and everybody that modifies carbs , has a fuel curve of his own.
Hello. My car has a 4778-c idles at around 12.9 has a 70 main 75 secondary. 6.5 vacuum and it runs 10 at anything more than 1/4 throttle.
What do I do?
Charles I don't understand what your asking me .I need more information and how it's effecting engine porformance.
Love your videos! Where are you from?
Jacksonville FL.
Any idea why i get a lean condition when I'm lugging my truck around? What circuit would that be?
Blake I'll need more information , like the type of carb , size of carb and rpm this happens , does it hesitate or surge , also is it automatic or stick shift and year of truck and size of motor.
@@holleycarbshowtosadvice40y90
Brawler 600cfm, electric choke, vacuum secondary.
350 chevy crate L31 vortec heads bone stoke.
87 chevy pickup with 4 speed.
Tbi to carb swap.
Installed AFR gauge and noticed lean condition when i try to lug the truck down below 1200 rpm. I am running a larger cam on the primary acc pump (blue)
Looking for more low speed performance as the truck is a woods truck and i do alot of slow idling.
Any thoughts on this
Liked the video! Been considering buying a Proform
Thanks for watching, let me know if I can help.
@@holleycarbshowtosadvice40y90 been using Holley carbs for 25 years. Screwing round with jets and shooters, 50cc pumps, pump cams etc. But, at the end of the day, if it's working good stop screwing with it!! Running 750 vacuum secondary on the street with 50cc pumps and 31-33 shooters to bandade it to drive daily! All to keep from running a double pumper on an daily driver! Bet drilling out the bleeds would've went a long way! Who knew back then! But it worked pretty good! Milled off choke horn is a bitch in the winter! Thanks for the tip, gonna build a 351w for my 94F150 flareside. I'll run a carb down here!
If the gas wasn't so high I would be driving a tunnel ram around! Lol .
@@holleycarbshowtosadvice40y90 they look great, but you'd have to have a 3500-4000 stall! I'd like a turbo with 10 psi. Gotta rum on 93, that's pushing it. By the time you pull enough timing out!! Reality sucks!!
Hey you just have to love racing!!!!!
My issue is that my AF is reading 13 at cruse 45-60 running mains @ 65 when I push my throttle down just a tad my AF jumps to 15-16 so is seems to want more air, I don't understand why it is rich down hill and leaner on a grade...????
I need some more info. Are you running a manual or automatic transmission? Whats your engine c.i? What are the specs on your holley, for instance whats your holley list number, what power valve size and main jets? If you will reply with the information, I'd be glad to help you! -Randy
I am running a 4150 750 VS , my engine is a BB 396 it is professionally built balanced and blue printed with Edelbrock RPM Perfomer head's and matching RPM dual plane intake it's cam is a comp roller cam roller rockers 1500 -5800 .. as I said I have 65 mains from 72s and 76 rear from 78s the plugs are running a beautiful tan color, but I believe that the AF at a soft Cruse should be 14 .7 to 16 at a lean Cruse??? I don't have air bleeds that are threaded but I am willing to drill them out to a size that I am not sure of ??? I have the bits for my drummel... Thank you
This engine is not going to perform well at 14.7. 1. That lean flat spot is before the power valve is comes in, you can check the pv opening with your af meter and a vacuum guage, you'll have to time the pv opening at the lean spot, or you might try a two stage pv. Hope this helps.
My afr gage reads 10.8/ 11.5 at idle.and if I rev it up it goes lean 22.off gage what can I try to fix.
I need more information.
I have 4.5 power valve. 33 idle air bleeds. 77 main jet. 84 jet sec.Just got jet kits to day. Work on tomorrow. Just don't know what I should change .. air bleeds or jets. If I hold throttle down to about 2000 rpm.afr gage reads 12.5.then leans out from there.
It'd be nice to have a completely see-through carburetor..to see how all these orifices collaborate together and what makes changes and how it affects things.. put it on a flow bench draw vacuum through the carburetor and watch what happens... Where the fuel goes where the air comes from..why hasn't somebody made a see-through carburetor so we can actually watch this stuff work..🤔
Don i believe ( blp ) bo laws performance might have a video showing at lest part of the carb in a see through state.