You are tuning my blow through turbo carb for me thanks. I have it closer to perfect each time I watch your videos. Thanks for sharing such valuable information, truly pure gold.
Hello Randy thankyou for all these videos and info, also helping me with all my questions when my health is back to normal and the doctor signs me off to get back to working them i sm definitely going to test all these out .
Perfect timing on this video. I have one of those 600 CFM summit racing Holley 4010 carbs. It always ran great except I had a lean spot in the transfer slot area of the carb no accelerator pump tuning could ever take care of. During the summer the engine ran rich enough from the extra heat it wasn't really noticeable, but during the winter it was pretty bad at times if I was cruising at slow speeds and stepped on the gas slightly to accelerate more. I enlarged the Idle fuel restrictor jets from the stock .046" to .049" and totally cured the off idle stumble and made a world of difference in how it runs overall.
@@holleycarbshowtosadvice40y90 Another thing I noticed is before it took about 1.5-1.75 turns from seated on the idle mixture screws to obtain a 13:1 idle AFR and after enlarging the IFR jets now the idle mix screws are at about 1 turn out from seated to obtain 13:1 idle afr.
With respect to the transfer slot, most literature i've read say .020 , so thats exactly where i set my primary throttle blades on my Holley Street Avenger 770 carburetor, and with that, i set the idle at a healthy 800rpm on a ZZ4 crate engine, but i did have to close the secondary throttle plates completely to acheive that. Currently running with the unmodified main body, unmodified front and rear metering blocks and unmodified base throttle plate, IAB(.060), IFR(.033), PVCR(.060), antisyphoning(.028) and emulsion(.028). Its been known the SA line of carburators run leaner because its a street carburetor and not a performance one, but when i compared it to my spare, late 90s 3310-2 carburetor i have, front metering block only, all the orifices are exactly the same size(+/- .01) everwhere, unless its a later revised version of the SA770. If you are familiar, would you care to shed some light on that because i thought the orifices would provide totally different AF mixture ratios due to the design with different models, other than that, so far, so good, all i can do for now is read the plugs(mr43lts), gapped .040 , the porcelain stays white with a dark tan ring on the threaded portion, no AFR meter in use yet to properly tune the carb/engine, but thats next on my list. Thanks
Thats fine , you can set it at .010 if you want to. What this means is most of your idle mixture will be controlled through the idle mixture screws, now on a race car its different , it matters what your doing with the car racing or street driving.
There is so many ways of designing a fuel curve for instance holleys new ultra 750 dp, the high speed air bleeds are .036 and emulsion holes are .029, main jet size is76s. What I'm trying to explain is your jetting changed on this carb do to high speed air bleed and emulsion also the differences between venturi size and throttle plate size has a big influence on the type of curve you can run, if you run a small venturi and you increase your throttle plate size that carb will have to be jetted down because venturi air speed will increase. There is so many different fuel curves, also the ultra holley has a adjustable air bypass which is a nice feature. Hope this helps.
Hey Randy I wanted to ask you one more thing please & if you can give me your opinion & expertise on this. If I were to do the 750 main body mod to the 850 baseplate but use a 2 corner idle baseplate would I still have to do the modification on all 4 corners of the main body or just on the primary side? Let me know please & thanks. Also keep continuing to bring that knowledge to us we're just loving it man.
Hi Randy Have you done a video on what changing the idle air bleeds do and also how the high speed air bleeds work ? I have a 650DP on a 351C The blades were already drilled and I’m just not as happy with it as I think I should be, I’m thinking it might be better without the butterfly’s being drilled. Had a 750DP without holes and it ran beautifully but it’s much more responsive with the 650. Would the drilled blades have anything to do with this ?? Best regards from Australia. Great job on your content 👍🏽👍🏽👍🏽
Aaron drilling bypass holes is mainly for engines with high duration cams, where vacuum is lower than normal at idle, this bypasses air past the throttle plates which helps clean the idle mixture up, but I don't know if you have a hp cam. Give me your engine specs and explain what problems your having and I'll try to help.
@@holleycarbshowtosadvice40y90 Hi Randy. My Clevo is 60 overbore. Manual toploader 4spd It’s a 214/224 @ 50 16 degrees of advance at idle 34 total. It runs great but idles high. Around 800/900 once fully warmed up.
Hello Randy i do have a question regarding boosters if you dont mind answering please. What is the best booster for fuel economy tuning if i have a mild 351 clevland small port dual plane rpm preformer 2 600 cfm 1850 with no exsaught cross over and a 1.5 inch 4 hole spacer ? Thankyou
I believe the annular booster has the best signal, holley use to make a holley economiser carburetor just for good gas mileage, it had a unusual modified type of annular booster, looking at the top of the booster it was star shaped. They performed well and improved mileage. I believe Bolaws performance sells all kinds of annular boosters , look on there website. They may be listed as BLP or Bo laws performance, there in south florida . I'm not sure but I believe lots of small holes in a annular booster might be the trick. hope this helps. Also thank you for your contribution.
I have a proform 750.. on a hot 360 SBC...run rich at idle...idle mixture screws are out only 1/2 a turn ,any more then that car will stall from being way to rich...I believe I need bigger air bleeds.. am I correct.. transfer slots are about closed...put a bigger cam in it and now it's really rich....at idle....I mean really rich...any suggestions.?...70 front jet..81 back.. Dropped from 74 n 84 helped .. 6.5 power valve..... May drop to 4.5 . PV..... maybe drop to 65 front jet n 75 back ..not sure if that's to small or ok....car is 3,400 lbs,,,runs 11:20 @118 MPH..1/4 Mile..488 gear,,on 31-18.5 x 15 tier....pro street car.78 Grand LeMans.... thanks for any help.....
Ok if your sure the transfer slots are right, next check for a leaking power valve, changing the power valve to a different opening or closing number will not help because the pv flows through the boosters and has no effect on the idle circuit ,unless the diaphragm is leaking then it will run extremely rich at idle. A blocked air bleed will make it run rich. Also make sure float level is correct. I would change the power valve first and then as a last resort try a bigger idle air bleed. Hope this helps.
Frank if you have pin gauges check pv restrictions and emulsion holes and idle circuit, change jets I believe they will be close enough. Hope this helps.
Question,it’s unrelated but what is the best way to refinish an old carb and parts that have no finish or is it needed without sending them to Holley?love your info
@@holleycarbshowtosadvice40y90 ok it was early or late but I forgot to also ask with that question and I apologize for taking your time cause I meant to ask if it is indeed necessary?it is a 3310-1 and in great condition other than the coating only needing a final cleaning to complete.jegs screwed up a carb yrs ago and gave me a new one 3310 also but 4160 this is the original body 4150 am again I am sorry
Hey randy , I have a question , my engine only runs if I’m dumping fuel with the throttle , won’t idle and stay running, engine is dual 1050 qft on a high rise tunnel ram , she fires off but won’t stay running .
William if it will stay running with you working the accelerator arm by hand then its lean, look for vacuum leak if nothing is found then check your idle circuit, open your mixture screws up counter clock wise, either out of adjustment or stopped up idle circuit or vacuum leak, most common causes. Hope this helps.
Awesome video! Quick question. This is my current setup on a 500 hp 383 650 speed demon, 22° initial and 36° total. 66 jets , 85 sec. 7.5" pv ifr is 0.030" pvcr is 0.067" iab is 0.076" Hsab is 0.0425" squirters 37/35 It idles great, and the afr is perfect (cruise 13.9:1 and Wot is 13:1) Only issue is that if I slowly slowly give it some throttle at around 2000 or so rpm, it slowly ramps to 16:1 afr, and then goes back to normal. If I get on the gas like normal, it'll be normal. When it leans out slightly like that, it almost sounds like it wants to lean stumble, but it doesn't stumble. There's no load on the engine at that point, but what do you think?
It’s an issue with the wrong size power valve hg for the vacuum at part throttle. You don’t specify, does this happen in gear or idle etc? Manual trans: divide your idle vacuum by 2 to get a base PV hg. Automatic subtract 2 from the engine vacuum at idle in gear to get a base PV hg. *** Drive the vehicle and see if it smooths out the transition from the idle circuit to the main circuit. Adjust up or down 1hg from base to get perfect.
@@HeadFlowInc this is in gear driving at low 2000 rpms, with a manual tranny and 4.11 gears. I'm not talking about pv. I wouldn't even consider this as part throttle. I have a 7.5" pv I have 4.5" Vac at idle. If I put in a 2.5" or a 3.5" pv like you just recommended, I would get way less fuel then if I were to leave the 7.5" pv. I forget what Vac I have at around 2000 rpms, but I would say maybe 12" or 13". A 2.5" would never ever open with the slightest throttle input. So little throttle that I don't even think that the accelerater pump is pumping (I have it set right). Original ifr was 0.033" Would going from 0.030" to a 0.031" or 0.032" ifr, or maybe 0.076" iab to a 0.073" iab work? I need a tad more fuel with a touch of throttle input. There is no load on the engine, so no matter what power valve I used (even blocked off) it shouldn't do that.
Jake its hard to run a engine with that much camshaft lean, you could try going to a .035 ifr or a 68 main jet or both , may have some luck changing to a annular style booster, I think you have done well to get to where your at with such a radical engine.
@@holleycarbshowtosadvice40y90 Yeah it is close now.... Running a 68 jet would then richen up my 3000 cruise. 3000 cruise is still a bit rich but ok at around 14:1 . I would like 15:1 but with my huge cam, it doesn't enjoy 15:1. My throttle is opened so little at 3000 cruise, that I'm mostly on t-slot I think. That's why I'm reluctant to open up the ifr or close up the iab. Since the iab is easy to change, I'll probably close it up to 0.073", and see what happens. Thanks
Is there a way I can contact you. I have a Holley HP series 750. Same mods have been done. And I'm idling fat at one turn out . But if I close it more I have that lean stumble. I have to get my gauge pins in there but it's a pretty sizeable restriction. I got this carb from a friend. Low speed cruise it breaks up alot . I assume I'm still pulling from the idle side .
Hey randy I’ve tried adjusting mixture screws and restricting the idle fuel restrictor , my wide band still registers 12:8 at idle ,,, curious how you would approach this issue ?
Darrin try bigger idle air bleeds, don't restrict your idle circuit under .035 , the bigger idle air bleeds will let you pull more air. As you go up with the idle bleeds the mixture screws will come out further.
The irf should be in the lower facory spot. The idle afr is more consistent under the fuel level. I have fixed more drive ability and idle problems on the newer carbs by moving the ifr down.
Moving the ifr will not cause any driveability concerns, I have changed a thousand of them,the only thing it effects is the restart of the engine at idle if the engine cools down it needs a little accelerator pump squirter to start and thats because there is unmetered fuel setting above the lower mounted ifr the best place is in the high position , the fuel is entering the ifr right in the air bleed steam which gives better emulsion of the fuel and air. Hope this helps.
If that were true, why did all the engineers at holley back in the 70's put them in the bottom. Submerged ifr goes all the way back to ww1 aircraft carburetors. It's in the naca 49 paper from 1919. Locating the Idle Jet below float level is more important than many people realize because cruising at a low RPM and steady speed the fuel delivery is nearly 100% through the idle circuit (T-slot), and, because intake vacuum oscillates rapidly over a wide range, with the jet above float level the AFR oscillates a lot, as much as 2 AFR or more. Smooth idle, clean sparkplugs and oil, and good fuel economy, all depend on a consistent idle-low speed circuit.With a high (above float level) idle jet, air can easily get upstream behind the jet when the idle fuel is pushed backwards by the pulsing. When the jet is submerged, the air cannot get back upstream of it as easily because the much greater viscosity of the liquid fuel (than air) on both sides of the jet impedes the backflow and the air cannot get back through the jet unless the flow is reversed for a longer period of time than the frequency of the pulsations.
Bud you can run it either way, but saying this has caused driveability concerns is wrong, it will have better air fuel emulsion at the top. Holley started putting all there nice performance carbs with high mount ifr years ago plus the ifr are changeable screw in and out restrictors . You have way over thought the idle fuel restrictor and it will work either way your choice. Hope this helps.
Randy, How do we contact you? I have a Mighty Demon 750 that is kicking my butt and I think you are not far from me. I'd like to have you go through it. I've been working on it but can't get it right. Need some new eyes on it.
Butch look at the throttle plate gasket, it is so easy to put the wrong gasket on and it will block the outer idle circuit passage. I feel sure that will fix it, but if you still have a idle problem let me know. Hope this helps.
I can’t agree on the upper IFR on a street car with a reasonable street cam. A smaller IFR lower position will flow more consistently below fuel level, it’s pure science. Most todays (quick fuel) are upper. Changing to lower IFR allows for smaller hole and eliminates the dead rich black spark plugs. Again street car mild reasonable build.
Is the actual IFR the brass incert size or is there a hole underneath the brass insert ?? I have 2 carburetors one is a 600 that has the incerts at the bottom and 1 is for a 670 that has them on top looking down in the holes of IFR i can"tsee any small hole underneath . I have a micro drill bit set from size #50 to 70 #66 is .035. The brass hole is in the 50"s
Most holleys have a brass insert on each side of power valve, a small cutout that has two holes. One is to the main well and the other usually has a brass insert feeding the idle circuit that is the ifr, now if there is no brass insert , than look at the top left or right of metering block and there should be a screw in replaceable idle fuel restrictor. Usually .035 is close. There are some 600 cfm that have idle tubes inside the metering block that is all most lmpossible to take out without damaging the tube or the block itself , in this case i find some metering blocks that have the brass inserts. Hope this helps.
@@holleycarbshowtosadvice40y90 Thanks for the reply on my 600 block I see the IFR at the bottom one brass incert is missing but the hole inside the brass is way bigger than 0.35 it"s probably in the 40-45 size. The sweet spot on my AFR is 12:50 in drive if I try to go to 13:00 or above it acts up and idle quality is trash I'm using full manifold vacuum if I used ported I can go way leaner on the idle circuit but I guess that's why they started to use ported . As far as tuning for highest vacuum I start out at 1.5 turns out and I end up turning the right side in for higher vacuum but the left side wants out ? For higher vacuum I'm thinking of buying the pro form standard purple block so at least I can try different sizes . Funny thing about the 670 SA block it won't run at a idle it was super Rich in the 10 on my AFR gauge I jetted it down only 64 is the Lowest jet I had made no difference it would run on the accelerator pump but once let off it would be super Rich and not want to run at all at 1.5 turns out that 670 block has no emulsion holes at all a on the well like the other blocks do and small holes up top the IFR are on the bottom and smaller than the 600 size .
I don't know if I'm missing something but I understand about 0.31 0.33 0.35 etc in example of the pump squirter size holes . I have a micro drill bit set #61 to# 80 # 64 is 0.35 putting that in the IFR hole i can move it side to side ? Not sure why other carbs need to be drilled out and the ones I have are bigger than the average 🐻 bear . Unless we're talking 650 and up have smaller IFR ?
You are tuning my blow through turbo carb for me thanks. I have it closer to perfect each time I watch your videos. Thanks for sharing such valuable information, truly pure gold.
Thank you for watching.
Awesome video there Randy you do a great job of explaining all the intricacies of the carbs thank you Sir
You are very welcome Mike
Hello Randy thankyou for all these videos and info, also helping me with all my questions when my health is back to normal and the doctor signs me off to get back to working them i sm definitely going to test all these out .
Thank you .
Perfect timing on this video. I have one of those 600 CFM summit racing Holley 4010 carbs. It always ran great except I had a lean spot in the transfer slot area of the carb no accelerator pump tuning could ever take care of. During the summer the engine ran rich enough from the extra heat it wasn't really noticeable, but during the winter it was pretty bad at times if I was cruising at slow speeds and stepped on the gas slightly to accelerate more. I enlarged the Idle fuel restrictor jets from the stock .046" to .049" and totally cured the off idle stumble and made a world of difference in how it runs overall.
Good job diagnosing that problem.
@@holleycarbshowtosadvice40y90 Another thing I noticed is before it took about 1.5-1.75 turns from seated on the idle mixture screws to obtain a 13:1 idle AFR and after enlarging the IFR jets now the idle mix screws are at about 1 turn out from seated to obtain 13:1 idle afr.
Another great video
Thanks.
Thanks!
Great info
Thanks.
another informative vid.
Thanks
With respect to the transfer slot, most literature i've read say .020 , so thats exactly where i set my primary throttle blades on my Holley Street Avenger 770 carburetor, and with that, i set the idle at a healthy 800rpm on a ZZ4 crate engine, but i did have to close the secondary throttle plates completely to acheive that. Currently running with the unmodified main body, unmodified front and rear metering blocks and unmodified base throttle plate, IAB(.060), IFR(.033), PVCR(.060), antisyphoning(.028) and emulsion(.028). Its been known the SA line of carburators run leaner because its a street carburetor and not a performance one, but when i compared it to my spare, late 90s 3310-2 carburetor i have, front metering block only, all the orifices are exactly the same size(+/- .01) everwhere, unless its a later revised version of the SA770. If you are familiar, would you care to shed some light on that because i thought the orifices would provide totally different AF mixture ratios due to the design with different models, other than that, so far, so good, all i can do for now is read the plugs(mr43lts), gapped .040 , the porcelain stays white with a dark tan ring on the threaded portion, no AFR meter in use yet to properly tune the carb/engine, but thats next on my list. Thanks
Thats fine , you can set it at .010 if you want to. What this means is most of your idle mixture will be controlled through the idle mixture screws, now on a race car its different , it matters what your doing with the car racing or street driving.
There is so many ways of designing a fuel curve for instance holleys new ultra 750 dp, the high speed air bleeds are .036 and emulsion holes are .029, main jet size is76s. What I'm trying to explain is your jetting changed on this carb do to high speed air bleed and emulsion also the differences between venturi size and throttle plate size has a big influence on the type of curve you can run, if you run a small venturi and you increase your throttle plate size that carb will have to be jetted down because venturi air speed will increase. There is so many different fuel curves, also the ultra holley has a adjustable air bypass which is a nice feature. Hope this helps.
Good videos! Can you do some on the 0-9776 450 tunnel ram carbs? How to set them up Please
I don't have a 9776 right now, I'll try to dig one up.
very good video
Thank you
Hey Randy I wanted to ask you one more thing please & if you can give me your opinion & expertise on this. If I were to do the 750 main body mod to the 850 baseplate but use a 2 corner idle baseplate would I still have to do the modification on all 4 corners of the main body or just on the primary side? Let me know please & thanks. Also keep continuing to bring that knowledge to us we're just loving it man.
Tony just match the primary side and you should be fine if I'm understanding right , just make sure you do the idle circuit mod on the primary side.
Thanks for the CZcamss. I sent something that went to Matthew Cribb. Is that correct?
Yes thats correct. Thank you for the support
Hi Randy
Have you done a video on what changing the idle air bleeds do and also how the high speed air bleeds work ?
I have a 650DP on a 351C
The blades were already drilled and I’m just not as happy with it as I think I should be, I’m thinking it might be better without the butterfly’s being drilled.
Had a 750DP without holes and it ran beautifully but it’s much more responsive with the 650.
Would the drilled blades have anything to do with this ??
Best regards from Australia.
Great job on your content 👍🏽👍🏽👍🏽
Aaron drilling bypass holes is mainly for engines with high duration cams, where vacuum is lower than normal at idle, this bypasses air past the throttle plates which helps clean the idle mixture up, but I don't know if you have a hp cam. Give me your engine specs and explain what problems your having and I'll try to help.
@@holleycarbshowtosadvice40y90 Hi Randy.
My Clevo is 60 overbore.
Manual toploader 4spd
It’s a 214/224 @ 50
16 degrees of advance at idle
34 total.
It runs great but idles high.
Around 800/900 once fully warmed up.
Hello Randy i do have a question regarding boosters if you dont mind answering please.
What is the best booster for fuel economy tuning if i have a mild 351 clevland small port dual plane rpm preformer 2 600 cfm 1850 with no exsaught cross over and a 1.5 inch 4 hole spacer ? Thankyou
I believe the annular booster has the best signal, holley use to make a holley economiser carburetor just for good gas mileage, it had a unusual modified type of annular booster, looking at the top of the booster it was star shaped. They performed well and improved mileage. I believe Bolaws performance sells all kinds of annular boosters , look on there website. They may be listed as BLP or Bo laws performance, there in south florida . I'm not sure but I believe lots of small holes in a annular booster might be the trick. hope this helps. Also thank you for your contribution.
I have a proform 750.. on a hot 360 SBC...run rich at idle...idle mixture screws are out only 1/2 a turn ,any more then that car will stall from being way to rich...I believe I need bigger air bleeds.. am I correct.. transfer slots are about closed...put a bigger cam in it and now it's really rich....at idle....I mean really rich...any suggestions.?...70 front jet..81 back..
Dropped from 74 n 84 helped ..
6.5 power valve.....
May drop to 4.5 . PV..... maybe drop to 65 front jet n 75 back ..not sure if that's to small or ok....car is 3,400 lbs,,,runs 11:20 @118 MPH..1/4 Mile..488 gear,,on 31-18.5 x 15 tier....pro street car.78 Grand LeMans.... thanks for any help.....
Ok if your sure the transfer slots are right, next check for a leaking power valve, changing the power valve to a different opening or closing number will not help because the pv flows through the boosters and has no effect on the idle circuit ,unless the diaphragm is leaking then it will run extremely rich at idle. A blocked air bleed will make it run rich. Also make sure float level is correct. I would change the power valve first and then as a last resort try a bigger idle air bleed. Hope this helps.
Hey Randy, is it possible to use the Quick Fuel 650 dp metering block on a Brawler 600 dp , both are mechanical secondary carbs
Frank if you have pin gauges check pv restrictions and emulsion holes and idle circuit, change jets I believe they will be close enough. Hope this helps.
Question,it’s unrelated but what is the best way to refinish an old carb and parts that have no finish or is it needed without sending them to Holley?love your info
I can't answer that I don't refinish carbs.
@@holleycarbshowtosadvice40y90 ok it was early or late but I forgot to also ask with that question and I apologize for taking your time cause I meant to ask if it is indeed necessary?it is a 3310-1 and in great condition other than the coating only needing a final cleaning to complete.jegs screwed up a carb yrs ago and gave me a new one 3310 also but 4160 this is the original body 4150 am again I am sorry
Thats no problem , if I can help you just let me know. Take care
Hey randy , I have a question , my engine only runs if I’m dumping fuel with the throttle , won’t idle and stay running, engine is dual 1050 qft on a high rise tunnel ram , she fires off but won’t stay running .
William if it will stay running with you working the accelerator arm by hand then its lean, look for vacuum leak if nothing is found then check your idle circuit, open your mixture screws up counter clock wise, either out of adjustment or stopped up idle circuit or vacuum leak, most common causes. Hope this helps.
Awesome video! Quick question. This is my current setup on a 500 hp 383
650 speed demon, 22° initial and 36° total.
66 jets , 85 sec.
7.5" pv
ifr is 0.030"
pvcr is 0.067"
iab is 0.076"
Hsab is 0.0425"
squirters 37/35
It idles great, and the afr is perfect (cruise 13.9:1 and Wot is 13:1)
Only issue is that if I slowly slowly give it some throttle at around 2000 or so rpm, it slowly ramps to 16:1 afr, and then goes back to normal. If I get on the gas like normal, it'll be normal. When it leans out slightly like that, it almost sounds like it wants to lean stumble, but it doesn't stumble.
There's no load on the engine at that point, but what do you think?
It’s an issue with the wrong size power valve hg for the vacuum at part throttle.
You don’t specify, does this happen in gear or idle etc?
Manual trans: divide your idle vacuum by 2 to get a base PV hg.
Automatic subtract 2 from the engine vacuum at idle in gear to get a base PV hg.
*** Drive the vehicle and see if it smooths out the transition from the idle circuit to the main circuit. Adjust up or down 1hg from base to get perfect.
@@HeadFlowInc this is in gear driving at low 2000 rpms, with a manual tranny and 4.11 gears. I'm not talking about pv. I wouldn't even consider this as part throttle.
I have a 7.5" pv
I have 4.5" Vac at idle.
If I put in a 2.5" or a 3.5" pv like you just recommended, I would get way less fuel then if I were to leave the 7.5" pv.
I forget what Vac I have at around 2000 rpms, but I would say maybe 12" or 13". A 2.5" would never ever open with the slightest throttle input. So little throttle that I don't even think that the accelerater pump is pumping (I have it set right).
Original ifr was 0.033"
Would going from 0.030" to a 0.031" or 0.032" ifr, or maybe 0.076" iab to a 0.073" iab work?
I need a tad more fuel with a touch of throttle input. There is no load on the engine, so no matter what power valve I used (even blocked off) it shouldn't do that.
Jake its hard to run a engine with that much camshaft lean, you could try going to a .035 ifr or a 68 main jet or both , may have some luck changing to a annular style booster, I think you have done well to get to where your at with such a radical engine.
@@holleycarbshowtosadvice40y90 Yeah it is close now.... Running a 68 jet would then richen up my 3000 cruise. 3000 cruise is still a bit rich but ok at around 14:1 . I would like 15:1 but with my huge cam, it doesn't enjoy 15:1.
My throttle is opened so little at 3000 cruise, that I'm mostly on t-slot I think. That's why I'm reluctant to open up the ifr or close up the iab.
Since the iab is easy to change, I'll probably close it up to 0.073", and see what happens. Thanks
Jake you are doing a great job . Have a good day bud.
Is there a way I can contact you. I have a Holley HP series 750. Same mods have been done. And I'm idling fat at one turn out . But if I close it more I have that lean stumble. I have to get my gauge pins in there but it's a pretty sizeable restriction. I got this carb from a friend. Low speed cruise it breaks up alot . I assume I'm still pulling from the idle side .
E- mail me your number, Bigblockchevyman1121@gmail.com
@@holleycarbshowtosadvice40y90 I will reach out here in the next few days. Thank you.
Your welcome.
Hey randy I’ve tried adjusting mixture screws and restricting the idle fuel restrictor , my wide band still registers 12:8 at idle ,,, curious how you would approach this issue ?
Darrin try bigger idle air bleeds, don't restrict your idle circuit under .035 , the bigger idle air bleeds will let you pull more air. As you go up with the idle bleeds the mixture screws will come out further.
@@holleycarbshowtosadvice40y90 thank you , that makes perfect sense
The irf should be in the lower facory spot. The idle afr is more consistent under the fuel level. I have fixed more drive ability and idle problems on the newer carbs by moving the ifr down.
Moving the ifr will not cause any driveability concerns, I have changed a thousand of them,the only thing it effects is the restart of the engine at idle if the engine cools down it needs a little accelerator pump squirter to start and thats because there is unmetered fuel setting above the lower mounted ifr the best place is in the high position , the fuel is entering the ifr right in the air bleed steam which gives better emulsion of the fuel and air. Hope this helps.
If that were true, why did all the engineers at holley back in the 70's put them in the bottom. Submerged ifr goes all the way back to ww1 aircraft carburetors. It's in the naca 49 paper from 1919. Locating the Idle Jet below float level is more important than many people realize because cruising at a low RPM and steady speed the fuel delivery is nearly 100% through the idle circuit (T-slot), and, because intake vacuum oscillates rapidly over a wide range, with the jet above float level the AFR oscillates a lot, as much as 2 AFR or more. Smooth idle, clean sparkplugs and oil, and good fuel economy, all depend on a consistent idle-low speed circuit.With a high (above float level) idle jet, air can easily get upstream behind the jet when the idle fuel is pushed backwards by the pulsing. When the jet is submerged, the air cannot get back upstream of it as easily because the much greater viscosity of the liquid fuel (than air) on both sides of the jet impedes the backflow and the air cannot get back through the jet unless the flow is reversed for a longer period of time than the frequency of the pulsations.
Bud you can run it either way, but saying this has caused driveability concerns is wrong, it will have better air fuel emulsion at the top. Holley started putting all there nice performance carbs with high mount ifr years ago plus the ifr are changeable screw in and out restrictors . You have way over thought the idle fuel restrictor and it will work either way your choice. Hope this helps.
On my Holley 600 there is a jet centered on the bottom between ports. Why? What does it do..can I leave it out?
I'm sorry I don't understand your question , I need more information and exactly where this jet is located.
Maybe power valve blow out protection(?)
On bottom side of throttle plate centered between the four ports there is a jet in the channel that connects the four ports.
Randy, How do we contact you? I have a Mighty Demon 750 that is kicking my butt and I think you are not far from me. I'd like to have you go through it. I've been working on it but can't get it right. Need some new eyes on it.
Where are you located
@@holleycarbshowtosadvice40y90 Gainesville FL. My impression (which may be wrong is that you are in Jacksonville area.
Here my address 8909 garden street jax.fl. 32219
hi randy awsome vidio i have a problem with my 650 dp it will not idle with chock off please help thank u
Butch have you repaired the carb or has it set any length of time, is it a 2 corner or 4 corner idle circuit?
@@holleycarbshowtosadvice40y90 just put a kit in it , its the older holly 2 circute
Butch look at the throttle plate gasket, it is so easy to put the wrong gasket on and it will block the outer idle circuit passage. I feel sure that will fix it, but if you still have a idle problem let me know. Hope this helps.
@@holleycarbshowtosadvice40y90 thank u randy i will look at the gasket thanks again will let u know how it goes
I can’t agree on the upper IFR on a street car with a reasonable street cam. A smaller IFR lower position will flow more consistently below fuel level, it’s pure science. Most todays (quick fuel) are upper. Changing to lower IFR allows for smaller hole and eliminates the dead rich black spark plugs. Again street car mild reasonable build.
I'll have to agree to disagree. But either way will work. Have a good one.
Is the actual IFR the brass incert size or is there a hole underneath the brass insert ??
I have 2 carburetors one is a 600 that has the incerts at the bottom and 1 is for a 670 that has them on top looking down in the holes of IFR i can"tsee any small hole underneath .
I have a micro drill bit set from size #50 to 70 #66 is .035. The brass hole is in the 50"s
Most holleys have a brass insert on each side of power valve, a small cutout that has two holes. One is to the main well and the other usually has a brass insert feeding the idle circuit that is the ifr, now if there is no brass insert , than look at the top left or right of metering block and there should be a screw in replaceable idle fuel restrictor. Usually .035 is close. There are some 600 cfm that have idle tubes inside the metering block that is all most lmpossible to take out without damaging the tube or the block itself , in this case i find some metering blocks that have the brass inserts. Hope this helps.
@@holleycarbshowtosadvice40y90 Thanks for the reply on my 600 block I see the IFR at the bottom one brass incert is missing but the hole inside the brass is way bigger than 0.35 it"s probably in the 40-45 size. The sweet spot on my AFR is 12:50 in drive if I try to go to 13:00 or above it acts up and idle quality is trash I'm using full manifold vacuum if I used ported I can go way leaner on the idle circuit but I guess that's why they started to use ported . As far as tuning for highest vacuum I start out at 1.5 turns out and I end up turning the right side in for higher vacuum but the left side wants out ? For higher vacuum I'm thinking of buying the pro form standard purple block so at least I can try different sizes . Funny thing about the 670 SA block it won't run at a idle it was super Rich in the 10 on my AFR gauge I jetted it down only 64 is the Lowest jet I had made no difference it would run on the accelerator pump but once let off it would be super Rich and not want to run at all at 1.5 turns out that 670 block has no emulsion holes at all a on the well like the other blocks do and small holes up top the IFR are on the bottom and smaller than the 600 size .
I don't know if I'm missing something but I understand about 0.31 0.33 0.35 etc in example of the pump squirter size holes .
I have a micro drill bit set #61 to# 80 # 64 is 0.35 putting that in the IFR hole i can move it side to side ? Not sure why other carbs need to be drilled out and the ones I have are bigger than the average 🐻 bear .
Unless we're talking 650 and up have smaller IFR ?
Thanks!
So did you acquire the sliced orange looking booster carb or choose annular?
@@broke_dongle left it like it was bud