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Discussion Starter · #1 · (Edited)
hello all.
struggling with a lean condition off idle. WAs going to bump this thread but the page suggested starting a new post because of its age.


i am running the idles screws out ~4 turns and increased the pump nozzle to a 35. and still stumble a little.

Anyway,, looking at the idle air bleed spec's it is supposed to be 70/39 out of the box. I have 78/63, The main bleeds are 31s

I called to QF/Holley. as always, they never answer the phone. Anyone else have this mismatch? I am not a professional tuner so i don't really know what it should have but it seems big/lean
 

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Discussion Starter · #2 ·
Also the main Jets are 66 and not 68 as spec'd

 

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Yeah, idle air bleed sizes are very lean, especially the secondary side.
Matches up with the fact you've got to have the idle mixture screws cranked way out trying to get it rich enough.

The main jet size won't matter for the idle circuit problem.
2 jet sizes smaller is a standard tuning jump for testing, so it's fine for right now until you get to WOT testing .

I would leave the idle fuel restrictions as-is, change the air bleeds to what the spec sheet says they should be, put the pump shooter back to stock #31, and give it another test.
 

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I can tell you right now its a quality control issue as I had bought a few of the quick fuel slayer 600 carburetors last year and I had to buy a set of air bleed blanks and drill them to stock size in order to correct what Holley messed up. The problem is the slayer main bodies are the same main bodies used on the Quick Fuel Hot Rod series carbs and also on there Brawler etc and the main body is originally setup for a four corner idle on the other carbs that are the more expensive ones and with either downleg or straight leg boosters and I am figuring in the process of things at times they are just rushed out the door and there not catching the part where its being made for the Slayer series carb which are setup as a two corner idle when you get it out of the box and in the process its being missed and there putting the wrong secondary side idle air bleeds and at times the wrong main air bleeds.

I had one where it had the squared idle air bleeds of .070 front and back on one of my 600 Brawer carbs that has side hung bowls it is also setup as a two corner idle out of the box and the idle air bleeds had to be changed. I then had a good deal on a Quick fuel slayer 600 which has the center hung bowls and the secondary idle air bleeds were .063 and all four main bleeds were .063. Talk about being way off. If the average person who does not know these functions and areas on a carb and to look things over and not know what to find ends up being in the situation your in. The carbs I got were brand new and not returns. I had to buy a few ten packs of air bleed blanks and drill them to size and put them on the carb. But the good thing is they are screw in bleeds and easily fixed.

I have worked on Holley style carbs for a long time and learned the trade of learning to customize carbs that don't have the screw in bleeds to be able to have that option using drill bits and brass allen cup screws and because of a long and drawn out history of receiving Holley carbs that I had to fix because of quality control issues.

I had also bought a few of the Holley brand 600 main bodies of the vacuum secondary and 650 double pumpers and the pressed in air bleeds were always checked for size and stuff but they did a poor job of putting in the boosters and they could be wiggled with my fingers with no effort and I ended up buying a kit from a carb company that allows me to put in screw in boosters to correct and fix them. I had a 670 street avenger main body I used as well from last year and it was the same thing, loose boosters and I did not want to have to fix another one and sent it back to Holley and they looked at it and said they would just send me a new one.

New one came and same problem. I did not even bother this time and its on my list to fix. Holley still had good stuff don't get me wrong but they are like everybody else, more quantity then quality out the door. Buy some air bleeds of a smaller size say .028 as a starting point and it will be easier to drill since they already have a hole drilled in them versus ones that are solid blanks as it will take longer to drill them out. Usually on the 600 slayer it will have .039 on average like you posted above but they have made slight changes on the calibration over the years since Holley bought Quick Fuel out. Same thing on the jets.
 

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New doesn’t mean correct. Always tear it down and see what you really have. Also note the online specs could be listed wrong. Trust nothing, verify everything.
 

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And its been a while but I think the primary idle feed restrictor in the metering block should be around .033 but might be .031 as I have seen it vary and the secondary metering plate is unable to be changed and it has been in the past .039 just for reference. Depending on what your engine specs is and camshaft specs etc you might have to lean it out some if its not very radical or if it is a bigger cam say in the [email protected] or over it might be pretty close or might need more. Just make sure before you ever venture into that area of tuning that you educate yourself on what and how they function and I recommend the book below as it will give you all the ins and outs on tuning a Holley style carburetor and helping you with a lot of advanced knowledge on tuning and changing things that the average tuner never seems to learn.


For me on the Quick fuel slayer carb I always remove the metering plate and get a cheap 600 Holley vacuum secondary metering block so like that I can modify it for changeable secondary idle feed restroctors using brass allen cup screws so I can tune it and most of the time lean it out on the idle circuit since my engine does not need such a rich setting on the secondary side and 4150 which means a secondary metering block is on the Holley carb, has more options for fuel rail hookups versus a 4160.

The secondary metering plate can be drilled and tapped for using 6-32 brass allen cup screws as before Holley bought out Quick fuel they used to have that option on them but as always Holley cheapened them out as much as possible and took that feature out. The problem is the angle on doing it. Much easier with a metering block. Not saying you have to run out and get a secondary metering block as if you buy a billet set then its already made for that. I just go to a site called allcarbs.com and they have a secondary metering block conversion kit that has the same metering block used on Holley 670 street avengers and also 650 vacuum secondary Holley brand carbs. Its like $43 for the block and way cheaper then going billet.

Anytime I get a carb regardless if its used or new I always tear it down and measure everything and even check for any warped spots as well. Long story there.

 

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Discussion Starter · #8 ·
Summit has shipped the correct bleeds but they have to come from TX so it will be next week before i see them.

I should just send it all back and wait for an 650 AED to arrive. I only went 4160 for simplicity of install and this motor does not need a DP.

I would go EFI but knowing my success rate with aftermarket parts I will be the guy how gets a dud and spend months screwing with only to toss it out.

Chris
 

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When it comes to duds I am a king when it comes to receiving bad parts. I have had so much bad luck over the last 13 years in general since I learned more about stuff and got into things really hard to fill my brain and carb stuff has been an ongoing thing with me. I have bought some extras and sold some others that I have been through and all I can say is back in late 98 I had a bad run with Holley and went to an Edelbrock carb for about ten years until I decided to go Holley again and learned over time you just receive bad parts here and there.

The thing is beyond Holley and ever since in my understanding since I started to see signs of things at around the year 2000 it seems the days of decent quality control was replaced with quantity first then quality later and has only gotten worse especially since a lot of stuff has went to China and a lot of ups and downs with many aftermarket stuff and many brands that were once separate are now all bought out and owned by one company and the days of many different brands to choose from are pretty much becoming extinct like the dinosaur.

I would not give up on your quick fuel carb as compared to the Holley brand ones they are still better quality and offer more tuning features if they still have them available in the metering blocks besides the air bleeds being changeable. I myself will stick with carb as long as I can get parts for them versus EFI.

I like the simplicity of tuning a carb vs EFI and having to setup all that stuff which I don't doubt I can do its just a hassle for replacing the entire fuel system and if something goes bad on the unit itself then your toast until you can get Holley to fix it and if out of warranty period then your not going to be able to go to a local store and get what you need for a simple fix. That is why I won't convert yet. With the way the world is changing and wanting to go electric, ten years from now we might have nothing for hot rods not even aftermarket parts being available as they seem to want to kill all of it.
 

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Discussion Starter · #10 ·
When it comes to duds I am a king when it comes to receiving bad parts. I have had so much bad luck over the last 13 years in general since I learned more about stuff and got into things really hard to fill my brain and carb stuff has been an ongoing thing with me. I have bought some extras and sold some others that I have been through and all I can say is back in late 98 I had a bad run with Holley and went to an Edelbrock carb for about ten years until I decided to go Holley again and learned over time you just receive bad parts here and there.

The thing is beyond Holley and ever since in my understanding since I started to see signs of things at around the year 2000 it seems the days of decent quality control was replaced with quantity first then quality later and has only gotten worse especially since a lot of stuff has went to China and a lot of ups and downs with many aftermarket stuff and many brands that were once separate are now all bought out and owned by one company and the days of many different brands to choose from are pretty much becoming extinct like the dinosaur.

I would not give up on your quick fuel carb as compared to the Holley brand ones they are still better quality and offer more tuning features if they still have them available in the metering blocks besides the air bleeds being changeable. I myself will stick with carb as long as I can get parts for them versus EFI.

I like the simplicity of tuning a carb vs EFI and having to setup all that stuff which I don't doubt I can do its just a hassle for replacing the entire fuel system and if something goes bad on the unit itself then your toast until you can get Holley to fix it and if out of warranty period then your not going to be able to go to a local store and get what you need for a simple fix. That is why I won't convert yet. With the way the world is changing and wanting to go electric, ten years from now we might have nothing for hot rods not even aftermarket parts being available as they seem to want to kill all of it.
Agree, I want to go EFI on my CJ7 but if I am 500 miles from home, In Moab, Rubicon etc the last person i want to depend on is holley tech support. At least with GM TBI there is a Napa auto parts or a easy donor at the junk yard.
 

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Discussion Starter · #11 ·
follow up,,

So i pulled a 600 vac sec holley off my AMC and stuck it on the ford 400. 31 nozzle, 68 jets. The motors idles perfect at 800 in neutral and maybe 750 in gear. flawless,,, zero changes made. no hesitation.

Summit sent me the correct bleeds and jets for the QF. Put it back together with the 31 nozzle, stuck it on the AMC andddddd it will not idle under 1200 RPMs. Idle screw not making contact, high idle cam not engaged, timing unchanged, mixtures screws 1.25 out and AFR at ~13. No vac leaks, fresh gasket at the intake to carb. Pulled and plugged the PCV line just to make sure it wasn't causing the high idle. (the AMC ran flawlessly with the holley)

Summary, Both motors are 11+-1 with aluminum heads. AMC is a 527/[email protected] the ford is .570/[email protected] Nothing radical. Both motors run nice with the bone stock holley and both run like ass with the QF.

I have 10 days left to send it back before the 90 day refund period is up.

What am I over looking?

Chris
 

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Does it run well at cruise and WOT with the new bleed combination? And just idle too fast?

High idle speed is air getting in somehow.

With the carb off, have you visually verified the primary throttle blades will close tight in their bores when the speed screw is turned out off the stop??
Make note of the rear throttle shaft setting for future reference.
Both shafts should be capable of being shut tight with their stops removed.

Have you tried closing down the secondary throttle blades some??
 

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I have had a problem like that before with using the electric choke on the quick fuel carb and if your fast idle screw is set up to high on the high idle when the choke is engaged and then it lets off the fast idle cam after you hit the gas pedal and it lets off and idles down, sometimes the fast idle screw even though the fast idle cam is no longer on the highest ramp and the choke has open all the way you have to look underneath the carb as sometimes the fast idle screw will be making just a slight contact with the fast idle cam still on the lowest part of the cam even though its not supposed to.

Basically you don't want the fast idle setting to be to high with the fast idle screw engaging the fast idle cam when the choke is engaged as when you let it off the screw can sometimes still make a very faint contact on the fast idle cam and thus making it not able to close the throttle plates all the way. Basically you only have a certain range you can set your fast idle as if its to high then this will happen. Same goes with an electric choke on a holley as well. I discovered this myself and took me days as I could not find any vacuum leaks or any other issues and could not get my idle back down enough. I finally found by shining a flashlight and looking down on the bottom of the carb and with holding my primary throttle shaft close and making sure the fast idle cam was not engaged and the choke plate open I could see the screw just barely touching the fast idle cam.

So I just screwed it out just enough to not catch it when its off and then when my fast idle came on it would be just a hair lower on the high idle setting but it was enough to allow the choke to do its job. That is something to check.
 

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Discussion Starter · #14 ·
Figured it out last night,, I checked the transition slot before installing but paid not attention to the secondaries. Pulled the carb back off (could not find a short/fine enough screw driver) and turn the secondary idle screw out ~one turn. Idles nice, crisp throttle, have not test drove.

Maybe the guy that assembled this carb was just having a bad day. Hopefully it will perform now. I need another 600 for a SBF and the TF does offer a lot for the base price.

Chris
 

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One thing I did to simplify changing the secondary idle adjustment screw was to replace the original screw with a small thumb screw. This allows setting it without removing the carb. Even with the engine running.
The thread you quoted in your original post was mine. I have learned a lot about the QFT carbs in the 6-1/2 years since then with the help of the guys on this forum.
 

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Discussion Starter · #16 ·
One thing I did to simplify changing the secondary idle adjustment screw was to replace the original screw with a small thumb screw. This allows setting it without removing the carb. Even with the engine running.
The thread you quoted in your original post was mine. I have learned a lot about the QFT carbs in the 6-1/2 years since then with the help of the guys on this forum.
Hello,
Sometimes I think Post to much but your old thread is a good example of helping others even if it is years down the road. If not for you post i might not have looked at the bleeds as soon as i did.

What is really sad is your post is from 2015, almost 6 years ago and TF still has randon bleeds/jets being installed in carbs. I wonder how many people dealing with an issue just learned to accept it.
 

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Just imagine how far the human race has come since the 1960’s when my unit’s CO, a mustang colonel from WW-II felt the young generation didn’t give a rats about what they were doing.

It would appear that things haven’t improved.

Bogie
 

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Discussion Starter · #18 ·
Still need help.
Test drove today and still have issues.
It needs ~12-1 AFR to idle well and not stall in gear. (good enough)
Has off idle stutter with the 31 nozzle, 31 nozzle was perfect with the holley,
Light cruise (35mpg like in a neighborhood) it will peg the AFR gauge to 18 and it sound like dodge with MDS.
if i light accelerate it will run at 13.5-14 AFR. (good enough)
WOT 14 AFR to ~5000 rpm. It does pull hard.
Under all conditions, except WOT and idle the AFR is bouncing around 2 points. It never did that before, the gauge is an autometer.

So where do i start? I think going from 68s to 70s will help the WOT and maybe the light cruise. I got as much as 15mpg with the old holley and cruise is ~14-1 AFR.
Does anyone know what orifice the OE holley 600 had for air bleeds.

Sorry to ask so many dumb questions but this is a simple mild motor and in my mind the QF should not be so temperamental out of the box. I have 9 days to return this thing and start fresh.

One other difference is this carb is the black coated. Never had one before, could the costing possible get in a circuit somewhere and cause this 2 point swing in my afr.

chris
 

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The stock Holley 600 vacuum secondary in the last ten years on the model 1850 manual choke and the 80457 electric choke carbs come with .078 primary idle air bleeds and .048 secondary idle air bleeds and the primary jets are 65 or 66 but most of the time it has been 65 primary jets and the primary metering block has a .028 idle feed restrictors and the emulsion ports are .028. Comes with stock 6.5 power valve with a .046 power valve channel restrictor size. Vacuum pod comes with a silver spring. The same specs are for the older 2 corner idle Holley 670 street avenger as well but it has a secondary metering block which comes with .028 emulsion ports and a .031 idle feed restrictor size and 68 rear jets which has the same way to lean of a setup out of box.

On the main bleeds they are .025 front and back and sometimes have been .028 but mostly .025. The secondary metering plate has .031 idle feed restrictor size and is equal to about a 65 or 66 jet which is way to dang small on the secondary side of things and on anything out side of a bone stock smogger engine it makes for to lean of a wide open throttle. Since they changed the Street avengers of the aluminum ones they are a four corner idle now it differs only on a few things. The secondary idle air bleeds should be the same as the primary at .078 and the rear metering block would have a .028 ifr size like the front. In case anyone will come across this post someday.

I have worked on them so much and customized and spruced them up and improved on them over the years I just know all the specs right off without even looking it up.
 

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Also I just recently read and put these notes down on my tuning stuff when a person was tuning a Holley style carburetor and I can't remember if Holley or Quick fuel but I read that on the main air bleeds if they are on the smaller side say for example .025 on a 600 or 650 cfm carburetor the smaller sized main air bleed will start the flow of fuel on the boosters later on in the fuel curve and will extend further in the higher up rpm range. The main air bleeds being on the bigger size say at .031 would cause the boosters to come in earlier but will taper off earlier in the higher rpm range and not extend as far compared to the smaller size.

I can't say that is completely correct but I read from somebody using a wide band gauge to tune with and some other tuners had quoted this information as the person was trying to get there wide open throttle air fuel ratio to be the best they could be and had issues and jetting was not getting the full effect and tune they was looking for. Basically smaller sized bleeds will bring on the fuel later but help extend the richer air fuel mixture later across the entire fuel curve higher up and extend further in the higher rpm range vs bigger sized main air bleeds which won't go up as far it comes in sooner and will not extend up as high. But I am sure there a a lot of variables there with jetting changes along with power valve channel restrictor size playing a factor in things as well as the size of the carburetor and also the engine specs and type of intake manifold and camshaft etc.
 
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