Fix That Rich Quick Fuel

[wbulk]

History
I am an older guy. Been working on carbs since high school in the 60s. I started tuning for altitude when I moved to Utah 35 or so years ago. I really got into detailed tuning about eight years ago when wide band gauges became reasonably priced and a friend who was Kirkham's foreman, showed me how Kirkham tuned carbs. I have tuned many Holley's, Quick Fuels and Edelbrock's since.

I have to say that I believe Quick Fuel is a great carb for the money if you have any of these few fixable problems take care of them. The adjustability is what you really need to do a good job of tuning, especially for higher altitude.

The Problems
1. Three of the last four Quick Fuel's I have worked on over the last two years did not have the small spring in the anti backfire valve that holds the check ball up. Without a spring the check ball falls down and can close off the vacuum passage. Vacuum keeps the power valve closed except when that engine vacuum falls below the PV setting. When it opens it dumps fuel through the PV restrictors into the main well, richening the main metering circuit. This symptom is the same as a bad power valve. It will make the engine run really rich when you may not want it to.
So, this is how it works. When the engine starts, vacuum pulls the ball down against the spring, opening the passage so the PV can close. The PV stays closed until the vacuum drops below the vacuum rating on the PV or the engine stops. Look at the metering block with the PV installed. The diaphragm side sets in a chamber in the main block. If that chamber cannot get and maintain vacuum the PV will open by the spring force in the valve. You can order a repair kit from Holley that comes with the correct size drill, ball and spring. You need a drill press to be safe.

Sometimes the problem can be an old hard gasket between the metering block and the main block that leaks air and cannot maintain vacuum. I have also found a poorly machined surface on the main block surface where the metering block mounts. I am now working on a Quick Fuel 830 SS that had that problem. This main block has QF and Proform cast into it. Most of the time you can fix it with a straight wide flat file. You can test the fix by installing the metering block and float bowl with a good gasket and tightening the four screws. With the throttle plate off apply vacuum with a Mity Vac to the small hole to the power valve chamber in the bottom main block. This will test everything upstream and should maintain reasonable vacuum.

2. Quick Fuel used or maybe still uses an unusual throttle plate. I do not know if it has been changed as of this posting. On a 4150 style carb that has front and rear metering blocks with four corning idling the problem may be with the rear throttle plate body. In each secondary bore it has two idle passages. One standard screw passage for a normal 4150 four corner adjustment carb and a drilled idle passage below the idle transfer slot that would normally be for a 4160 style carb without a rear metering block, or a 4150 with the two front idle system only. The problem is with 4150 style with four corner idle screws. With this carb you have the two idle ports per bore that are active creating a conflict. You have that drilled idle port below the transfer slot and the idle screw port, both delivering idle fuel to the back barrels. So, when trying to adjust the rear idle screws you can get lost and not be able to adjust the rear idle circuits. You have fuel coming in the drilled hole below the transfer slot and fuel coming in the idle screw port at the same time. Not know this you cannot figure out why they won't adjust.

I tried three times to get Holley tech support who owns QF to explain how they wanted this to work without an answer until last month (7/23), when a tech was able to find the engineering drawings and told me he saw the 4150 four corner carb was supposed to have a plug in the drilled port below the idle transfer slot. This would eliminate the conflict and allow for normal adjustment with the idle screw.
About a year and half earlier I had done this on my own carb by filling the hole with JB Weld which worked really well. I did a QF 750 SS this week with great results. Everything adjusted like it was supposed to. Every QF I have worked on I have not seen that passage plugged.
If plugging that hole with JB Weld spray the hole out really well with carb or brake cleaner first. I then use a small glue syringe called Crystal FX that I get at Hobby Lobby. I file the metal needle tip to the angle I need to seal the hole and fill just the plastic chamber that holds the needle with JB weld. Do not put the JB weld in the upper tube where liquid would normally go. The JB weld is too thick. Press the JB Weld in slowly until you see it come out the idle transfer chamber looking from the top side of the throttle body. Stop when you see it just coming into the transfer chamber. Do not overdo it and make sure you do not leave JB Weld debris in the transfer slot. I use a magnifying headset to see what I am doing.

Pictures added over on Club Coba. I can't add pictures here. http://www.clubcobra.com/forums/holley-tuning/147135-fix-rich-running-quick-fuel.html

Good Luck
Wayne

[GoDadGo]

Wayne,

Thanks for creating this post because many of our forum members are Holley Style Carburetors.
As for me, I stink at tuning those units so I am running an Edelbrock AVS 800.
I'm sure your insight and experience will help a lot of folks!

Steve

[Jim1855]

Wayne,

Just a question. Are the QuickFuel carbs the only ones that have the extra idle circuit hole? Is Holley doing the same thing in their Holley brand carbs?
I've never seen the additional hole in my ProSystems 4150s, doesn't mean it's not there.
I've yet to own a carb with the anti-backfire circuit but I'm sure any or most new carbs will have this.

Thanks for the write-up. I keep learning about carbs, every bit helps.

Jim

[wbulk]

Jim.
I have a Holley on my Cobra now and do not have this issue with the rear idle circuit or the anti backfire valve. In fact the repair kit is a Holley part. However, the issue with the main block metering gasket and the surface being uneven do apply to Holley's when they get older. The surface can warp.

[wbulk]

Steve,
I do like Edelbrocks and have a couple of them. They are slightly down on top end HP but they are really good street carbs and are stable. Stable, meaning they hold a tune and the idle usually holds constant from one drive to another. They also seem to have less problems with the accelerator pump circuit. When I tune those the power enrichment is usually richer that I have to adjust. Same thing with the PV restrictors on the Quick Fuels that serve the same function.

Edelbrocks do not have an anti backfire valve as they don't need one. The power enrichment is accomplished by the step in the needles with the jets. Springs control when the system comes in.

[SJDave]

Read the post a while ago but finally had time to pull my Quickfuel SS750 off to see if I have the problems you noted. Yes, both of them, no Spring in the ball check valve for backfires to the Power Valve and two extra fuel passages in the Secondaries below the Transfer slot.

I just ordered the spring kit today so it will be a week before I can report if things have improved with a leaner idle condition.

Here's some pictures of the problem areas for those that want to go look at theirs if they have a rich idle. I used a Harbor Freight punch i bought a while ago in a set to tap the ball and keeper ring out of the carb base. Came out easily with light tapping. On the extra idle fuel channels that should have been plugged in the secondaries, I used some .023 stainless welding wire and wicked some super glue in around them used a piece of welding wire to carry a small drop.

Thank You Wayne!!189630189631189632189633

[chmhasy]

Don't know if this is too much, but would it be possible the next time you fix a QF. Can you film it and throw it up on Youtube.
As I have a QF HR-580-VS and I don't even know what a PV settings is.

Thanks

[SJDave]

Don't know if this is too much, but would it be possible the next time you fix a QF. Can you film it and throw it up on Youtube.
As I have a QF HR-580-VS and I don't even know what a PV settings is.

Thanks

Seems like I'm always rushing to fix stuff and never have time to do videos, but if I do it again I will try to make a short one of the critical steps.

I tried to ATTACH a really good description of how these carbs work that I have read over and over, it was just some guy on a forum in 2010 who was very knowledgeable and took the time to write something up. It is way better then anything on the Holley website in Tech support videos or written documents. I guess with most folks going to EFi these days, there is little interest on their part in doing more informative carburetor help articles....pretty slim picking on their website. ** It is too big a PDF to attach...stupid. PM me your (or anyone else) Email address and I will send to you along with many other articles I have about tuning.

Your carb is all diecast aluminum, versus the billet aluminum base plate and metering blocks on the SS750. The SS750 also has dual accelerator pumps where your carb only has the one on the Primary side. But otherwise it's in the same family of carburetors. So it has a Power Valve (PV) on the Primary side just like mine, and an anti backfire check ball in the base plate just like mine. Is yours missing the spring too?? No idea. As far as the extra fuel channels in the Secondary side that are supposed to be "plugged" with a 4 corner idle screw setup (Mine and yours both have this; four idle adjust screws), could be the die cast ones don't have the extra hole but I do not know for a fact. Unfortunately you have to remove the Carb to look under the throttle plate to see if there is a small hole below the transfer slot. Use some fine wire (.023 " max) to see if it is plugged or it is open to the bottom of the base plate.

If your idle is not pig rich, you are probably OK and don't need to mess with it. That is the only reason I picked up on this post...been trying to figure it out for 7 years now. You would think Quickfuel (before they got bought) or Holley would put out a Technical Service bulletin to registered buyers of their products and send you a "kit" to fix it, or do an exchange. ARRRGGGHHH!

[SJDave]

Just wanted to let folks know that Holley Tech Support has no idea this was going on and are unwilling to do anything to help rectify the situation unless it is less then 3 months since you purchased the Carburetor. They told me I can buy the anti backfire kit for $15.95 to get a spring. Well it's more like $30 after shipping and handling, just to get a $1 spring.

They deny they ever shipped a carb with extra holes in the secondaries that were not plugged. Looks like that rules out the Holley Sniper FI kit for me down the road!!

[Avalanche325]

Some Holley engineers split off and formed QF because Holley wouldn't bother making better carbs. QF was making great carbs. Then Holley bought QF. That is pretty much a tragedy. Now we have the QF name and the old Holley quality.

[cv2065]

Just wanted to let folks know that Holley Tech Support has no idea this was going on and are unwilling to do anything to help rectify the situation unless it is less then 3 months since you purchased the Carburetor. They told me I can buy the anti backfire kit for $15.95 to get a spring. Well it's more like $30 after shipping and handling, just to get a $1 spring.

They deny they ever shipped a carb with extra holes in the secondaries that were not plugged. Looks like that rules out the Holley Sniper FI kit for me down the road!!

Thanks Wayne and Dave. I love QF carbs, and the 750SS I swapped onto my BP 427 in 2019 was always crisp on the throttle, but seemed like I smelled of fuel too much and was running a bit rich regardless of tune. Perhaps this was the issue? Are we saying that Holley 'quietly' fixed the issue and all new QF carbs going out the door as of 3 months ago have been addressed?

[SJDave]

Got to drive my car 30 miles to a Cobra Breakfast with the local guys and WOW. All the cold start idle issues are gone now, the garage doesn't stink, the choke actually works now, it idles beautifully and feels like I gained at least 50 HP!! If you have any Quickfuel Carb with 4 corner idle, do yourself a favor and check for the extra "unplugged" fuel feed holes in the secondary's and for the "spring" in the anti-backfire setup.

Thank You Wayne again!!

[chmhasy]

So I found some information on the Holley website for this issue. Looks like one is for the QFT by the P/N not sure it they are interchangeable.

Drill with 2 balls 2 springs and retainers P/N 125-500 https://www.holley.com/products/fuel_systems/carburetors/carburetor_tools/parts/125-500
https://documents.holley.com/199r9898-2.pdf

Drill with 1 ball and spring and retainer P/N 25-100QFT https://www.holley.com/products/fuel_systems/carburetors/carburetor_tools/parts/25-100QFT
https://documents.holley.com/99-18__25-100_blow_out_protection_kit.pdf

[wbulk]

I need to do a YouTube video. It's is pretty simple to do the fixes. Think of how many Quick Fuel and Brawlers are out there with this problem.

[wbulk]

The rest of the Story
About three or four years ago I bought a new QF 600CFM Slayer which is a 4160 style carb, meaning it had a metering plate on the rear instead of a metering block. It had the anti backfire valve problem with the missing spring. That caused me a few tanks of gas to find that issue and Quick Fuel sent me the repair kit to fix the problem.

Saving Money
When I had the throttle plate off I realized it was drilled for the idle screw passages of a 4150 carb. So then the light came on in my head. I realized if I bought a metering block from a 600HR series carb with the longer screws, idle screws, air bleeds, idle restrictors and the right jets I could easily turn the Slayer 4160 into a HR 4150 four corner idle carb with better metering. The big plus was that after the conversion it was about $100 cheaper at that time than just buying the 4150 HR carb. It was a win, win, win. It was at that time that I found the conflict with the idle ports below the idle transfer slots, that was correct for a 4160 carb and the idle screw ports of the 4150 metering block that I just put on. I realized the solution was to block off that idle port below the transfer slot. This was indeed a universal throttle plate that could be used for either style carb as long as you blocked off the holes below the idle transfer slots when using it for a 4150. It could be that Quick Fuel contracts for the manufacture of these throttle plates and during the assembly process it was missed, if used on the 4150 those holes needed to be plugged. This was just as the Holley tech guy I talked to a few months back found on the engineering drawings. I have since called Holley again and told them of the problem and that they really needed to put out a bulletin on their site to explain the situation. Since that first carb every Quick Fuel and Brawley 4150 carb I have worked on has had the idle passage conflict and the power valve was correct and working on one newer Brawler I still have.

One finale note. For every Quick fuel I have worked on if the retaining plug for the anti backfire valve was brass it was missing the spring inside. When you drive that plug out it looks different than the Holley steel silver plug. I am wondering if Quick Fuel before Holley bought them thought this design would work without a spring, who knows.

This this is a great carb with these easy fixes. Don't suffer, just fix it.

Wayne

[wbulk]

CV2065, I have no idea.

[BUDFIVE]

I just bought a new QFT Brawler br-67318 650cfm 4150 style with four corner idle screws 8/7/23 from Summit. From the above thread it seems likely I have the secondary idle mixture conflict and perhaps the missing power valve check ball spring. Did I read this correctly?

I read positive reviews on the brawler out of box install and running ease but I wonder if I should mess with it or return it since it’s only been in my shop, unused, for a month. Thoughts?

It’s been 30+ years since my Holley tuning days and those were 4160 I think (#1850 600cfm, #3310 750cfm, both vac sec) so I’ll be ramping up on this carb on the 347 I’m building for a roadster (kit due November). I will be tuning with an AEM WB O2 sensor and gauge. I would love the data you mentioned SJDave and I sent a PM with contact info.

I’m trying to decide if I should make these mods before starting my new engine. If it’s too rich at idle, what would the impact be if I closed (screwed in) the secondary mixture screws and opened up the primary screws? Would the secondary idle fuel be reduced enough to make the primary idle circuit dominant?

Thanks for starting the thread wbulk, I sent a PM with my contact to you as well.

BUDFIVE

[SJDave]

So I found some information on the Holley website for this issue. Looks like one is for the QFT by the P/N not sure it they are interchangeable.

Drill with 2 balls 2 springs and retainers P/N 125-500 https://www.holley.com/products/fuel_systems/carburetors/carburetor_tools/parts/125-500
https://documents.holley.com/199r9898-2.pdf

Drill with 1 ball and spring and retainer P/N 25-100QFT https://www.holley.com/products/fuel_systems/carburetors/carburetor_tools/parts/25-100QFT
https://documents.holley.com/99-18__25-100_blow_out_protection_kit.pdf

My understanding is both these kits are to "ADD" the anti backfire feature to protect the Power Valve in Carbs that did not have them. I purchased the 25-100QFT which was the correct kit for my Quickfuel SS750. The Ball is identical diameter to one that came in my carb, the spring fits but a little tight on the bottom turn, had to use an exacto blade to seat it all the way down in the hole. The plug doesn't fit my carb at all, I would have to drill it out larger with the supplied drill bit. I reused the old plug.

[SJDave]

I just bought a new QFT Brawler br-67318 650cfm 4150 style with four corner idle screws 8/7/23 from Summit. From the above thread it seems likely I have the secondary idle mixture conflict and perhaps the missing power valve check ball spring. Did I read this correctly?

I read positive reviews on the brawler out of box install and running ease but I wonder if I should mess with it or return it since it’s only been in my shop, unused, for a month. Thoughts?

It’s been 30+ years since my Holley tuning days and those were 4160 I think (#1850 600cfm, #3310 750cfm, both vac sec) so I’ll be ramping up on this carb on the 347 I’m building for a roadster (kit due November). I will be tuning with an AEM WB O2 sensor and gauge. I would love the data you mentioned SJDave and I sent a PM with contact info.

I’m trying to decide if I should make these mods before starting my new engine. If it’s too rich at idle, what would the impact be if I closed (screwed in) the secondary mixture screws and opened up the primary screws? Would the secondary idle fuel be reduced enough to make the primary idle circuit dominant?

Thanks for starting the thread wbulk, I sent a PM with my contact to you as well.

BUDFIVE


I actually found Wayne's post because I was looking for tips on how to tune the same CARB that you have, for a close friend on his '33 Hot Rod. He purchased his from Summit about 3 years ago (I bought my SS750 7 years ago) and it DID NOT have the extra fuel holes in the secondary and WAS NOT missing the spring in the anti backfire circuit.

It's simple to check, just use the photos I posted earlier for location of the extra holes and the check valve. You can see the Ball sitting on top the helical spring from the bottom of the carburetor, the ball should be spring loaded UP. When I shook my carb up and down, I could hear the ball...you shouldn't if the spring is loading it. You can also take a small diameter rod or drill and try to push the ball up while holding the Carb above your head. If it doesn't move, the spring is in there. If it moves, no spring. Then you have to remove the plug on the other side of the throttle plate to remove the ball and install a spring. That's where i used the HF punch against the ball from the bottom to drive the plug out.

[BUDFIVE]

Thanks, I hopeful my carb is ok. I’ll check it next week when back from the Reno air races. Cheers BUDFIVE

[wbulk]

BUTFIVE,
If your anti backfire valve is OK you can just close the secondary screws and the rear barrels should run OK off of the idle hole under the transfer slot. That is the way a 4160 and a 4150 two idle system works. You just won't have any fine adjustment unless you change the idle restrictor jets but it should be pretty close.

[BUDFIVE]

Wayne, cool, that’s what I thought. BUDFIVE

[BUDFIVE]

Wayne, SJDave,
I think my QFT 67318 brawler is ok. There’s only one air hole below the transfer slot on the secondaries. And, there seems to be a spring under the check ball so it’s pressed to the top and doesn’t rattle up and down when shaking the carb. You can kind of see the spring in the pic, circled. Can’t quite see the ball with that angle but it’s there. Do y’all agree?

BUDFIVE

[SJDave]

Can't really see the spring very well with the low resolution picture, but it appears there is something in there. Agree, you do not have the extra fuel feed hole in your secondaries.

[Dave Tabor]

I'm late to this thread because I was about to throw my QuickFuel 650 annular booster 4150 in the garbage.

I've got 10+ years of carb tuning experience using the drag strip, wideband AF gauge, etc...but I could not get this QF carb to hold a tune.

At the last Nevada Open Road Challenge this past May (trying to average 140 mph for 120 miles) my engine (Ford 302) would go rich and misfire at WOT in 5th gear. I had to run it at 150 mph in 4th gear at WOT to keep my speed up (~5200 rpm for miles and miles).

Driving since then, the motor would pull best at a bit less than WOT - otherwise too rich. The car always smelled like gas (and me too after driving it). This is after lots of jet changes up and down, all around.

Swapped to an AED 750 4150 and the engine runs great.

So I googled 'why is my QuickFuel carb going rich'...and found this thread.

Looking at the carb baseplate, there is no spring under the check ball and its got the two idle passages.

Ughh...well at least this can be fixed...

Thanks,
Dave
Gen III Coupe #17
217866217867