I have a hard time accepting that a 305 can’t open the vacuum secondaries on a Holley unless this Holley is so big that the primaries are sufficient like if this is an 800 to 1000 CFM carb.

That said the AVS-2 is the closest thing in the contemporary world to the Q-Jet. The AVS also sometimes called the Thunder has an adjustable air valve above the secondary venturies which is different from the AFB Performer which uses a non-adjustable valve below the secondary venturies. These things range at 500, 650 and 800 CFM choices.

Bogie

 

You are exactly correct about the Edelbrock being just a straightforward out of the box best choice. Back in the '60s I had a Carter AFB in my 14 ft flat bottom boat that had a Chevy 350 in it. I ran it for 20 years roughly never had to blink an eye at any problem or even took it off the intake manifold to do anything to it. As you probably know the Edelbrock carburetor is basically a Carter AFB.. I built a big block 454 for my '69 Camaro number of years ago and chose to use a Holley but it was nothing but trouble. Never did get it tuned very well and it constantly would spring a leak if I didn't start it up every week due to the paper gaskets on the bowls springing a leak. Edelbrocks don't leak. They are super easy to tune with nothing but rods and jets to consider. Mechanical secondaries and electric choke work just fine.

 

Put your Edelbrock back on. If it runs better, you win!
Use what you have, but I would not buy another one just for that 305.
Save your money. Put it in a sock somewhere safe. Before you know it you will find a 350 to plop in!!

 

Put your Edelbrock back on. If it runs better, you win!
Use what you have, but I would not buy another one just for that 305.
Save your money. Put it in a sock somewhere safe. Before you know it you will find a 350 to plop in!!

I don't have the old Edelbrock, returned it to get money for this Holley, being told that Holley was a lot better.

I'll have to dump the money in to buy a new one here in the next 72 hours.

Either way I'm just getting tired of finnicking with the Holley.

AVS2 or Performer ? Which takes E10 better ?

 

Usually Holley's work pretty good out of the box too on fairly mild engines.
If you buy another smaller carburetor now, be prepared to buy another one when you put your 350 in it down the road.

 

Yeah I was thinking about that, I also thought about keeping this Holley carburetor to use for the 350 but I would want something bigger than a 600 CFM so I've prepared myself to buy another carburetor when the 350 or bigger is ready to be dropped in and everything else is ready to be replaced on back.

 

That 600 really should not be too terribly bad for your 305. Have you considered getting an air fuel gauge to see where you're at on the tune?
I haven't been messing with carburetors all my life, and that's the only way I can get mine running right!
It sure does make it easy.

 

Yeah I was actually considering that as this month's project..an AFR gauge.

I usually tune my carburetors with a vacuum gauge though. And AR for our gauge is good for when you're driving and want to see what your AFR is while you're driving.. from what I understand.

However the main reason why I want to switch carburetors is because of the vacuum secondaries that I have on the Holley... I would rather deal with mechanical secondaries and be done with it.

 

Let me just say that Holley is not better then Edelbrock and vice versa. They both have there place and pros and cons on tuning and making them work well etc. Like that I have told you in other posts you need to take time and research and "study" on how a carburetor works and functions and better understand what your getting into too. I was once green like your are when it comes to tuning a carburetor. I went from being 18 years old back in the early 90's and did not even know how to turn an idle screw let alone anything else and check and fill fluids to learning how to tune a Holley carb for all kinds of builds from mild stock cams too wild big cams.

I also learned how to build my first engine and not have to be told what to do and follow my Father on assembling things and checking proper clearances and blue printing stuff. I am still learning after about 15 years of digging into things and stuff. An Edelbrock style carburetor is somewhat easier but you still need to understand how it functions and what it is your needing to tune and what areas to change on.

Even as simple as they are compared to a Holley, you can still get lost fast if you don't know what your doing and understand where your going with it. Get books and do research and watch videos and take your time. I guarantee I could get your Quick fuel carb tuned really well within a few hours doing a few changes at a time. Also as far as buying rebuild kits goes they are both similar in cost and stuff as it depends on what kit you get for a Holley carb. Some comes with more extra parts vs some other ones and also from where you buy it at.

Also on the vacuum pod there is three ways it comes from Holley or quick fuel and how it functions. The older Holley brand pods used to carry a check ball in them and it acted like a signal restrictor to allow the secondary side to not open up too fast and to also not slam shut. In order to cut cost and improve things somewhat Holley replaced it by placing a brass restrictor in the feed port to the pod. The brass restrictor acts just like a jet does and restricts the signal going into the pod. The problem with it and the older check ball design is you can't adjust anything.

In the older days some folks would take the check ball out but it would create a problem to where the secondary side would open way to fast and without the check ball you could not fix it. It was a hit or miss and not the best way to go about things in certain conditions. Then in later years Quick fuel before being bought out by Holley created there own adjustable pod and with the adjustable pod if they left the brass restrictor in place and then with the adjustable screw topper you would then have two restrictions in place and not function properly and be held back.

So that is why that pod has no brass resctrictor and the adjustable screw allows you to get the proper adjustment rate and fine tune it according to engine needs and proper spring color being used etc. That Quick fuel carb could be made to work well and just because you replace it with whatever Edelbrock carb your get does not mean your going to all of a sudden get secondaries to open up like a Holley double pumper and just get wide open throttle on the whim with all four barrels open up. They act just like the same as a Qjet does and only opens up to demand on what the engine wants.

The Edelbrock AVS-2 650 would be more then enough for your little 305 and its better then the Edelbrock performer carb as you can adjust the secondary opening tension and also it has annular boosters for better fuel distribution and atomization. I hope you just don't go out and buy another carb just to get disgusted with it and think its bad and no good. I once started out loving Holley carbs on a bone stock 350 motor back in the early 2000's which was before I knew anything about motors and then I got the Hot Rod performance bug hearing a engine with a rumpy rough idle sound and wanted my engine to sound like that.

Long story short and thousands of lost dollars later and to many hardships to talk about and wasted time and parts told and rebought and ended up hating Holley carbs I switched to Edelbrock only to have the similar problems that I picked up along the way by not doing things better and right. I took the time to sit myself down and start to not have to depend on others for every simple thing there is about carb tuning and thought to myself I need to really dig in and learn how to tune these if I am going to get the best out of any brand of carb I use.

I started that back in 2008 by coming on here and still have had to learn some new advance tricks along the way on Holley carbs. I am not trying to knock you down and mean nothing disrespectful but you are just trying so many things at one time you can get lost and frustrated and make yourself think something is no good when its not and you just have to learn how to work with them and what you got over time and be patient.

If your going to change carbs then I recommend getting a book on tuning whatever Edelbrock you get and then get a proper tuning kit etc so you can dial it in like you need to and do research on different tuning problems and just read up on some things and jot down some notes on what worked for that person and start to put two and two together and you will then be able to trouble shoot a lot of things for yourself and gain experience a lot quicker and be better ready to issues when they come and trust me they will. Best of luck to you and hope you can find that good spot for a carb.

I think at this point your frustrated with your 305 and are looking for power that it just does not have and won't ever have unless you spend a ton of money on better flowing heads and a complete rebuild but at that point a low budget crate 350 would be the better investment over the long haul but your engine never the less has seen better days and is tired and you can't make it what it never was to begin with by even just changing heads on it.

My 350 I mentioned above would never make even close to 500 ponies with what I got in it and don't expect it too and know its limits and don't try to go past that. Try to take some time and rethink about what direction your going and is it going to be worth while before spending more money on stuff only to still be unhappy. Trust me I have done that so many times I could write a book about it. Best of luck Tynan

 

AVS-2 but make sure you decide on a mechanical choke or electric; you cannot convert an AVS-2 from mechanical to electric.

Heres a Non-EGR, elec choke, 650cfm thats factory refurbished
Edelbrock 19069 Edelbrock AVS2 Series Carburetors | Summit Racing

 

I like mechanical because I'm in control of it when I need to.

 

Below is one for way less then what summit is asking. Its a refurbished one and electric choke for $240 plus shipping.

Edelbrock Remanufactured AVS2 Carburetor 650 CFM Electric Choke #1906 | eBay

REMANUFACTURED EDELBROCK CARBURETOR. Edelbrock #1906. This unit is re-manufactured by National Carburetors, not Edelbrock. then re-assemble the unit with a Edelbrock rebuilding kit. 650 CFM ELECTRIC CHOKE.

www.ebay.com

 

Also one last word to note on the Edelbrock carb which ever one you get, make sure you have a fuel pressure regulator and set it only at 4.5 to 5 psi max as they are way more sensitive to pressure vs a Holley and also you might need to invest in a heat insulator gasket as they at least in the summer time are prone to getting to hot and boiling fuel over. In the winter time in cold states naturally they would not be needed at that time.

 

I run an older AVS-1 on my 350. It’s a pretty warmed up engine with LT4HOT cam and LT1 heads with about 10.5 compression. My 800 Thunder AVS has never needed a lot of monkeying around. It was used so I put a kit on it and replaced the floats as the previous owner caused a float to leak by improper adjustment method hint here is own and use two needle nose pliers for adjusting don’t just twist the hinge tang from its end. The only mod I made was to jet both sides up one jet size as a CYA for the high compression so I threw some extra gas at it for in-cylinder cooling as I have to deal with mountain grades and a climate from cool and wet at sea level at home to hot/cold dry desert depending on the seasons on the other side of the mountains. The extra jetting doesn’t seem to be needed based on driving experience but I haven’t made a jet change back to what it came with.

Yes there are two things the Edelbrock carbs whether AFB or AVS is heat and high fuel pressure. Using a mechanical engine driven fuel pump a simple dead head regulator works fine to keep pressure at 5-6 PSI. An insulating spacer between carb and intake solves the heat issue which given neither of these were needed in the 1960’s and 70’s with these carbs when Carter produced the originals the pressure and heat problems of today probably really speak to contemporary gas blends rather than inherent carb design problems.

Bogie

 

I'm leaning towards to run a 500 cfm AVS2 with the manual choke.

Next question, with the new carb, should I/do I need to buy an AEM UEGO 4110 Air/Fuel Ratio Gauge ?

 

That is the gauge kit. It works good. I have 2 of them.
But if you get a new carb, and it works good out of the box, (it probably will) you can hold off on the gauge until later.
You will have to weld the bung down there by the tranny. Other than that installation is super easy!

 

That is the gauge kit. It works good. I have 2 of them.
But if you get a new carb, and it works good out of the box, (it probably will) you can hold off on the gauge until later.
You will have to weld the bung down there by the tranny. Other than that installation is super easy!

Actually, it's even easier than that. Somebody makes a clamp on bung.

 

The 500 cfm AVS carb would not be too big and would actually give a better throttle response with the smaller throttle bores. Also just to advise you again even though when you open up the throttle by hand and you see the secondary open up, its not a mechanical secondary and the secondary side will only open up by air velocity and engine demand and if there is enough to operate them. The Edelbrock and AVS carbs look like there a mechanical secondary because the secondary side opens up when you open up the throttle but they have a slight difference between the two on how they operate.

The old AFB Edelbrock performer carb has a weighted flap type of a deal that really can't be changed and it will only open up and allow air flow through when enough velocity will pull them open. The AVS is different but it has an air dam type of a door that will not open up till enough air velocity and engine demand will allow it to do so. The AVS style you can adjust the tension on the secondary side to open up easier etc. The AVS secondary side is similar to how a Qjet secondary opens up. Don't be surprised that you don't get much difference when mashing open the throttle but compared to your Holley Quick fuel 600 Brawler carb you have the AVS 500 cfm will have smaller barrels and will have a stronger signal going to the boosters and with the AVS2 having annular boosters it will atomize the fuel better and give more response so you should have some improvement on some things.

With the smaller 500cfm carb and smaller primary barrels it should in theory allow the secondary side to be operated and demanded more since its a lot smaller of a carb and will have a slight stronger signal compared to the Quick fuel carb your currently using. Once you do get it let us know how it goes as I could be curious and would love to see your classic 305 run with that.

 

Yeah I posted the same question in the G-Body garage Facebook group from the G-Body garage YouTube channel.. pretty much everybody said 500 CFM, or at least it was the majority pick.

 

I believe the AVS2 500 cfm carb will work way better overall and is more custom taylored for your little 305 anyways and should give better fuel mileage as well. There is a place for all styles of carburetors and some instances you can have a few options and you can go smaller or slightly bigger but have some sacrifice has to be done on some builds.

I myself with what I have could use a 750 cfm carb and get the most out of it but with my engine being mild and not raced etc and only a cruiser deal I stick with slightly smaller cfm carbs in the 600 to 650 cfm range for the best overall performance for what I do and not for max power etc. With the smaller cfm carbs I use I get the strongest signal I can get for the mid range and below which is where I am 99 percent of the time and also crisper throttle response and stronger signal to the boosters etc.

Always a trade off for some builds.

 

I know this is not what you want to hear , but being me I'll say it anyway ,doesn't matter what you're working on , Instead of throwing money at a problem , LEARN where youre failing . You have to understand what's wrong before you can fix it. I have over 65 years repairing mechanical devices , I still try to learn as I go along ..

 

I've learned it, maybe not everything, but enough..

It's just too much time and confusion to tune and maintain, there's too many different parts and everything is expensive when it comes to those parts.. I've also experienced and do not like vacuum secondaries, and the process of replacing diaphragms and playing with springs.

Edelbrock doesn't require all that, maybe some springs, metering jets, and needle sizes and that's it... adjustment of the secondaries with a screw and torx bit... the rebuild is a lot easier too if needed.

I'm better off throwing money into an Edelbrock once in a awhile then to keep constantly dumping money into the Holley, but I understand and hear where you're coming from.

 

View attachment 631850

But if I already have a bunghole in my manifold, couldn't I just put the sensor in that ?

 

yes

 

Now as far as my fuel line routing goes for this swap...

I'm using rubber fuel line from the mechanical fuel pump to the fuel filter, to the fuel pressure regulator, and then to the carburetor..

I seen this kit on Speedway Motors where they offer the Chrome fuel line adapter for the carburetor and braided fuel line, that I'm assuming it's steel ?

Should I grab this deal with this carburetor to eliminate the rubber hoses..?

 

Now as far as my fuel line routing goes for this swap...

I'm using rubber fuel line from the mechanical fuel pump to the fuel filter, to the fuel pressure regulator, and then to the carburetor..

I seen this kit on Speedway Motors where they offer the Chrome fuel line adapter for the carburetor and braided fuel line, that I'm assuming it's steel ?

Should I grab this deal with this carburetor to eliminate the rubber hoses..?

View attachment 631853 View attachment 631854

If I'm going to convert the rubber fuel lines that I have with still braided and the hard line, I'm going to have to eliminate the fuel pressure regulator and pressure gauge, and inline plastic fuel filter..

If I'm going to do that then I need to replace my mechanical fuel pump with one that produces 6 PSI and just add a pressure gauge at the Hard line 1/8" hole.

Still braided fuel lines should only start from the fuel pump and run to the carburetor chrome hard line, because of the high pressure, correct ? From the gas tank to the mechanical fuel pump I shouldn't have to worry about that, right ?

 

As far as full manifold vacuum routing from the back of the carb...which is connected to the PVC valve on the passenger side valve cover...(is this correct ?)

...And for the brake booster and transmission modulator, I have a tee fitting connecting both on the intake manifold...

From what I understand, brake booster isn't supposed to share another full manifold vacuum source with another accessory requiring full manifold vacuum...is this rule the same for the transmission modulator ?

What might I need to remove around or replace to fit the Edelbrock correctly ?

 

As far as full manifold vacuum routing from the back of the carb...which is connected to the PVC valve on the passenger side valve cover...(is this correct ?)

...And for the brake booster and transmission modulator, I have a tee fitting connecting both on the intake manifold...

From what I understand, brake booster isn't supposed to share another full manifold vacuum source with another accessory requiring full manifold vacuum...is this rule the same for the transmission modulator ?

What might I need to remove around or replace to fit the Edelbrock correctly ?

You have yours set up the same way I have mine. No problems with my brakes or the tranny. I like the crankcase fumes to go in and mix with the A/F coming in at the carb base. Don't know if it makes any diff, but makes more sense to me intuitively. The vacuum modulator for the tranny never calls for vacuum at the same time you are applying the brakes, so you should be OK using that separate manifold connection f for both. Can't help you with the throttle springs question tho.

 

Last question...

Can I use this throttle return spring setup that I have on my Holley, with the Edelbrock ?

 

I would say no

 

I like the crankcase fumes to go in and mix with the A/F coming in at the carb base. Don't know if it makes any diff, but makes more sense to me intuitively.

You mean I should put my pvc on the driver side instead of the passenger side ? I think they are two different size holes on each valve cover.

The vacuum modulator for the tranny never calls for vacuum at the same time you are applying the brakes, so you should be OK using that separate manifold connection f for both.

Yeah this makes sense and I should probably separate them and be better off than having them connected at the same time given that they do not operate at the same time.

 

You mean I should put my pvc on the driver side instead of the passenger side ? I think they are two different size holes on each valve cover..

No. I meant I would use the large 3/8 hose nipple at the base of the carb for the PCV connection. Doesn't matter which side, L or R, the PCV is on. The grommet holes are the same size on both. Use whichever works best for your hose routing. The other hole has to be "air in" either from a breather cap or a hose from under the air cleaner. Your V/C set may have third hole but that's for oil fill, it won't take a grommet anyway, usually , but a screw-in cap. I have my PCV on the passenger side (rear) and my breather on the driver side (front). Works well for me.

 

If there is the same vacuum level in inches/Hg at each source (should be) can't see how it makes a difference. The two sources might vary a tiny bit under load, but I don't think you could measure the diff. I have checked both at idle on mine and they read the same (again, no reason why they shouldn't unless there's a leak at the connector.)
You can try both and see if one setup works better for you. Not unsafe to swap things around. If you do find a diff, let me know!

Yeah I'm going to swap things around and see how things go.

 

Well it isn’t high pressure like EFI uses but even at 5-7psi it is a significant fire hazard.

I run High pressure EFI rubber lines from the bypass regulator to my AVS hard line with a pressure gauge. But my system was designed for high pressure EFI as back in the shop days it swapped between different systems EFI and carbs for testing. I do all filtration ahead of an engine mounted pump, in my case ahead of the bypass regulators since I’m running a high pressure in-tank pump with no filters after the regulators. With a carb and engine driven fuel pump Like yours I just mount filters ahead of the pump. But I also run dual filters plumbed in parallel as this doubles the filtration surface area without forming additional back pressure as would two filters in series.

Bogie

 

Regardless of an Edelbrock or a Holley style carb, if you plan on owning one then you have to invest in the proper stuff in order to completely tune one and get the best out of it. By the time you buy another carb for over $400 to $500 bucks, you can have a ton load of tuning parts for way less to tune the carb you already own along with future ones.

You just have to learn and educate yourself on what your getting into and how to properly tune things. I invested in the following parts to tune my Holley carbs.


Holley accelerator pump tuning kit. $200 Has all pump cams, all shooter sizes, accelerator pump diaphragms, misc hardware and shooter gaskets and check needles and everything necessary for any future Holley carb.
Jet kit $80
Idle air bleed blanks $20 set of 10 blanks
idle feed restrictor blanks $17 of 10 blanks.
Vacuum secondary spring kit $22
Extra metering block and fuel bowl gaskets. Cost varies.
Extra power valves $8 average.

So that is just a little under $350 bucks for enough stuff to tune any Holley for the lifetime that I have own my builds and use any Holley style carb on it. Does it seem like a lot? Yes at first glance but the cost of all that stuff was about half of that 15 years ago and over the last 15 years since tuning them and investing in that stuff and learning how to tune one regardless of a double pumper or vacuum secondary, I have not hardly had to buy anything new for parts wise except for the occasional air bleeds or restrictors and gaskets on the occasion or a rebuild kit here and there for way less then buying a new carb.

The key is patience and time and learning to work with what you have and sticking with it and not giving up so fast and just throwing it out because of not giving yourself time and experience to better tune and have a good idea on what to change. If you are going to go AVS carb then a calibration kit will run you about $85 bucks or more depending on where you buy and if a shooter kit is needed it goes for around $40 plus so right there is a cost of over a hundred plus.

You already if I am correct have a secondary spring kit, accelerator pump cam kit, some shooter sizes plus or minus from .031 out of box size. All you would need is a jet kit and some idle feed restrictor blanks and you could really dial that thing in and run it good. Now for the vacuum secondary not opening up well that is a whole different story there as you might not have it sealing or some other factors going on there.

When I put my 600 Brawler on, after some running and adjustments all I had to change was the jets for mileage, pump cam and secondary spring to a lighter spring and a minor change on the idle feed restrictor size in the metering block to lean it out for my 350. Done in less then two hours.

Your doing a lot of what i did when I first started and before I read books and educated myself better and do one too many things at one time and expecting it to do something that your motor does not have the power and flow to do. Holley vacuum secondary carbs get a bad rap at times on the opening up of the secondaries because they don't take the time to properly tune them and learn on how they function and also think they should be opening up like a Holley double pumper does but that is not how they function and neither does an Edelbrock AVS or Qjet for that matter.

Its all about engine demand and velocity and air flow and rpm and carburetor signal. The bigger the engine and more air coming in the more they will operate and open up more and quicker when properly sized for said build and tuned correctly. The quicker the rpms pick up as well rear gearing and transmission type will also play into things.

Your little 305 and if you have anything like a 2.75 rear end gear ratio then your going to have a hard time getting your Brawler to really need much on the secondary side of things in lower rpm ranges. Even on my 350 with the lightest spring color of white, it takes some 2000 plus rpm to get them to start to open and bet I would have to be up to 5 grand before they would be open up all the way they are going to do for my build and doubt it ever would on yours.

Bottom line if you do get the Edelbrock AVS 500 carb it will be a lot better suited for your mild 305 and with it properly tuned give better results overall with it being a better sized 500 cfm and the design of the AVS2 itself being better suited for a build like yours vs something for performance builds.

Holley has some features that allow for more super fine tuning vs Edelbrocks design but is pretty easy and straight forward once learned and you gain experience. Books and videos help out a lot and stuff. Just like anything if you plan on working and fixing on things you have to invest in tools to do the said job and just like building things, working and building and tuning carbs will need stuff invested into it in order to make it functional and run right along with the rest of the motor.

Its like an art form and needs to be learned just like everything else and will need an initial investment made for whatever carb you use in the long haul and there is no just bolt on and go carburetor ever made. Just like there was never a car made that never needed to be worked on at some point and time.

Edelbrock and Holley are both good carbs to tune with but one just needs to learn how to do one area at at time and in a correct order and also get help from folks who really know what there talking about and a lot of misinformation over the years on the web has not help and carb tuning is a dying art with EFI throttle body injection being the more popular thing nowadays.

 

I am for the new Edelbrock 500cfm carb. Primarily because it has not been jacked with.

Please don't go down the same path of trying to do this and that to it (just because someone said) like you did on the Holley. Try running it as-is.