Carburetor recommendations
 

I'm going to replace my carb soon and was wondering what I should get for cfm. Its a 350 2bbl soon to be a 4bbl.

Get a QJ for the year of your car.Tom

Second.

I've tried that route, cores I have found are junk or over priced. I'm looking into an Edelbroc AVS2.

Contact Sean at SMI and get a price for a done QJ for your application.Tom

If it’s not a restoration why pay big money for an inferior early Q-jet?

Plenty of reasonably priced ‘77 and later Q-jet cores are out there and are a far better design.

This. Get a new carb... it's new and works.

What would the recommended CFM for a 350 be? 500 or 650?

Cliff had been giving his approval, to quadrJet power, in Houston. I'd gat a 77 and up unit from them, as ;art mentioned, get it with an alactric choke!!!

The late ‘70s 350 smogger engines were all equipped with 800 cfm Q-jets.

Hard to go wrong with a late model 800 cfm core that’s been redone by an expert.

The avs2 carbs get rave reviews, I would like to hear back if you try one.

X2 on Quadrajet power… Can’t go wrong

Brent Flynn is still rebuilding QJets and recently did one for me.

There is no "best" carburetor for all applications.

If you want best driveability, fuel economy, power, and reliability; then the Q-Jet, as mentioned by many in this thread, is the way to go.

If you want lots of "wow" from the 16-year-olds at the local car show; then go with the shiny new imitation.

Jon

"If it’s not a restoration why pay big money for an inferior early Q-jet?

Plenty of reasonably priced ‘77 and later Q-jet cores are out there and are a far better design."

+2, 3 and 4.

Since I have no dog an anyones fight (retired from carb building) I'd stay as far away as humanly possible from a Holley Street Avenger (or any of their "bottom of the barrel offerings") and even further away from an Edelbrock AFB or AVS clone. The only good sound any of those make is when I "tink" them off the dumster outside the shop or hit the round trash can by the shipping table with one of my famous "hook shots".

I get locals crawling up here ALL the time with that junk on their "fresh" engine builds BITCHING about all sorts of issues. Then I take a look at the "cobbled" up install where they cut the original fuel line with a hack saw and ran 3' of black rubber hose around to the back of the carb for a fuel supply, often out over the valve cover so it can pick up heat from the exhaust along the way and rub on just about everything it between....LOVELY!

I love stories so here's a good one. Local guy shows up with his engine builder and they can't get their brand new out of the box Edelbrock AVS to do anything right. He is "dead heading" it with a Holley mechanical pump and a regulator and it starts "loading up" after sitting at idle for about 1-2 minutes. I removed it from the engine, put it on my test engine (with a return) and cranked the fuel pressure up to 10, then to 12 psi and it idles fine and doesn't load up or flood at all. Put it back on his dead-headed set-up and clear down to 3psi with the regulator and it floods out. How are you going to fix that? I asked him. He said it didn't do that with the stock mechanical pump but he got a bloody nose when the car nosed over top of first gear because the stock pump wouldn't feed it (454 about 430hp).

He also noted that aside from flooding after it sits at idle for a minute or so that fuel economy is HORRIBLE, and it's got a stumble going into the secondaries that will NOT tune out no matter how tight they wind the spring on the top flap. I ran into the exact same scenario when I drag strip tested them. I was finally able to get rid of the huge stumble by winding the piss out of the spring, but never completey got rid of the noticable transition onto the secondaries. We ran it on two different vehicles on that private track outing and it was the SLOWEST of all 8 carbs we carried along that day, on both vehicles.

I know, I know, go to a car show with 250 cars present and 238 of them will have an Edlebrock intake topped with one of those pieces of bovine excrement, or even worse a Holley Street Avenger.......because they are shiny and cheap.........FWIW.......

A Q-jet will provide the best combination of fuel economy, power and driveability. The triple venturi cluster design on the primary side gives sophisticated fuel delivery that rivals fuel injection when working right. Everything will fit and look right on your Pontiac with this set-up. The Edelbrock knock-offs will run of course, but will require a bunch of "rigging" and "hacking" to make it fit and operate correctly. Fuel mileage will never come close to a Q-jet. They are shiny though, won't dispute that. BTW, tuning parts for the Ederlbrock carbs are VERY expensive and hard to get. Just went through tuning a pair of AFB's and had well over $200.00 in jets and metering rods by the time I had a decent tune on them.

A continuation of my previous post (dog-gone telephone):

Obviously your car, and your choice.

However, the Q-Jet is a "spread-bore" carburetor.

I think the imitation is a "square-bore" carburetor.

USE THE INTAKE DESIGNED SPECIFICALLY FOR THE CARBURETOR OF YOUR CHOICE.

Do NOT just buy the wrong intake, and ATTEMPT to then install the carburetor with an adapter plate and mis-matched mounting gaskets; or your next post might be "I cannot get the idle down to a reasonable RPM" (read as vacuum leak from carb to adapter to intake)!

Take a look at the second line in my signature block (it also applies to intakes).

Jon.

i have a street avenger 770 that i bought a year or two ago, runs great out of the box. just adjusted idle screws and choke.

Cliff - tell us how you really feel ;) :D

How about "equus ferus caballus excretement"?

Jon

No use for the later Holley Offerings. I still buy the older ZINC Holleys at swap meets and have them dichromated after proper prep.
At least there, you can make sure the carbs are not damaged in shipping, (the latest 421 SD intake manifolds had excellent shipping boxes).

Tom V.

+2 on tuning the AFB clones. I had a customer send me two "Marine Q-jets" that turned out to be Webber built AFB Marine clones. Instead of sending them back, which I typically would do if I didn't break them on one of my "hook shots" i decided to dive into them.

Right to start with they had the correct part numbers on them, and original to his twin 454 powered boat. However, when I checked them over closely they were NOT the same for jets, rods, IFR's, air bleeds, etc. So now the quandrum, which one do I copy to make them IDENTICAL units.

Thankfully he had tagged them and noted that his fuel meters showed one fo them using considerably MORE fuel than the other, so I started there. I was able to obtain the same jets and metering rods, and "modify" everything else to make them identical twins. However, on my test engine they didn't run all that great, very rich at idle, and noticable hesitation and overrich condition right off idle thru transition.

So I went into the parts catalog and bought multiple jet sizes and dual tapered metering rods for them and went to work. When I was done they were FLAWLESS, but I had several hundred dollars tied up in tuning components as mentioned above.

The owner got them, and few months later gave me a call telling me that they were also flawless on his end and his fuel economy was a LOT better than it had ever been since he purchased the boat.

Sadly we could have prepared two Marine Q-jets and done better, but his intakes had no provisions for divorced chokes and sourcing out Volvo Penta e-choke Marine Q-jets can be difficult and expensive......

Q-Jet all the way for me.
If I could put a Qjet on my Ford junk I would.
A lot of years back when I did my first 455 I asked Cliff for some tips/tricks because I have been doing stock rebuilds on Q-Jets for a long time with great success but didnt have much knowledge of doing performance modifications to them.
Cliff happily obliged and told me how to do some things which I did and my rebuild/ Modified Q-Jet ran flawlessly and out performed my box stock Holley in every way.

Ford used some Q-Jets in 1970 and 1971 on the 429.

They also used TQ's on some of their 460's

Jon

I was/am having very good luck with the Brawler from Quickfuel. YMMV

We seem to have deviated "slightly" from the original question (as we often do).

OP - many of us have suggested the Q-Jet. One reason is that it is a "spread-bore" design. By 1970 (well, 1972 for Chrysler products) ALL US producers of automobiles had adopted the spread-bore design for virtually ALL V-8 engines, because of the features I mentioned in my first post.

Exceptions (square bore design) were used only on engines that the manufacturer knew had a good chance of being raced (street driveability of less concern) or trucks which would be on the primary side with lower vacuum than a passenger engine.

Give some consideration to the reasons ALL of the car companies went to the spread bore design.

Again, your car, your choice.

I have a spread-bore on my own 350 Pontiac, a Carter TQ, and I have 150,000 carbs to choose from (none of which are imitations); so really believe in what I have recommended to you.

Jon

Rob, that night I came over with my GP to your house, I thought you showed me a Qjet for your car you had already?
Jeff

"Ford used some Q-Jets in 1970 and 1971 on the 429."

Those were and are EXCELLENT units. A factory "hot rod" carb right off the bench. The intake Ford made for them was also a really nice part, with wide plenum areas and very well design runners for effectively feed the 429CJ engines.

One can learn a LOT from looking at what the factory did on their "high performance" Quadrajet carburetors. The Pontiac Ram Air, HO, Super Duty, Buick Stage 1, 1969 Chevy 350/350hp, and a few others fall into that catagory........

"Cliff - tell us how you really feel "

Jon If you haven't noticed I'm quick these days to talk bad about things, which at times may include certain parts or the work of others. Back when I was building carburetors I didn't feel right about bad mouthing anything where it looked like it might be competition, or trying to steer work in my direction, etc. These days I just might tell you EXACTLY what I think about something. I also have bad cases of CRS, and even worse cases of DGS.....that's "Can't Remember Sh*t" and "Don't Give a Sh%t". With all that going on I'm pretty much smiling all the time these days!........LOL.....

On a more serious note, when it comes to carburetors the very best carb is going to be the one you spent enough time with to dial it in EXACTLY for your application. It still makes sense to spend your hard earned money in the right places, so there are options out there that just aren't that great, and other options that aren't worth two squirts of duck poop no matter how much effort you put into them.

No big secret that I absolutely HATE the ever popular Edelbrock AFB clones. Not because you can't findle around with one and get it pretty well dialed in for what you are doing. It will start well and move your car effectively from point A to point B. I hate them because there is not adjustment for the opening rate of the secondary air flaps. So IF they hesitate, stumble, bog, backfire or puke all over themselves going quickly to full throttle there is nothing you are going to be able to do about it. There is also some "cobbling" involved with installing them on some set-ups. I've had fuel line hitting the bottom of the air cleaner base issues, and difficulty running a hard fuel line to them as they are really wide in and the fuel inlet is in the left rear. Otherwise pretty easy to get dialed in if you don't mind giving Edelbrock another pay check for the tuning kit(s).

I've also ran the gauntlet with the Holley Street Avengers and not fond of those at all. They have several fundamental issues which I'll not dive into here, and just not very well made. I've had them come in here delaminating, or basically flaking off internals that are in contact with this new fuel. For sure a notch better than some of Holleys bottom of the barrel work, but certainly not even close to the HP line up. It also appears that Edelbrock now has developed and is pushing another Holley "clone". At a glance they did their homework and addressed every area that needs attention, and put an removeable bleed at every location. Time will tell how they will sort out and fall into the market, but for sure I'd look at those WAY before the shiny Holley cheap offerings.........FWIW.....

Its a chevy carburetor

Oh, I thought you showed me a BOP with the intake you had

Cliff, just a reminder, you already know this:

The vast majority of the Holley Dominator 3 circuit carbs over the years were converted BACK to 2 circuit carbs Holley Dominator carbs and went quicker on the track after the Modification.

Tom V.

I installed a edelbrock intake and a 600 performer carb, it runs good and seams to have woke up the engine.

Thank you for updating the thread.

It is your car, and if you are happy, that is all that really matters!

Jon

My only advice is to check and double check the credentials of any so called "expert" if you have anyone rebuild one for you. I am in a 4 month ordeal trying to get my quadrajet back from a guy. Also that quadrajet is replacing a Edelbrock 750 cfm , my buddy has almost the same motor/tranny setup and is always getting better fuel economy with his QuadraJet then I am. And his car runs hard with the QJ. if your interested in an Edelbrock I have one I will sell if I ever get my QJ back.

Mopar even used em on their police 318`s and the 360 truck engines before they went to the Magnum engine.

Edelbrock's AVS2 also comes in a spreadbore configuration (1912/1913 Series).

Looks like squarebore to me.

https://www.edelbrock.com/catalogsearch/result/?q=1912

Same square flange dual bolt pattern crap they've been pushing for decades. Sales were never what Edelbrock wanted on the AVS versions even though they have a fighting chance of working when you go quickly to full throttle. The poor sales were only because of the nearly double price point compared to their AFB clones. That fact cause the demise of the excellent run of Q-jets they made for a few years. Who's going to pay over $500 for an Edelbrock 1910 850cfm Q-jet when you can buy two of their POS AFB clones and still have some money left over for a Big Mac and a Coke? To me this indicates how cheap the majority of hobbyists and enthusiasts are when it comes to this sort of thing.......IMHO......

The OP made a good choice with that 600 cfm carb. That can fill the needs of up to 380 Hp motor very well.

If you want few more top end HP add a K&N sub stack and even with a 600 cfm carb you should be running a open 3 & 14 air cleaner.

You may need to go to fatter secondary jets with the sub stack.

Wow, never knew how this carb would get all the carb guru's upset, Cliff, have a cup of coffee and relax LOL.

I'm not upset in the least.

When I see these threads I'm quickly reminded how many thousands of calls and emails I've had to the shop from folks who absolutely HATE the Edelbrock junk and despite spending another $100 on their tuning kit can't get it to work for chit no matter what they do.

Since I'm retired and have no dog in these fights I just call it like it is from decades of experience with these things.

Matter of fact we have one Edelbrock POS AFB clone in the family. My brother has one on his 1978 GMC grain hauling truck. It's powered by a 427 tall deck Chevy truck engine and over 20 years ago the governor controlled Holley took a crap on him. At the time the best viable replacement (it was harvest season and he needed it to work) was to buy an electric choke Edelbrock Performer series carb for it. It starts, runs and moves the truck around just like it's supposed to, sucks TONS of fuel but who's keeping track when you are hauling close to 50,000 pounds of grain with it. Every 2 to 3 years I get the unfortunate pleasure of having it dropped off here for a top gasket, new N/S assemblies and a complete accl pump assembly.....it was just in here about 4 months ago.

I stock a kit for it to save down time. Takes me about as long to get it back in service as it did to type this. It ends up here for one of two reasons, flooding and/or no pump shot. The soft silicone pump seal Edelbrock imports for those doesn't last long in this new fuel and the pump is a hoaky POS right to start with being made out of soft plastic and the pump end rotates all over the place like it's worn slam out even when they are NIB.

Anyhow, I put the info out there based on direct experience with these things. Like it, don't like, agree with it, don't agree with it, make a copy and use it for toilette paper I could really care less.........IF it helps someone along the way it was worth the effort.......

With some 40+ years of experience with these things you may learn the benefits of different carburetor designs.

Kenth, I work or have worked on just about EVERYTHING here so my experiences go far beyond one or two different types of carburetors.

I also do a LOT of carburetors for small power equipment, generators, chain saws, string trimmers, garden tillers, etc. I also do quite a few tractor carburetors. I've also built a good many AFB (Webber) clones for Marine applications as they replaced the Quadrajet Marine carburetors in the mid 1990's.

I've dyno and track tested Edelbrock AFB and AVS clones and not impressed with them anyplace. Even with that said if you want a carb that will move your ride from point A to point B with relatively decent success till it takes a dump they are fine for that.

Here's the down and dirty with them. The brass floats sold for them are crap. I've had a 100 percent failure rate with them leaking and sinking to the bottom of the bowl. Some sink right away, others may be a few months or years but the soldered seams aren't that great or this new fuel is eating their lead freee solder, not sure.

They accl pumps are very poorly constructed and the seals are NOT ethanol compatible despite what they are advertising. They are a soft silicone type product, not an elostomer designed to be resistant to fuel with alcohol in it. I suspect the tips of the fuel inlet needles are also NOT made from a high quality flouroelostomer as they fail as well. Not nearly as often as the pump seals but I've had a good many of those carbs in here flooding from that issue.

Some "cobbling" is also involved with the installation. Most folks just hack saw the stock steel fuel line or slightly better cut it with a tubing cutter. Then they run 2-3' of rubber hose back around to the fuel inlet held in place with a couple of hose clamps, not taking care that it doesn't rub on something in it's path. NO ONE takes the time to even put a bulge on the cut steel line so it's not an engine fire in the making.

Since the factory calibrations aren't that great and they have some design flaws included the user ends up another $100 or so in one of Edelbrock tuning "kits" or at a minimum tuning parts to get them dialed in. Wouldn't surprise me in the least if they don't count on that happening as they get another nice bonus on each one they sell. On a good note the primary side is super easy to tune as the PP assemblies and primary metering rods/pp springs are easy to replace with a nice selection of two-stepped rods for that purpose.

They are square flange and often require an adapter or different intake. Edelbrock is counting on the latter to make another couple hundred bucks on the sale. Many factory and/or drop base air cleaners have trouble clearing them, so more cobbling for many Ram Air, Shaker or Cowl induction equipped cars.

I'll stop there, going to go out and spend my time doing more important things like throwing a few sticks for my dogs........

I've seen a lot of these Edelbrock AFB carbs on many cars for years now. I guess because they're cheap and readily available, many people have them regardless of the performance flaws!!!

Every Autozone and OReillys in the country stocks one of the E-AFB's. That's a bunch!!! The Holley 1850 used to be the default stocked carb.

When I try to explain to some folks, along the lines of what Cliff said in post 29, they look at me like I'm BSing them...

That's true Jack, they are everywhere. I've seen my fair share of them here. Usually the car is here for something else and I pray they don't mention carb issues, lol. Because honestly I don't care to dinker with them or the cobbled up mess they've done to install it. Right off the bat they usually require another $100 spent for tuning parts, as mentioned already, and owners already squirm when I mention just that. Basically because the owners are cheap anyway, that's why the carb is on there in the first place. Most owners only care about getting from the house to a car show anyway.

When I was deciding on what carb to use I asked lots of people what they're using and how they thought it worked for there application. Thats what my decision was based on, not because I'm cheap.

Wasn't meant towards you specifically, it's just what I see in general from my own personal experience.

For what you're doing those smaller eddy carbs generally work ok on stock type engines so you'll probably be just fine. It's just the general consensus of those carbs overall isn't that great.

I bought a total of one AFB's. It was a new Carter 625. Installed it on a mild SBC. It ended up working pretty good. That was after throwing the full tuning kit at it. Fought a secondary transition stumble.