What's the latest and greatest "runs out of the box" carburetor?

[NiceGuyEddie]

I've changed my fuel bowl gaskets several times over the past 15 years and at least three of the threaded holes in the casting have been repaired with inserts. I recently gave the the fuel bowl screws a 1/8 turn and you can feel that they are not not holding well. The fuel bowls are just leaking too much and I'm tired of cleaning up the residual fuel.

I have a Holley 570 Street Avenger from my old 306 but I know that with my 347 I should really be running a 650 or 670. I can't imagine the car being any faster, but that's another story.

The Street Avenger used to be marketed as "runs right out of the box" and for the most part, this was true. I went for a dyno tune with my old 306 and only minor adjustments were made, which included changing out the spring in the vacuum advance.

My carb has manual choke, but the plate has been completely removed. Starts easily and idles perfectly smooth at 650rpm even when it's 32° outside.

I have Edelbrock Victor Jr. intake manifold if that matters.
I have a Master Brand electric fuel pump E2025 from an '84 Mustang if that matters.
I have a ??? psi fuel pressure regulator if that matters.

:eek:

[Hellion]

My favorite "out of the box" carb is an Edelbrock 1407/1411 (750 cfm without electric choke and with, respectively) that should pair nicely with your 347.

[RoadRacer]

My 2c (and everyone will have diff answers) - the brawler is way better than any edelbrock or holley ones that I've tried recently.

https://www.summitracing.com/search/part-type/carburetors/product-line/quick-fuel-brawler-street-series-carburetors

They're literally holley clones but (for whatever reason) work better - out of the box.

I have a 650dp

[jamminj]

I agree with hellion
we are using I believe a 650 on my friend's corvette (383) and his nova (350) medium power band cams
easy to tune with an O2 sensor
we are also using this cool distributer

https://www.youtube.com/watch?app=desktop&v=rQJhKbMap_w

[jamminj]

we have 2 on our Chevy's and the work perfectly
this is the link for 289/302 distributer
https://progressionignition.com/shop/ols/products/ford-small-block-289302-v8-small-cap-distributor

[Jim1855]

All depends on what you are looking for and what your budget is.

I've used Pro Systems and been pleased. Many friends have as well.
These are Holley based.
https://www.prosystemsracing.com/crate/

I'm currently running a 780cfm Road Race / Circle Track version. A friend with a 462 ci switched to my 780 from his Holley (?) 750 Vac carb and noticed a significant difference in the power and "snap" throttle response.
https://www.prosystemsracing.com/blaster1/

But looking at going up a size to 850cfm and this version looks good
https://www.prosystemsracing.com/venom-vx-circle-track-road-race/

There are other good makers. The upper end Holleys are working well, the newer https://www.fstcarb.com/ look good. I've not been a Quick Fuel fan but many like those as well.

I've also run both the 670 & 770 versions of the Holley Street Avenger with vac secondaries & auto choke. These ran well with the 670 being a bit more drivable in the lower RPM range, the 770 had a bit more power in the upper range w/o significant loss in low end manners.

I don't run a choke or the airhorn and have found that 1-pump and start is all that is generally needed. It is necessary to feather the gas for the first few minutes when cold. Once warm it was turn the key.

A Double Pumper is the only option I'd look at. Vac carbs are for fat cars.

Now about plug-n-play, I wouldn't hold my breath. The new carb will run but will run better with good tuning. I've heard similar about new Coyotes and EFI tuning.

Jim

[Avalanche325]

I've changed my fuel bowl gaskets several times over the past 15 years and at least three of the threaded holes in the casting have been repaired with inserts. I recently gave the the fuel bowl screws a 1/8 turn and you can feel that they are not not holding well. The fuel bowls are just leaking too much and I'm tired of cleaning up the residual fuel.

I have a Holley 570 Street Avenger from my old 306 but I know that with my 347 I should really be running a 650 or 670. I can't imagine the car being any faster, but that's another story.

The Street Avenger used to be marketed as "runs right out of the box" and for the most part, this was true. I went for a dyno tune with my old 306 and only minor adjustments were made, which included changing out the spring in the vacuum advance.

My carb has manual choke, but the plate has been completely removed. Starts easily and idles perfectly smooth at 650rpm even when it's 32° outside.

I have Edelbrock Victor Jr. intake manifold if that matters.
I have a Master Brand electric fuel pump E2025 from an '84 Mustang if that matters.
I have a ??? psi fuel pressure regulator if that matters.

:eek:

How much HP do you expect from your 347?

A 350HP 347 and a 500HP 347 won't want the same carb. Carbs feed horses, not cubes.

I have a QF Q-Series 750 on a 500HP 347. That is mechanical secondaries and no choke. It ran "fine" out of the box. However, I did a lot of tuning, and I have better throttle response, and I am not lean up top.

Most carbs will run right out of the box with just setting the idle mixture. You could be leaving something on the table performance-wise. You could also be putting a hole in a piston if it just happens to be lean.

[GoDadGo]

I'm running an Edelbrock AVS 800 on my 383.
The current version has annular primary boosters.
It sits on top of a Team-G Single Plane intake and works well.
I'm making over 460 HP with similar torque figures so it really scoots.
All I've done is set the timing, idle adjustment mixture and the secondary flapper.

Link To Redbone's Graduation:
https://www.factoryfive.com/whats-new/customer-steve-l-graduates-his-mk4-roadster/

[NAZ]

Living at sea level, you may get an out of the box carb that works good enough for you. But there is no out of the box carb that is perfect for every application it is intended for, therefore, if you know how to tune a carb you can get the most out of your selection.

I used to make my living tuning carbs for other people and have been tuning a variety of carbs for six-decades now. By far the most popular performance carb is the Holley 4150 Double Pumper and its clones. My preference is the QFT version of the 4150 as it has more tuning capability than the original and other clones. It is made by Holley and has a great deal of support. Get yourself a book on tuning Holley carbs. For a simple metering device, the physics behind how a carb works and how a 4150 works can be daunting to the average hot rodder. I find it fun and rewarding tuning carbs. Expert carb tuners are getting harder to find -- we're getting older and most of us are long since retired. You will likely have to do your own tuning so if you want to stay with a carb, go to school on them and learn how to do your own tuning.

Here's your first lesson: https://www.holley.com/support/carburetor/

[GoDadGo]

Oh-Yeah, I forgot to mention that I typically drive between 5-35 feet above sea level to as much as 5-15 feet below sea level.

With that little tid-bit out of the way all I can say is:.. Hit It Harry!

https://youtu.be/gHakdT1F8As

[Papa]

Nobody has mentioned Demon carbs yet. I haven't fiddled with a carb since selling my 1970 El Camino with a Chevy ZZZ 350 crate engine. When I got the car from my dad (near seal level) and brought it to Colorado, it was running really poorly with the Holley 750. I took the car to a carb guy and had it re-jetted and tuned and it was better, but still rough at cold idle. I replaced the Holley 750 with a Demon 650 and that made a huge difference out of the box. I recall Demon carbs being very well liked at that time, but things may have changed since then.

[NiceGuyEddie]

I didn't want to hijack my own post, but the 347 came with a Holley 850cfm Double Pumper. Forever a mystery. It needed to be tuned as it bogged when going downhill, even on a curved freeway onramp. At the time, I was strapped for cash so I sold it to a forum member and put my 570 back on.

My 570 will stall the engine completely on a hard stop to 0mph if the car gets pulled out of gear just before the stop. When I go to Autocross I have to raise the idle to 1,000 rpm so I don't have to think about it. Hoping a different carb (or ???) will remedy this issue.

[nucjd19]

850cfm for a 347 is pretty darn big. IMO the sweet spot for that engine is 600-650cfm. I have a Holley 600cfm carb on mine and it runs like a top. I plan on pulling my plugs in the next couple of hundred miles and take a look at them.

[NAZ]

I didn't want to hijack my own post, but the 347 came with a Holley 850cfm Double Pumper. Forever a mystery. It needed to be tuned as it bogged when going downhill, even on a curved freeway onramp. At the time, I was strapped for cash so I sold it to a forum member and put my 570 back on.

My 570 will stall the engine completely on a hard stop to 0mph if the car gets pulled out of gear just before the stop. When I go to Autocross I have to raise the idle to 1,000 rpm so I don't have to think about it. Hoping a different carb (or ???) will remedy this issue.

If this is an overly rich condition, a common causes of this condition is fuel slosh exiting the vent tubes and down the carb intake. When under hard braking, the fuel can slosh out the rather short vents and enter the carb intake causing such a rich mixture the engine stumble or even die. The fix is to extend the height of the tubes but never extend them closer than 1/4" from the top of the air cleaner and more space is better. A piece of rubber fuel hose can be slipped over the existing steel vent tubes to extend them.

This is the most common cause of this symptom but is not the only possible cause.

[nucjd19]

If this is an overly rich condition, a common causes of this condition is fuel slosh exiting the vent tubes and down the carb intake. When under hard braking, the fuel can slosh out the rather short vents and enter the carb intake causing such a rich mixture the engine stumble or even die. The fix is to extend the height of the tubes but never extend them closer than 1/4" from the top of the air cleaner and more space is better. A piece of rubber fuel hose can be slipped over the existing steel vent tubes to extend them.

This is the most common cause of this symptom but is not the only possible cause.

NAZ this info right here is worth its weight in gold. I always appreciate your input.

[NAZ]

Back in the day, we used to extend the vent tubes on our off-road vehicles as bouncing around the desert does the same thing. Either hard tubing or or hose looped.

164178

[Jim1855]

Mine wasn't fuel slosh. Tried all the tricks, vents, whistles, extensions, bumping idle rpm and more.

Had to modify the metering circuits, performed by a carb tuner. I don't really understand the cure but it worked.

Jim

[J R Jones]

850cfm for a 347 is pretty darn big. IMO the sweet spot for that engine is 600-650cfm. I have a Holley 600cfm carb on mine and it runs like a top. I plan on pulling my plugs in the next couple of hundred miles and take a look at them.

For what it is worth. Back in the day my Shelby GT350 street and BP race car, ran the same engine and carb as the BP Cobra. 289ci with a Holley 715 CFM and mechanical secondaries on an aluminum high riser.
Eventually I converted it to a double pumper, but IT IS HARD to evaluate how much it changed, season to season.
We ran a 800 CFM on the (racing) Boss 302.
Interestingly I ran one season in a CP Sunbeam Tiger with my 289, but I had to run a two barrel 650 CFM on a cast iron low riser manifold. No one had run a Tiger in the Central Division in years and it upset the class with pole positions, wins and a lap record.
jim

[NAZ]

Selecting the proper size carb for the application is a science and most tend to go bigger than optimal. But some engines act bigger than their cubic inches would indicate. In some applications, bigger really is better.

I run a 1050 CFM QFT on my 406 that makes peak HP at 7500 RPM. Running the calcs, I could theoretically pick up 5 lb ft of torque at 6000 RPM (convertor stall speed RPM) and 4 HP at 7500 (peak power) by going to an 1150 CFM carb so 1050 CFM is close to but not over the optimum CFM. I selected the 100 CFM smaller carb as I wanted to stay with the 4150 style carb as I have lots of $$ tied up in change parts for the 4150 so an extra 5 HP was not worth the added cost to run the Dominator style.

And the engine idles, accelerates without hesitation, and runs like a scalded dog at any RPM and any load on the street. That's because I selected my intake and heads to maintain higher mixture velocity and my volumetric efficiency runs between 119% & 118% @ WOT within the engine's operating range of 6000 - 7500 RPM so the engine acts bigger than it really is. And of course, the carb is modified and tuned to optimize performance over a wide range.

Select all the components so they complement each other then tune the assembly properly and the result is a powerful engine that is easy to live with on the street.

[AROCK]

I have used Prosystems Carburetors for over 20 years on my Drag cars and love them. I ran a 1000 cfm ProSystem 4150 on my 509 cubic inch drag truck and ran consistent times year after year.
The ProSystem Carburetors are made for your engine specification, trans, and rear combination. The carb will come and bolt to your engine ready to go. You may have to make a jet change up or down but I
The carb is literally ready to run.
I just had Patrick from ProSystems make an 850 cfm Venom Vx for my 427 stroker I built for my FF Roadster. Give them a call you will be happy.

[J R Jones]

The OP here is requesting a "plug and play" solution. That is a concept more easily accomplished in electronics, fuel flow not so much.
NAZ effectively addresses maximum flow/power circumstances, but I will pontificate a bit on drivability.
Unlike EFI, the carb is like a spray gun. The fuel is static and the air is dynamic. As the engine draws air, the carb reacts by siphoning fuel out of the bowels and letting it atomize in the carb throat. There is no anticipation for increasing throttle opening / increased air flow, and to compensate the acceleration pump sprays raw fuel into the throat to mask a lean circumstance from slapped-open throttle plates.
Sequential vacuum circuits attempt to match fuel siphoning to throttle opening coupled with jet variability from metering rods. It is not perfect, but it works.

It may seem counter intuitive but too much carb size is problematic at lower and mid range. The engine is sucking air and the larger the carb, the slower the air velocity in the carb throat. Slower air does not siphon fuel as effectively as high air flow rates. It is referred to as "the signal". The advantage of the four barrel carb is running on two throats with high air velocity at lower RPM and four throats at higher speeds. The throat sizes can be the same or staggered to emphasize air velocity at lower speeds. The options for tuning are mostly jets, rods and orifices. O2 sensors offer insight into the process. I prefer to resolve drivability before maximum power, the former being more difficult.
jim

[Ford & Jeep Fan]

My favorite "out of the box" carb is an Edelbrock 1407/1411 (750 cfm without electric choke and with, respectively) that should pair nicely with your 347.

Agree 1000% on the Edlebrock (AFB style) carbs. When/if you think the carb is not perfect for you, buy a Carb jet/spring kit I looked don't see them at the moment. I'm sure they still sell them. they come with a little book to show you all the factory jeting with a nice little graph and the many possible changes you can make.

If you want to race get a Holley. (Great at Wide OPEN THROTTLE) How often are you at WOT?

If you want to cruise down the road get a Edlebrock AFB type carb.

[first time builder]

For out of the box and no leaking bowls, go Edelbrock 1406. No real reason except for past usage.

[Railroad]

If you can find the shows, Engine Masters, or that other one, little guy named Pat something, both have informative test using different carbs. One show was about the best performing carb for the money and other related to carb size and performance. Both test blew some shop talk theories out of the water.
Believe me, it is worth the effort to look up and watch the videos.

[BradCraig]

I liked the AVS2...before I went to EFI. :-)