Are these modern carburetors a big improvement?

[YakkoWarner]

It sounds as though the carb is fundamentally pretty darn limited and fuel injection should be used for greater accuracy and elimination of all those problems.

But what about that old mechanical fuel injection? Can't remember, but I think even back in the 50's there were some vehicles that used that system. They even had 1 injector per cylinder. I guess nobody makes that and you're not going to find it anywhere for sale.

"The oldest known vehicle to use port injection with one injector per cylinder was the brief production run of the Bendix Electrojector system, offered by Chrysler for the 1958 model year. This system featured fuel injectors mounted just above each intake valve and delivered timed pulses of fuel to each cylinder, meeting the definition of true multi-point or port injection."

Well probably the oldest known automotive application of electrically controlled injection. The folks at Daimler-Benz and Messerschmitt refined the mechanical injection systems (which was adapted from the same sort of fuel distributor pump used on diesels) through use on the WWII fighter aircraft. They might have built a few cars using the same basic systems after the war, but likely just as one-offs or race demonstrators, not production models.

Even into the mid 1980s VW was still using the mechanical injection system on the small diesels My sister had a 1980's Rabbit with that system, it was brllliant and got 50+ MPG with no computers or electronics - the only electric thing needed to make it run was enough voltage to open the fuel cutoff valve - which was also the only way to stop it once it got running other than run out of fuel. I expect using a system like that for gasoline was tricky and possibly dangerous with the pressures and potential for leakage.

The other way to get consistant fuel metering is multiple carbs. The inline-6 Triumphs and Jaguars had 3 SU sidedraft carbs so each one had the same distance and path to every cylinder. Of course now that means you have to get each one properly dialed in, make sure all the linkages are moving in sync, etc. It can work, but isn't ideal for the average consumer. On a V8 you could put 4 downdrafts each feeding a pair of cylinders in matched pairs, but the same issues with sync and linkages would be apparent.

Direct injection eliminates all that kind Rube-Goldberg nonsense and failure points, and then they put computers into the system to reinsert the Rube-Goldberg failures electronically instead.

 

[Grit dog]

No.

 

[K5Rob]

Im a fan of Edelbrock (AFB) as the fuel level is below the gasket line, they are easy to adjust things like metering rods and springs, and they typically run good right out of the box. That being said my Malibu which is carbureted had the notorious off idle stumble. Turns out it is very lean for a split moment when dumping the clutch. My research indicates that Edelbrock actually changed the design sometime in the 90s to try to conform with evolving EPA standards. The work around this is to drill a specific jet which is not removable. Once it’s drilled it’s drilled. So to answer your question I might say the older stuff may be better in some cases. YMMV

 

[PhotonFanatic]

Maybe I should have asked, if properly dialed in, are these modern carbs superior to the OEM ones? And if so, how?

But maybe the only time you'd ever notice is if you have a performance engine. Not stock

 

[Ricko1966]

Im a fan of Edelbrock (AFB) as the fuel level is below the gasket line, they are easy to adjust things like metering rods and springs, and they typically run good right out of the box. That being said my Malibu which is carbureted had the notorious off idle stumble. Turns out it is very lean for a split moment when dumping the clutch. My research indicates that Edelbrock actually changed the design sometime in the 90s to try to conform with evolving EPA standards. The work around this is to drill a specific jet which is not removable. Once it’s drilled it’s drilled. So to answer your question I might say the older stuff may be better in some cases. YMMV

Do you have the accelerator pump rod in the position closest to the carb( most shot)

 

[K5Rob]

Do you have the accelerator pump rod in the position closest to the carb( most shot)

Yes I do

 

[Matt69olds]

Maybe I should have asked, if properly dialed in, are these modern carbs superior to the OEM ones? And if so, how?

But maybe the only time you'd ever notice is if you have a performance engine. Not stock

In my opinion, no. It’s hard to beat a well tuned Q-Jet. The Q-Jet is very sensitive, and versatile, but it takes someone with experience and patience to set it up right. You can’t take a Q-Jet calibrated for a 305 and bolt it on a rowdy 454 (or vice versa) and expect it to run well. The other problem: lots of wear. After 50 years of use, the throttle shaft bores are worn out, cause vacuum leaks around the throttle shafts. You are t going to fix that kind of wear with a 30 dollar autozone rebuild kit and a can of carb cleaner.

Which brings up the last Q-Jet “flaw”, people who have no clue how to take one apart and reassemble it correctly. It’s very common and easy to bend the power piston hangers, resulting in the metering rods not being the same level. That results in half the engine running with a different A/F ratio, no amount of tuning is going to fix that!! Or you get people that don’t install the float hanger right, and wonder why it floods.

The only way a Holley would be superior to a well tuned Q-jet is if the engine needs more airflow that a Q-Jet can provide. Considering every Q-Jet is capable of at least 750 cfm, that would need to be a pretty stout street engine.

 

[PhotonFanatic]

In my opinion, no. It’s hard to beat a well tuned Q-Jet. The Q-Jet is very sensitive, and versatile, but it takes someone with experience and patience to set it up right. You can’t take a Q-Jet calibrated for a 305 and bolt it on a rowdy 454 (or vice versa) and expect it to run well. The other problem: lots of wear. After 50 years of use, the throttle shaft bores are worn out, cause vacuum leaks around the throttle shafts. You are t going to fix that kind of wear with a 30 dollar autozone rebuild kit and a can of carb cleaner.

Which brings up the last Q-Jet “flaw”, people who have no clue how to take one apart and reassemble it correctly. It’s very common and easy to bend the power piston hangers, resulting in the metering rods not being the same level. That results in half the engine running with a different A/F ratio, no amount of tuning is going to fix that!! Or you get people that don’t install the float hanger right, and wonder why it floods.

The only way a Holley would be superior to a well tuned Q-jet is if the engine needs more airflow that a Q-Jet can provide. Considering every Q-Jet is capable of at least 750 cfm, that would need to be a pretty stout street engine.

Sounds like the aftermarket carb might be the better purchase, since people who have mastered the quadrajet are getting hard to find. There's probably way more info to be found on how to properly set up your edelbrock. Along with support from the company itself. And the brand new carb is new, not worn out so you wouldn't be trying to hunt down the less available parts.

 

[Ricko1966]

Sounds like the aftermarket carb might be the better purchase, since people who have mastered the quadrajet are getting hard to find. There's probably way more info to be found on how to properly set up your edelbrock. Along with support from the company itself. And the brand new carb is new, not worn out so you wouldn't be trying to hunt down the less available parts.

If your truck is stock or close to it there are several companies that do a good job of rebuilding them and making them right. Why are you asking all these intake questions. Are you planning something?

 

[Bextreme04]

Sounds like the aftermarket carb might be the better purchase, since people who have mastered the quadrajet are getting hard to find. There's probably way more info to be found on how to properly set up your edelbrock. Along with support from the company itself. And the brand new carb is new, not worn out so you wouldn't be trying to hunt down the less available parts.

Literally none of that is true. Quadrajet parts are readily available and support is prevalent. Edelbrock is simple and easy to get "good enough", but is far from reliable. They provide a simple adjustment sheet and thats about it. Don't expect much of anything from them in the way of "support". There were millions of quadrajets made for multiple decades. Do some research on what it would take to get your original carb rebuilt.

https://quadrajetparts.com/
https://quadrajetpower.com/
and https://cliffshighperformance.com/ are all great sources for all things quadrajet. Especially Cliffs, which has a solid forum and decades of happy customers.

 

[legopnuematic]

Or you get people that don’t install the float hanger right, and wonder why it floods.

I am not what I would consider a seasoned Q-jet builder, but I've been through about 5 of them and most recently I rebuilt (full rebuild, bushed the throttle shaft and well plug reseal) the original one from my 76 and managed to do that.

They chose a very convenient place to put holes to not use to put the float hanger in.

I do it right cause I do it twice...

 

[TotalyHucked]

Y'all know I'm not a carb guy whatsoever but I've driven enough of them that I'd go through hell and back to have a good quadrajet on whatever I was driving over any other carb. They're just so good when they're right

 

[Matt69olds]

I am not what I would consider a seasoned Q-jet builder, but I've been through about 5 of them and most recently I rebuilt (full rebuild, bushed the throttle shaft and well plug reseal) the original one from my 76 and managed to do that.

They chose a very convenient place to put holes to not use to put the float hanger in.

I do it right cause I do it twice...

Yep, I have taken apart lots of cores with the float hanger clip in the wrong place. Or the metering rod hangers mangled.

20 years ago, I could almost understand how mistakes like that could be made. Now, reassemble instructions AND video is no further than YouTube.

I’m pretty comfortable building Q-Jets, but if it’s a non stock application, I get with a specialist. They have the experience and the knowledge to suggest a carb recipe that will get the calibration in the ballpark.

 

[PhotonFanatic]

If your truck is stock or close to it there are several companies that do a good job of rebuilding them and making them right. Why are you asking all these intake questions. Are you planning something?

I bought a 70's truck to fix up, and I figured it would be nice to have the best possible fuel system. It didn't come with a carb, and I know some people like to tune their own carbs and I thought "Hey! That could be me"!

Most of my previous experience with carbs has been negative, but this was all when I was much younger. I've since learned a lot so I thought maybe these newer carbs might yield some kind of default better experience.

 

[xm20k]

Downside with the Q jet is the number of people that don't know how to work on and or tune them who screw them up and then sell them used on ebay/marketplace etc. missing parts and all other manner of who knows what done to them if you buy a new repop one they are all chineseum and most likely not spec or instead of a correct alloy they are straight aluminum and they corrode and malfunction within a matter of months. There may be a reproducer out there that is worth using but I don't know of one off hand.

Unless you can find a rebuilder that knows what they are doing who uses old cores you'd be better off buying an Edelbrock AVS2 or similar for a street driven vehicle.