By all means, keep it if plans for a 100% NCRS restoration are in the future.

But Ignore sound advice at your peril, the facts are these:

The Q junk isn’t made anymore. Hasn’t been made for years. Junk yards are full of them. Parts are nearly impossible to find, and builders who know anything about them even harder to find. There are few clones or aftermarket parts available.

Why is that? Because they are so efficient? Maybe it’s because they win so many races. Could it be that they are user friendly and actually do what they were designed to do? Or…..could it be that they SUCK?????

Heaven forbid if anything ever happened to the Wonderful Wizard of Q, Lars. There are guys on this forum who will never get their junk working again.

Factoid: If you drive like a milk toast with the hot, lean running small bore Q you may enjoy slightly better gas mileage. If, however, you like to get on it a bit, maybe hit a stop light once in while, dodge the cars on the freeway, or just impress the grand kids in a parking lot, a 600 Holley square bore will give you as good gas mileage, better response and more even acceleration.

Factoid: A bigger CFM does not translate to better performance. The only reason Q junks are capable of 750 CFM is because they were designed for all GM vehicles. The vast majority of motors do not need any 750 cfm carb. All it does is waste fuel and send fumes out the tailpipe.

In a Q junk, flow is controlled by a system of rods and jets that allow the motor to get as much as it needs to run. Hence, it is often called an, “on-demand” system. What it really means is that for each application it is meant to run as eco friendly, hot and lean as possible without damage to the motor. “Setting Up” a junk is merely the right combination of rods, jets and tweaking for your application.

Generally, you enrichen the mixture a little bit your car will run better. This can be done by swapping out parts and some machining, or machining existing parts. Some backyard guys use files and reamers to do this.

Or, you can buy a 600 CFM Holley that is already set up. Holley is still being developed and improved upon. Parts and accessories are available everywhere. You don’t need to be a machinist or rocket scientist to set it up. Edelbrock is the same way! Edelbrock carbs are mostly clones of the original Carter (not the Q Carter).

If your car smells of gas and fumes are coming out the back, it is probably because you have too big a carb for you motor. In the case of a Q junk, one that isn’t “set up” right.

 

Actually, I am not quite sure what a factoid is, but my post was for the OP.

 

Will a 600 holley fit under the stock dual snorkel air filter housing with out modifications to the filter housing?

 

I generally don't like qjet's for the following reasons:

1. They are overly complicated to do a relatively simple job
2. They provide decent mileage and power if you can get them to run correctly.
3. They are difficult to tune and rebuilt correctly
4. The Qjet was GM's attempt at precisely metering fuel through a carb instead of running true mechanical fuel injection like most foreign sports car manufacturers were doing in the late 70's, early 80's.

Personally, I have run a Holley 4175 650 CFM vacuum secondary Qjet replacement since 1985 and it has performed perfectly. I rebuilt it in 2010 and the rebuild was easy. Very easy to custom tune as well and the gas mileage is within 1 MPG of the OEM Qjet-insignificant!

Just my thoughts!

 

#1 on Q-Jet.

 

I agree with your poignant and well thought out post.

The rest was generated by the smarmy comment above yours.

 

And your (factless) comment about the Q-Jet wasn't "smarmy"???

 

My QJUNK 750cfm running 7.8 seconds on 1/8th. Wish I had a video of my Holley 750 running 8.1 seconds on that same track.

 

Some guys just can't face the facts. Mine are correct. You....err...well you don't have any.

oh, and the word is smarmy, not swarmy. Get your vocabulary right.

smarm·y
/ˈsmärmē/Adjective
Ingratiating and wheedling in a way that is perceived as insincere or excessive; unctuous.

 

People are afraid of the things they don't understand, and it's quite apparent that you don't understand how a Q-jet works.

 

Someone always jumps in with an "exception" to the norm.

I doubt that a carb swap, with no other changes, modifications or tuning would make that difference. .3 of a second? c'mon now.

One pass means nothing.

What was done to the Q, what was done to the Holley?

What tuning and engine differences?

What would happen if you put on a Demon, or a Quick Fuel an Edelbrock or Carter?

The FACT is, Q Jet is the least used carb in racing for a number of reasons.

The number 1 race carb for serious competition is a Holley, then Demon.

For street fighters, the most commonly used carbs are Holly, Edelbrock and Carter, in that order.

Guys, there is REASON for this. Their overall performance is better.

 

* Availability of parts
* Ease of tuning - primary jet changes on QJets are not trivial.
* Access to more intake manifolds

Numerous dynotests have shown QJets to match Holleys on HP and beat them on low end torque.

When you're dealing with a strip-only car, who cares about street driving characteristics? The QuadraJet is all about that; for a car that lives its life with Vin Diesel, the advantages of the Holley modular carb system easily outweigh the advantages of the QuadraJets.

The "race on Sunday sell on Monday" philosophy applies quite well here too; they have a good market because the big boys are using them.

If I were building a car that got towed to and from the track, I'd build a Holley. If I were building a car I drove around town and occasionally took to the track, I'd stick with the M4Ms in my garage.

(and I'd never pick an Edelbrock/Carter over a QJ or Holley, lol)

 

Actually it's quite the opposite. I'm very familiar with them. And can restore them, but won't.

Then I read all the comments about how great they are end with:

"CALL LARS"

They don't have a clue.

 

If the OP just got the 76 and wants to get it running to sort out what he has, rebuilding the Q-Jet is the fastest, easiest way to a running car. He wouldn't have to worry about linkage, vacuum lines, air cleaner, etc.. Lars' prices are very reasonable and by the way, I believe he also does Holley's. If you look for his last post about superchargers, there is a Demon carb on the engine he's playing with.

One excellent reason to send a carb out that has been sitting around for awhile is the quality of cleaning fluids that is allowed in that particular state or area. Without a good cleaning to clear out passages, that carb is doomed to failure. A professional (not commercial) rebuilder will also pick up on nasty things done by previous owners/mechanic (BUBBA).
Just my opinion

 

A well thought out comment.

The Q may have a small, albeit tiny, advantage in the low rpm range. A typical Holley does prefer to run a bit faster.

I disagree when you start to get off idle. That is when the Holley really turns on. And contrary to common belief, that "kick in the seat" feel from a q junk is when the two big ones come online.

That is not a desireable characteristic. And in fact, for a second or two starves your motor and causes it to slow down.

The Holley with all four barrels in sync pulls through the entire band more smoothly and with constant power.

This is true whether you are at the track or merging onto the freeway.

I am always reminded of what the old guys used to say to me at the track when I was a young guy, "A volkswagon has great low end torque and will beat a vette off the line for the first inch".

I have always said that if driving the eco friendly stocker is your cup of tea, the q will work just fine.....until it doesn't.

It seems to me the OP should be aware of the options and not just fall in with the "call Lars" crowd.

What is amazing to me is all these guys who are willing to spend thousands on a numbers correct q for their cars. An early 70's 454, for example, is rare. And commands a lot of money for the restorer, collector.

Problem is, it is the same carb that GM put in trucks. And the body is the same as a million other q's.

Now, don't get me wrong, my specialty is old Harleys. And I have been known over the years to spend absurd amounts of coin on "authentic" parts that you can get at Lowes. And kick myself the entire time.

So, while I don't agree to restoring a q junk, I can understand it.

 

My carb does not have a "kick in the seat" feel from engaging the secondaries - this is endemic of the secondary valves opening too quickly, usually from the air valve tension being too loose (shade tree hot rod trick, or just a worn 30 year old spring), or from the choke pull-off being blown or releasing too quickly. With these problems sorted, you don't have that 1-2 second gap which I'll agree with you as a very real number.

Another problem is that the bulk of them are calibrated quite lean from the factory, to the point that the secondary transition will cause a bog. No accelerator pump shot can safely make the gap that some of these quads have after being lean burn to start with, and then throwing ethanol blended gas into the mix. All of this can be fixed through experimentation.

It's sort of the opposite problem of a Holley; these were designed to run quite rich so no one's motor would burn up with an off the shelf calibration. You won't find a lot of dynosheet power by tuning them, but you will find throttle response and fuel economy. GM had the benefit of being able to tune unique castings for unique powertrain packages, and the handicap of having to have these cars pass smog. Engines that were never designed for it. Run 'em lean, throw a cat on and add ten other garbage systems to handle edge cases. Bleh. And 30 years later people are running stock calibration QuadraJets with gas that burns even leaner. It's no wonder they run like complete crap. Probably with worn out secondary cams and springs. A worn out secondary cam will limit the amount of fuel delivery to the secondary circuit (rods won't pull out as quick) and the spring, as mentioned before, will cause that lovely QuadraBog.

All of that said, I probably spent about 10 hours learning how to do my first QJet. Had it on and off the car 5 times or so playing with jets, rods, float levels and running it down the road. It now runs quite well and is more efficient than ever.

I would have had less time into a Holley for sure, but living in CA I'd have to go back to the QJ once every 2 years. Not to mention the headache of re-plumbing for those. Too much of a perfectionist to just run a rubber fuel line from pump to carb and snake it around for different carb setups. I also don't like engine fires.

 

commander47...

I think everyone understands your M.O. by now. So we can just ignore you from now on.

 

Is it me that I feel so much hostility from Commander for Lars and Qjet?
Is he getting paid from Holley to hate on qjets? Or did Lars steal his GF or something?

One thing I know for sure is that I would never have a JUNK pouring fuel down my intake for my ridiculously expensive engine.

 

Posts like this just qwack me up...

Commando and I have nothing against each other... He likes Holleys, and I happen to be pretty good at setting up a Q-Jet (and I do a pretty good job on all the Holleys I do, too). Him and I would probably be a pretty good entertainment act at a bar serving good Bourbon, and we'd have a heckuva' good time doing it. Commando gets good entertainment out of a running post like this... And I just drink my Martini and laugh about the thought of having a drink with this guy... This is too much fun..

Lars

 

Does this mean your cooking up another project like the supercharger?