Best quadrajet?

What is the best quadrajet and why? I plan to rebuild one, or give it a good college try, and before I put considerable time and effort into it I would like to know what the group thinks.

Thanks,

Scott

 

If you are thinking performance, go with a #7042240 Q-Jet. It is a big block carb from 1972 and has an 800 cfm rating. (I assume you are running a 400/430/455 etc.)

John

 

I actually have a 350, but heard that the 455 quadrajet was pretty much bolt on performance due to difference in jetting and larger cfm. And leads on where I might get one cheaply?

Thanks

Scott

 

Therein lies the problem! They show up here and on ebay, but decent cores run upward of $35+. And by now, most of what's out there on the low price end has been butchered to some extent for parts.

I think it's in Doug Roe's book that I read the suggestion that keeping the carb that came with the motor is most practical.

And then there's the performance upgrades that are part matching parts of a total "package" involving owner's expectations and all aspects of the driveline (engine, cam, carb, trans, gears, etc.). That's where the Greg Gesslers and Cliff Ruggles earn ther stripes!

 

Stick with a 750 Q jet. I has the correct idle circuit for your engine and it will deliver all you need for a near stock 350. Even a 70 455 Q jet is a 750.

 

Scott,

If it is a 350, I would stick with a carb for a 350 engine and tune it to what you need. I have heard, that using a big block carb on a small block can lead to problemso No:

If you need some help, talk to Cliff Ruggles, or Greg Gessler, I believe they both belong to this board. Good luck.

John

 

Who is really the foremost authorities here on V8Buick to rebuild QJ's? I've always wanted to know this and perhaps it would help this gentleman as well.

 

"Check out our website at cliffshighperformance.com, there is a Forum there where you can sign up and post questions, problems, ask for advice, etc.

We offer many services in addition to complete/correct rebuilding, performance mods, custom tuning, etc.

These include complete rebuilding of throttle bodies with bronze bushings, heli-coil installation for the 7/8-20 threads (carburetors up thru 1971), and installation of screw in bottom plugs for leaky factory pressed in plugs.

We can also zinc/chromate castings (not copy cad, dipped in iodine or painted).

We have many hard to find parts as well, thanks for checking us out.

I also have several Buick hard to find cores, including one 1971 GS 7041246 casting.....thanks....Cliff"

 

Can you give me an idea on the cost of a complete rebuild and refinish on a 72 350 Quad. The rebuild I had done not to long ago does just not seem right. Shipped to and from central Florida.

 

You need to contact Cliff at the email address above.

 

I just shipped a carb to Cliff today. Beware his backlog is 5-6 months. I sent mine anyway as it's winter and it'll be back right around the time the cars get pulled out up here in Ct.

As Jim Lore said, send Cliff an email. He responds quickly and is very accomodating to questions.

 

I vote for a 77-81 Q jet from a Buick 350. These have adjustable part throttle mixture and can be fine tuned very well without modifications.

 

I've found that a bone stock 71-74 455 carb (800 cfm) works great on a 350. It's a tad richer all the way thru which makes it better running on the 350 than 455 it was made for. Remember all these carbs were quite lean to begin with for emissions. The idle mixture is then actually adjustable. On the 455 it was never rich enough.....even all the way out.
On the 350 w/800 a slightly tighter air valve setting does the trick.

 

There is a chapter in our book about carburetor selection, and we cover the good and bad points.

Basically, the "best" q-jets would be any later model carburetor from 1976 and up with the later APT system. All front inlet models (non computer controlled) will be the larger castings.

The Buick 455 carbs from 71-74 top the list for divorced choke units.

The 73 and 74 Pontiac Super Duty carbs are also the large castings, and the only early design large cfm carbs than will accept an electric choke.

Rare but on the list are also the 1971 Pontiac "HO" carburetors, and the 1971 400 4 speed carb, part number 7041263. All of those units are missing the outer booster ring in the primary bores and are large cfms.

At the bottom of the list are any 65-67 unit that originally used the hopeless plunger inlet valve deal.

Next to the bottom are any 1967-68 units that used the early hinge pin location and large float, this includes Olds and Cadillac units to 1974. These can be made to work for high HP applications, but they aren't nearly as good as later designs with the revised hinge pin location and smaller floats.

That just about covers it, best news is that the very best q-jets are the ones most folks toss to the side in search of the holy grail stuff.

I use a 1977 Pontiac q-jet on my 600hp 455, originally from a 350 engine.

It's never had a grinder or sanding roll touch it, and has outran every Holley or Holley clone we're ran against it, dyno and at the track. We even did some back to back testing several years ago for a magazine article, and outran a well prepared 850 Holley. We went on and carried both carbs to the track and the q-jet went quicker in ET and faster in MPH.....not much of that testing made it into print....wonder why?:TU: .....Cliff

PS: left photo is a 1971 Pontiac q-jet 7041263, the right photo is the same part number I use on my own engine, 17057274.

 

350 or 455 carb, -- won't matter. Once it's modified the results are the same.

Modified 750 or 800 -- will still be 750/800 but will run like hell, with little, if any difference.

 

Oh by the way,
Modifications used to be .076 jets and .046 metering rods, set the air valve, timing of vac diaphram, and a few other things. The price was more than just a few dollars though.
With over jetted carbs we found better performance with 38 or more degrees of timing and destroyed a lot of engines.
Mine runs better with .073-.074 jets and 32 degrees timing than it ever did before and the recipe mods improved everything from idle to WOT.

Cliff Ruggles book has set the standards on Q-jet mods.
You can do a full recipe & change way more than we used to pay big $ for, and you should sure as hell get your moneys worth now.

I did a complete 2nd recipe from Cliff's book, unwarped my carb, reduced the jetting, reduced the timming, and WHAT A DIRFFERENCE. I even get better mileage.

 

Yes, I have a carb from Mr. Osborne in the same way.... It works great in all rpm ranges from idle to 6000 rpm as varified by wide band air/fuel ratio meters.

 

I got my quadrajet off of 69 430 and put it on my 350.I just did a standard rebuild and it works great.Helped my car go from 16's to a 13.07 at 104 in 1/4 mile.I been wondering about seeing if there is anything else I could do to get a little more out of it.

 

The "big" jets in the 71-74 Buick carbs was done to help with a part throttle lean condition more than anything else, as most use pretty big metering rods in them.

With this new fuel we typically will run .074" jets in them, and .044" metering rods and free up the APT in the baseplate to fine tune the part throttle A/F once the carb is placed in service.

We've got scores of those carbs out their in a wide variety of applications. They are a very good choice for anyone who wants a large cfm divorced choke carburetor. We like them for drag racing, and FAST class racing as well, when/where a divorced carburetor is needed.....Cliff