Quadrajet Selection

[oldschoolss]

Hello Guys,

I have a 1962 327 that I want to put a quadrajet on along with vortec heads. I have a couple quadrajets laying on the shelf, I think two are off 75 or 76 BOP applications. Both have the heat riser choke but they also have a terminal coming off them... Anyways I took the one that's a 800 cfm unit to a friend to help me rebuild it. He told me not to use it as all the 75 and later carbs as they are not good as they are very picky and have lots of drivability issues.

Is this true? I was thinking of rebuilding the 750 CFM unit for my 327. I can pull the actual number tonight, I'm pretty sure it was a 75 model.

Thanks,

Scott

[Cliff Ruggles]

Scott, the later carburetors made in and after 1976 with the later style APT feature are actually superior to all previous designs in every area.

They are just a tad lean as they were produced under tighter emission standards than the older models.  If you plan on using one of them outside of it's original application (obviously), get one of our books and use the rebuilding chapter for complete/correct rebuilding, and the high performance chapter to recalibrate it exactly for the application.

We sell complete/correct rebuild/tuning kits for the later units.

BTW, I use a 1977 Pontiac carburetor (part number 17057274) on my 455 engine that powers my 1973 Ventura.  The car runs low 11's in full street trim on DOT tires.  We dyno and track tested the carburetor against a Demon 850, Holley HP 950 and a Holley 850 DP carburetor.  The Quadrajet made more power on the dyno and outran the other brands on back to back testing at the dragstrip.  Although the magazines did not cover all the test results, some of the information made it into High Performance Pontiac and Popular Hot Rodding's Engine Masters edition a few years ago.

The Quadrajet we used was not ported or altered in any way by grinding or sanding, bead blasting, etc.  It was an as cast unit with upgraded tuning parts, completely blueprinted/recalibrated with performance modifications as outlined in our book......Cliff

[jxu109]

Too bad there isn't more data in the magazines on Qjets vs Aftermarket carbs, but I suppose that would really upset the advertisers of the magazines.

[Cliff Ruggles]

It's all about politics.  We have found over the years that you are allowed to compete with aftermarket parts, but not allowed to outrun them. 

Consider this.  Magazines catering to the high performance industry are filled from front to rear with advertisements, telling us how much better all the shiney parts are when installed on our older vehicles.  They pay for considerable advertisement space.  Any articles found in those magazines are not going to typically show that stock parts outrun the "high performance" parts.

Speaking specifially about the quadrajet, they are excellent for high performance use.   Two things have been working against them for years.  Very early units were HORRIBLE, leaking bottom plugs, POS fuel inlet valve assemblies, poor float hinge pin location, etc.

They quickly gave the Quadrajet it's "Quadrajunk" reputation, even though the factory corrected these issues by 1969.  At that time, fuel was cheap, so EVERYONE dumped the factory carburetors and bought a Holley 600 vacuum secondary carb, often a $75 Edelbrock intake to go with it.  Neither one of those parts made any more power than the stock ones, but you could at least put the Holley sticker in your window, have everyones eyes burning who got anywhere near the rear of your car, and do "donuts" in the  High School parking lot!

Even though a few of us figured out that the Quadrajets were excellent, the early 70's brought on very tight emission standards, and the carburetors we had access to were HORRIBLE, being so lean at idle/off idle they wouldn't work well on any "high performance" engine.

The bad reputation continued, and is still around these days, handed down over the generations, tyically from folks who's cars are held together with super glue and rubber bands, and no faster than a Dodge Neon with a plug wire or two pulled off!

Just making some humor here, but there is some truth between the lines.  When we race our car at local tracks, folks always come over to see what's lurking under the hood to make such a quiet daily driver so fast.  When they see the quadrajet, the look you get.....PRICELESS!

These days we don't hear nearly as much of the "quadrajunk" comments, especially when we are in final rounds at big races, running faster with our stock parts than folks with all the latest "bling"!.......Cliff

[jxu109]

I've had plenty of people tell me that I can make make my qjet run pretty well (as if I didn't already know that), but if I want the best performance, I'll need to switch to a Holley or Edelbrock.

Sometimes I start an argument, other times I laugh and move on.   

[Cliff Ruggles]

Here's some cold hard facts, from dyno sessions we've made with engines prepared here, and track runs that followed.

The old 455 that powered my car produced 494hp and 514hp on the dyno with a recalibrated 1977 Pontiac q-jet on two seperate occassions, one of which was for a magazine article that made it into High Performance Pontiac and Popular Hot Roddings "Engine Masters" addition.  Several aftermarket carburetors (850 cfm DP carbs) were bolted on behind the q-jet on each occassion, and cranked out LESS power, apprx 2hp and 3-4 ft lbs torque. (back to back pulls)

Keep in mind here, that the q-jet was box stock (no sanding, grinding, knocking out casting flash, or porting in any way), only recalibrated exactly for the application.

We followed up the dyno testing by installing the engine back in the car and making track runs with it.  It ran EXACTLY .02 seconds and .30mph FASTER with the q-jet than the "big" 850 DP carburetor.

We've done the "back to back" swap with other aftermarket "high performance" carburetors, and in each and every case, they made less power and ran slower a the track than our plain old 1977 Pontiac Q-jet.

This testing included the Edelbrock 750 cfm "Performer" series carburetors, and the new "Thunder" series 800cfm units.

The most interesting part of some of this testing, was that it was witnessed, and actually asked for by representatives from magazines so they could write aritcles from the information.  Since we outran the aftermarket stuff, you will not see any of the test results in print, wonder why?......Cliff

[omaha]

I agree with ya Cliff. It's hard to convince someone that a carb that you paid $20 for at the swap meet could actually outdo the carb that a person paid $300-$500 or more for. Sure you gotta add the cost for rebuilding, but even then it still is an incredible deal. All you have to add is the knowledge. That is what makes all the difference!   [btw; Cliff's book has the "knowledge"].

[Cliff Ruggles]

I'm actually surprised that some of these aftermarket companies haven't put a contract out on me.  I've caused the demise of quite a few "high performance" carburetors over the years!

The other item that needs mentioned here are the intake manifolds.  Many of the factory intakes, even EGR versions, are excellent.  Aside from the weight, no negatives from using them, even for racing.

Right on the dyno, my slightly modded 1970 Pontiac cast iron intake, made 7 more HP than an Edelbrock RPM.  The Performer intake wouldn't even feed the 497hp engine we were testing.

At the track, I've tested the Torker, Street Dominator, Performer, and the Tomahawk intakes.  My iron intake ran .02 seconds faster than all of them.  The next best intake was the Tomahawk, with a 1" spacer.  It ran 2mph faster, but still slower in ET, showing how much low and mid-range power is lost when switching to a single plane intake.  At that time, my engine (455) was making right at 514hp/587tq, and the car was running mid-11's.  Imagine how much power one gives up on a smaller engine making less power?.....Cliff

[omaha]

I never knew that [about the fact. intakes]. I'll keep the fact. iron on my 350 pontiac then!