I was wondering if anyone has done a test between the two at the track.When doing a search people are turning 11's with quad. and with holley's. I,ve used both but i'm not very good at tuning a quadrajet maybe that's why I stay away from them.My uncle runs a 800 cfm quad. on his nova and we were wanting to put on my holley double pump and try it but we never made it back to the track.So everyone give me your results,it's cold out and I have to much time to think! smile.gif

I myself havent ran a Qjet at the track, but a freind of mine who was great with them. Did some testing and found the Holleys worked much better. Qjets can work great as the boys in SS classes have shown. But they spend real big bucks on their engines. For the typicall Car enthusist Holley is the better choice

My times aren't that good (mid to high 13's) but the trap speed is what showed a diff....
With the quadrajet I couldn't get it past 101 or 102 most of the time but since I've installed a holley spreadbore I can usaully get up in the 103 -104 range. Easier to tune but you have to do it more often and because the rochester is not easy to tune it was probably never really daled in on my car.
Just an FYI I loved the rochester I got 17 miles to the gallon on the highway an the holley usually does around 15 and the performance is not something I could feel seat of the pants. The only reason I got rid of the rochester was because I couldn't find a part that broke abd the holley was 50 bucks...and also so I could experiment..

Originally posted by BLK64SS:
I myself havent ran a Qjet at the track, but a freind of mine who was great with them. Did some testing and found the Holleys worked much better. Qjets can work great as the boys in SS classes have shown. But they spend real big bucks on their engines. For the typicall Car enthusist Holley is the better choice How about the guys who run Holleys on their SS cars? Do they spend big bucks, too?
I have about $16 invested in my Q-jet, freeing up a few hundred dineros that I could invest in a converter. The car is a daily driver that runs 11.70's @ 117 mph and gets 18 mpg on the road. Jim Hand did some testing with a Pro Systems 830 cfm Holley and a homemade 750 Q-jet and found that the Holley was worth about a tenth on his setup.

Yes of course they spend the same money. I guess I Worded that wrong. The only point I was tryin to make is that for performance the Holley is the better choice. Maybe I should've just said that.I have never had good luck with Holleys that came from someones shop " modified " I dont have anything against the Quads, I do perfer them over Holleys for daily drivers. But if performance is the goal .. then Holley is the choice thats just my 2 cents worth. Oneofakind.. do you happen to have a bottle on that also ?
Duane

No bottle, no tach, no traction bars, no hood scoop, column shifter, trailer hitch, stock valve covers, full 2-1/2" quiet exhaust system, mild 224° cam. We've had several requests to look in the trunk for a bottle, but there's nothing in there but a spare tire, jack and a toolbox. The tranny shifts itself at 5500 and we lock the converter as soon as we get in third gear. This car is a daily driver that runs 11's, not an 11-second car that's used as a daily driver.

The car gains 25 mph in the last eighth, from 7.50@92 to 11.75@117, so I expect that we can run some 11.50's or so if we spend a little time on the chassis. I recently swapped the drivetrain over to a 66 Nova sedan with a roll bar in it and I bought a set of Tri-City Launchers from Chuck Rayburn's B/SA Dodge. We revamped the exhaust system to include some 1-5/8" x 40" primary tubes with a 2-1/2" merge collector. I'm also looking at using a 2004R instead of the 700R4.

http://www.autoimagery.com/rayburn.htm

Oneofakind.. Sounds like you hit a real good combo ! I'm impressed with it. The guy I know who does the Qjets had a similar combo in a '70 wagon. Just a real mild 355 that ran 11.90's at a high altitude track yet he could and did drive it everywhere every day. It was a project car that he and a guy from AFR did years ago.
Good Luck with it !
Duane

My ElCamino G/SA car goes 11.4's all day.It has a 7029202 4MV Rochester and a cast iron 3927184 manifold.The car weighs 3470 with driver(class min)and a 9in tire.Yes you can make a Rochester work as well as a Holley and spend the money you saved on making the chassis work!Just take your time finding a good one(no cracks,warped air horn,or worn out throttle shafts).Secondary metering rods and cams are dime a dozen from your local junk yard,my guy is happy I take the steel out of the aluminum housings,that the parts are free.You can experiment with a die grinder by retapering the step in the secondary rods or the ramp on the cam until you find the right combo for your set up.Changing mertering rods is much easier on a Rochester than jets or vacuum secondary springs on a Holley.I have seen some pretty unbelievable flow numbers from 4ME's,one in excess of 950 cfm's,I didnt believe it until I saw it on the flowbench!!!Good Luck and remember this is supposed to be FUN!!!!!!!! graemlins/thumbsup.gif

The Q-Jet is the great carb that STILL gets no respect. Puzzling really, especially considering how much research and development GM put into the Q-Jet. The only thing that comes to mind is how cheaply Holleys were available from all the speed shops during the musclecar years, vs how expensive Q-Jets were - which mostly had to be bought through higher markup dealership parts depts. Rochester never went after the performance carb market the way Holley did.

Interesting to note that most of the racers I see who have figured out the Q-Jet are running Pontiacs. In the March '04 issue of High Performance Pontiac there is a '66 GTO raced by a retired lady school principal. Her 462 cube Pontiac has laid down a n/a best of 10.23 e.t. at 129 mph. Perched on top of the engine is a Q-Jet. As mentioned above, Jim Hand is another racer getting results from the Q-Jet.

Thomas

Originally posted by 69G/SA:
My ElCamino G/SA car goes 11.4's all day.It has a 7029202 4MV Rochester and a cast iron 3927184 manifold.The car weighs 3470 with driver(class min)and a 9in tire.Yes you can make a Rochester work as well as a Holley and spend the money you saved on making the chassis work!Just take your time finding a good one(no cracks,warped air horn,or worn out throttle shafts).Secondary metering rods and cams are dime a dozen from your local junk yard,my guy is happy I take the steel out of the aluminum housings,that the parts are free.You can experiment with a die grinder by retapering the step in the secondary rods or the ramp on the cam until you find the right combo for your set up.Changing mertering rods is much easier on a Rochester than jets or vacuum secondary springs on a Holley.I have seen some pretty unbelievable flow numbers from 4ME's,one in excess of 950 cfm's,I didnt believe it until I saw it on the flowbench!!!Good Luck and remember this is supposed to be FUN!!!!!!!! graemlins/thumbsup.gif :eek: WOW! Thats pretty cool! I was debating about eventually replacing my manifold, a 3927184 manifold with a Performer or something, but after seeing your post, I dont know tongue.gif . Did you modify it somehow? Are you running a 383 or something? What is the rest of your combo, If I may ask smile.gif ?

I used to be a Qjet naysayer, but I like it now (I still like Holleys, too). I finally got a good one, and that makes all the difference in the world. I wish I could find me a "freebie" junkyard for Qjet parts (freebie LEGITAMATELY of course ;) ).

Originally posted by 69G/SA:
My ElCamino G/SA car goes 11.4's all day.It has a 7029202 4MV Rochester and a cast iron 3927184 manifold.... I have to ask, did you make any mods on the intake? When I switched back to the GM "3919803" 1968 Qj intake from the Ebrock Performer, I seemed to have lost a hair of performance.

Buzz,

you have mail.

Mike

To run as a NHRA stock car, you must run a stock intake manifold, stock heads, stock-type pistons and a stock-type carburetor and a stock lift cam. There is a list of casting numbers legal for each engine combination. This wouldn't be a stroker motor, they are allowed about .015" leeway in the stroke. It's amazing how quick these guys can make a rather plain 350" motor run.

Hi,
Oneofakind is right about how stock my engine is,I have not modified the manifold or heads in any way except for a legal valve job.The trick is finding good castings they are not equal.I have seen one manifold with so much casting flash I'd swear the car had to have a miss!!I use JE pistons, Speed Pro rings,Oliver rods ,ARP bolts,Clevite77 bearings,single springs with a damper and 10 degree locks,stamped rockers with a MSD 7AL and billet dist.We are also limited to .410 lift cam.The car has a TH350 with a Coan converter that stalls around 4800 rpm and a 12 bolt on 9.0x29.5x15 M+H slicks.The car has a flat hood and I use a stock 300hp air cleaner assembly that I opened up on the bottom with a K+N filter.I aslo drive the alternator and water pump off the crank and have a mechanical fuel pump.I spent alot of money on fully adjustable STAHL headers and they were worth it!Also it has a cast crank and a 2 bolt block.I'm sorry if I'm a little vague on some of the specs but after all this is a competition car and I race for money not just the points!HA HA.Feel free to email me about specific issues,I'd be glad to help if I can.
Peace,
Steve

What do you guys run for an intake manifold with these Qjet's. I have a LS5 manifold I am wanting to run.

My friend did a test with his 77 455 Grand Prix @Atco back in 1988.
850 holley ran 13.33 avg
Qjet ran 13.20's avg this was a yard Qjet .073primarys w/.035 sec rod and the choke pull off hole opened up.

Originally posted by onovakind67:
I have about $16 invested in my Q-jet, freeing up a few hundred dineros that I could invest in a converter. The car is a daily driver that runs 11.70's @ 117 mph and gets 18 mpg on the road. Jim Hand did some testing with a Pro Systems 830 cfm Holley and a homemade 750 Q-jet and found that the Holley was worth about a tenth on his setup. What kinda heads do you have on your car? Did you do anything special to them? What are the gear ratios in a 700R4? What kinda gears do you have in the rear? Was the 11.70 pass with slicks? What was yur 60'? Just curious ;)

It's a standard 700R4 - 3.06, 1.6?, 1.00 and .7. I have 4.10 gears and 26x9" Hoosier slicks. The heads are old SportsmanII's with the valve pockets opened up. The 60' times are about 1.65, 1/8th is 7.50 @ 92.

a hot rod buddy here was running consistent 7.70's on our 1/8th in a HEAVY 455 GS with a stock QJet.... I'm just to ignorant (or to lazy to learn how) to tune one...

I think that a vac secondary Holley and a Q-jet of the same CFM will perform exactly the same ET wise in the 1/4 if they are both set up properly.

The problem with the Q-Jet is that very few people know how to set one up properly (myself included) and the aftermarket support just isn't there like the Holley.

Then there are manifolds to consider . . . how many high performance spread bore manifolds are out there?

It's pretty easy to adapt the carb to any manifold.

For bbc's, the ugly GM marine casting has dual flange, but its rectal. CHeap though. Might have to splurge on a Performer QJ oval port mani.

I'm surprised no one is illuding to it, but I suspect the same thing that makes a Q'Jet great on the street is the same thing that makes it sub-par in racing.

Before reading this, learn how the venturi in a carb works!! That will explain it all.

Now the Q'Jet has been famous for it's small primary (awesome street manners) ... and then a HUGE secondary (everyone like to hear them roar). That large secondary decrease the repeatability of the vacuum signal going to the fuel bowl (compared to a smaller one), so it becomes slightly eraditic ... at a very minute level.

Now don't read too much into this ... I have always used Q'Jets and still think they are the best carb that was made, even in drag racing! There's a lot of design features going on in the secondaries on a Q'Jet, that can't be adjusted with a Holley.

After saying this ... anybody want to get brave, and try to DECREASE the secondary on a Q'Jet? Truth is, very few SBC need the 800cfm going through there.

What do you all think?
Neal

The secondary venturi in a Q-jet is established by the shape of the air valve and the inner plate. As the air valve opens, the venturi changes size to match the airflow, as well as increasing the fuel flow. If sufficient flow isn't created, the venturi never gets larger. Decreasing the secondary throttle bore would have little effect except to limit the flow if the air valve was to open that wide. Some factory Q-jets have a limited secondary opening. The main difference between the 750 and 800 cfm GM Q-jets is in the primary venturi diameter.

Man, now I'm posting this without a carb in front of me ... correct me if I'm wrong, but please listen.

I don't think you want to confuse the air valve with a venturi. The air valve is limiting the max air cfm going in so that it doesn't overload the engine ... great feature on Q'Jets and made them usable on almost anything.

A venturi is an hourglass looking shape. The fuel bleed ports will work on the vacuum signal from these. A smaller venturi will increase the vacuum response signal.

All carburators work on this vacuum signal going to the fuel bowl. A good example, is the idle fuel bleed common to Q'Jets. The primary has a triple-venturi design that requires next to no vacuum to start sucking fuel.

Again, like I said there are other design features in the secondaries that make it an apples to oranges compared to a Holley ... but the air valve is not intented to be a venturi for the fuel bowls.

Thanks, Neal

If you look down the secondaries of a Q-jet with air valves removed, you will notice that there is no venturi, only a reasonably circular hole leading directly to the throttle plates. The throttle plate is actually the smallest point in the bore. About 1/3 of the way from the leading edge is a baffle, over which the fuel discharge tubes are positioned.
If you take a side view of the air valve plates, you will notice that they are s-shaped. The air valve(s) pivot so the rear of the air valve comes down to the rear of the baffle, creating a venturi and a low pressure area between the valve and the baffle. This attracts the fuel out of the tubes, modulated by the secondary control rods. Here's a link to Edelbrock's manual with a reasonable picture:

http://www.florida4x4.com/tech/quadrajet/1910_OwnersManual.pdf