intake manifold/carb
09-19-2012, 05:34 PM
#22
Race Director
The point not taken here is the Qjet will power a 180 HP L48 up to a 500+hp big block with minor tuning changes and give excellent street performance, fuel mileage and likely better throttle response. Probably won't give anything up on the ET slip either. Holleys are easier to fine tune at the track and parts availability is better. If nothing is wrong with a qjet don't ever replace it.
09-19-2012, 05:41 PM
#23
Melting Slicks
I think I miss understood the offer.
09-19-2012, 06:09 PM
#24
Race Director
I chose a bad core to build up for my new combination. Was going to take care of it last week but I got a chest injury that's keeping me away from turning wrenches for a bit. 
FWIW, I think you will lose a bit of power. Sounds like you're pulling well over 400whp and I think the Q-Jet is going to lose the edge at that point.
FWIW, I think you will lose a bit of power. Sounds like you're pulling well over 400whp and I think the Q-Jet is going to lose the edge at that point.
09-19-2012, 06:47 PM
#25
Race Director
Here is a link from 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 514tq 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
Last edited by 63mako; 09-19-2012 at 06:50 PM.
09-19-2012, 10:17 PM
#27
Safety Car
09-20-2012, 01:44 AM
#28
Team Owner
Wall Street thinks so....at the expense of the rest of the country. 
09-20-2012, 12:23 PM
#30
Race Director
The secondary airvalve system on QJets helps simulate this characteristic of EFI, but it's still a compromise.
I want to master this QJet stuff... but if I could legally switch to EFI on my 78 I'd be running something already.
09-20-2012, 01:29 PM
#31
Tech Contributor
Member Since: Aug 1999
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Yes. I have seen Q jets running in the 10's. They are good carbs and will run with anything to a point. You go in the pits at the drag strip you won't see one anymore but back in the 70's there were a lot of them. I am not knocking Holleys or Barry Grant carbs but a properly tuned Qjet will run with most anything in a street/strip engine. Your over 500 Hp and the Demon will probably be a better choice at that power level.
Here is a link from Cliff Ruggles.
Here is a link from Cliff Ruggles.
Lars
09-20-2012, 02:14 PM
#32
Drifting
Lars thank you so much for all the data and papers you have written. You really do provide an unbiased analysis of all the popular carbs.
Lars, I am going to paraphrase you for a moment because it was a very profound statement when you said something like "Get the unit you are comfortable with and can tune properly".
One of the reasons I switched to a Holley was because my car would have to crank a little extra if I let it set for a week or two. You pointed out that the qjet accelerator pump inlet is midway up the fuel bowl vs at the bottom of the bowl of a Holley. I actually think that is a pretty big deal for a couple of reasons. Once I got the Holley I found it was easier to dial it in for me.
I like the externally adjustable floats, accelerator pump cam and nozzle system, quick change secondary springs and easy to change jets. The design of the Holley was easier and seemed more flexible to me.
That said, there is plenty of tuning data for the quad and holley. Perhaps there is an edelbrock carb paper, I just haven't seen it.
Lars, I am going to paraphrase you for a moment because it was a very profound statement when you said something like "Get the unit you are comfortable with and can tune properly".
One of the reasons I switched to a Holley was because my car would have to crank a little extra if I let it set for a week or two. You pointed out that the qjet accelerator pump inlet is midway up the fuel bowl vs at the bottom of the bowl of a Holley. I actually think that is a pretty big deal for a couple of reasons. Once I got the Holley I found it was easier to dial it in for me.
I like the externally adjustable floats, accelerator pump cam and nozzle system, quick change secondary springs and easy to change jets. The design of the Holley was easier and seemed more flexible to me.
That said, there is plenty of tuning data for the quad and holley. Perhaps there is an edelbrock carb paper, I just haven't seen it.
09-21-2012, 12:07 PM
#35
Race Director
09-21-2012, 12:56 PM
#36
Race Director
Cliff and I have both documented exactly the same results, and I've even posted back-to-back Q-Jet & Holley dyno results right here in this Forum. In spite of me posting actual numbers from actual testing, people will still believe whatever bench racing myths they wish to cling to - not that they'll actually back anything up with real test results. I've tested, and I've posted the results, just as Cliff has. And this arguement will go on in complete disregard to the test data...
Lars
Lars
09-21-2012, 03:15 PM
#38
Race Director
I think it will beat it in response and it'll be close, within the margin of error, as to how it'll do at the strip/dyno.
Small primaries can do a lot for throttle response.
09-21-2012, 03:28 PM
#39
Racer
You guys are far beyond me in knowledge in ref. to carbs. I just want to know why more guys aren't using Q-jets at the drag tracks. The guys who are winning at the big tracks know their stuff when it comes to carbs, and even though it's harder to dial-in a Q-jet, you'd think they would beable to get the job done. And even though there is little advertisement f/ the Q-jet and therefore less aftermarket hype, if the guys who are "winning f/ the money" would be winning more w/ a Q-jet, wouldn't they be running the Q-jet rather than other available carbs? I know quite afew guys who are very knowledgable and who aren't sponsered, and if they could run faster w/ a Q-jet, you bet they would be doing it. Are Q-jets a bettter application on certain engines and not f/ others? In this day and age, if Q-jets were a faster application, they would be known as such. I personally have had good luck w/ all of them, Q-jet, AFB, Edelbrock, etc., but just like was stated here, the AFB/Edelbrock type design is easier to work on, and the Q-jet took some doing. Just asking afew questions as I know you guys are up on this stuff. Thanks in advance.