Quadrajet or Holley
#22
Melting Slicks
I did a shoot out at the drag strip last September with my 800 cfm Quadrajet versus my 800 DP Holley. The Qjet was quicker and faster by .04 sec and .3 mph (11.96 @115.30 versus 12.00 @ 115.0), and it gets better mileage!
Take a look at one of my Quadrajet runs last May - it's not quite as fast but the humidity was higher...
http://www.youtube.com/watch?v=7FNC9tILoo0
Tuning the Qjet at the track is quite simple by changing secondary rods; compare that to changing secondary and/or primary jets in a Holley. And, with a Qjet, you don't spill gas all over your engine.
Because I have an Air-to-Fuel indicator in the car, I've learned that the metering with the Qjet is really good - I haven't used any better carburetor!
Take a look at one of my Quadrajet runs last May - it's not quite as fast but the humidity was higher...
http://www.youtube.com/watch?v=7FNC9tILoo0
Tuning the Qjet at the track is quite simple by changing secondary rods; compare that to changing secondary and/or primary jets in a Holley. And, with a Qjet, you don't spill gas all over your engine.
Because I have an Air-to-Fuel indicator in the car, I've learned that the metering with the Qjet is really good - I haven't used any better carburetor!
#23
I did a shoot out at the drag strip last September with my 800 cfm Quadrajet versus my 800 DP Holley. The Qjet was quicker and faster by .04 sec and .3 mph (11.96 @115.30 versus 12.00 @ 115.0), and it gets better mileage!
Take a look at one of my Quadrajet runs last May - it's not quite as fast but the humidity was higher...
http://www.youtube.com/watch?v=7FNC9tILoo0
Tuning the Qjet at the track is quite simple by changing secondary rods; compare that to changing secondary and/or primary jets in a Holley. And, with a Qjet, you don't spill gas all over your engine.
Because I have an Air-to-Fuel indicator in the car, I've learned that the metering with the Qjet is really good - I haven't used any better carburetor!
Take a look at one of my Quadrajet runs last May - it's not quite as fast but the humidity was higher...
http://www.youtube.com/watch?v=7FNC9tILoo0
Tuning the Qjet at the track is quite simple by changing secondary rods; compare that to changing secondary and/or primary jets in a Holley. And, with a Qjet, you don't spill gas all over your engine.
Because I have an Air-to-Fuel indicator in the car, I've learned that the metering with the Qjet is really good - I haven't used any better carburetor!
#24
Interesting results and informative. However not conclusive. On another day the results could have been reversed or even equal. Four one hundreths of a second is really splitting hairs and I'll bet either combo can't run within .04 of exact repeatability. I'd say they're even.
#25
I gotta lean towards the Q-Jet side. But I disagree that it takes an expert to make it perform great. I had problems with my original q-jet, so I looked into getting something like holley or whatever, I just wanted something that ran better. In the end I decided I would try and rebuild and tune the q-jet, worst case I just go with a new carb. I knew absolutely nothing about carbs, so I bought a book and ordered a rebuild kit from cliffs high performance. With the help of Cliff and this forum my Q-jet runs like a champ.
My Q-Jet performs great, and I am definitely no expert mechanic or carb guru. I guess there is pros and cons with both, it just comes down to preference.
Sean
My Q-Jet performs great, and I am definitely no expert mechanic or carb guru. I guess there is pros and cons with both, it just comes down to preference.
Sean
#26
the q-jet by far!!
a q-jet has no business running with a hipo cam but...when you send it to cliffs performance like i did...he totally redoes it and it idles better,crisper response better mileage and wll out power anything holly can throw at it...i never had a q-jet before only several hollys and proform and edlebrock carbs...out of the box i hated the q-jet but after he reworked it...wow all accross the board,he does what the carb shop in orange does but only with q-jets,go to his website google cliffs performance,youl lke when he does and youl be a believer,several circle race track racers have done that here too
#28
Drifting
With the help of Lars and Cliff, I rebuilt my Qjet. Cliff even custom lathed the primary power tip metering rods for me. The performance of the unit was perfect.
HOWEVER, since my car is not a daily driver and sits for a week or so sometimes, it would be hard to start. Lars explanation was simple, the accelerator pump inlet is in the middle of the fuel bowl in a quad. If the fuel evaporates past that level, no accelerator pump shot to start.
Holley on the other hand put the accelerator pump at the bottom.
Qjet has 2 settings for the accelerator pump arm. Holley has at least 7 different cams with 2 positions each to alter the pump shot.
Holley has different size squirters to further customize the accelerator pump.
Holley jets are cheap and easy to change. Some Qjet rods are no longer available but Cliff can custom lathe them for you...
The Qjet secondary air flap gets the carb its bad wrap and can be a bit of a challenge to adjust. Holley uses a spring system for its vacuum secondaries which is easy to customize.
And finally, there are many after market parts for a Holley that can help you to really dial in the carb if you want to play with it.
I changed to a Holley 4160 and have an O2 gauge. Its nothing special.
Idle 12.7 easy to change
cruise 13.8 easy to change
WOT 12.5 not so easy to change , but pretty good for performance.
HOWEVER, since my car is not a daily driver and sits for a week or so sometimes, it would be hard to start. Lars explanation was simple, the accelerator pump inlet is in the middle of the fuel bowl in a quad. If the fuel evaporates past that level, no accelerator pump shot to start.
Holley on the other hand put the accelerator pump at the bottom.
Qjet has 2 settings for the accelerator pump arm. Holley has at least 7 different cams with 2 positions each to alter the pump shot.
Holley has different size squirters to further customize the accelerator pump.
Holley jets are cheap and easy to change. Some Qjet rods are no longer available but Cliff can custom lathe them for you...
The Qjet secondary air flap gets the carb its bad wrap and can be a bit of a challenge to adjust. Holley uses a spring system for its vacuum secondaries which is easy to customize.
And finally, there are many after market parts for a Holley that can help you to really dial in the carb if you want to play with it.
I changed to a Holley 4160 and have an O2 gauge. Its nothing special.
Idle 12.7 easy to change
cruise 13.8 easy to change
WOT 12.5 not so easy to change , but pretty good for performance.
#29
Le Mans Master
When I was growing up, was led to believe Holleys were it. Later, when doing some strong street engine builds, learned that properly set Q-Jets were really it. The throttle response of these, feels like fuel injection. Cold starts really aren't a problem, as use rear mounted electric fuel pumps. Run the pump a few seconds, and starts up with a bump of the key. Also use a dash switch to stall out on an empty carb bowl when parking, so no crap gas left in there.
#30
ok,well im happy you got one you like,im getting another one,a 850 cfm q-jet for my 496 its in my 69 stingray,i have the patriot heads,625 lift, voo doo hyd. roller, weiand stealth, proform 900 cfm custamized by the card shop,it fits under a l-88 hood,i like it,its tremec tko 600 and 373 rear gear,it has lots of go,but im going to use a custimized q-jet in it instead of the proform
#31
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Last edited by lars; 06-17-2012 at 11:15 PM.
#32
Drifting
for those who missed it.
Your engine is a mild street build, and the Q-Jet will handle it just fine in near-stock trim. Set the carb up per the "Quickie Performance Setup" section of my Q-Jet paper, and you'll have a carb that will outperfrom the Holley across the rpm range for your street engine.
To prove that point, I just finished up another dyno test of a mildly-built 400, and the results follow…
The engine was a stock-block 400 with stock factory cast iron heads. I got compression ratio up to 10.08:1 with flat-top pistons and the stock deck height. The bottom-end was kept stock with some good rod bolts, and the heads were given a good 3-angle valve job. The restrictive EGR intake was scrapped and an Edelbrock “Performer” intake was used to keep overall engine height near-stock so that there would be no hood interference problems. The owner wanted a very mild cam to maintain engine vacuum and power brakes, so a mild hydraulic roller was used. No other trick parts – the engine was pretty much a modest compression 400 with a mild roller in it.
The real purpose of the dyno run was to get good numbers for the owner and to get a good tune on the engine, but we also wanted to get a back-to-back comparison of a well-tuned Q-Jet to a properly set up Holley of similar size. Those results came in as expected…
For the first “out-of-the-box” dyno pull, the Q-Jet was used (17056263). This carb is factory jetted at 70/42/DB, which is awfully lean. I re-jetted the carb to 76/42/DB with a 3/8” float level and .640 secondary rod height. Other carb tuning and parameters were set up exactly as outlined in my Q-Jet Tuning Paper under the “Quickie Performance Setup” section.
After getting the timing optimized (the inefficient chambers in the iron heads took 41 degrees total timing for best power and torque without detonation – an increase from my initial setting of 37). We were using 91-octane pump gas with 10% ethanol – right out of the gas station down the street. Total timing was coming in before 2000 rpm – a very quick curve.
Curve showing effect of 37 vesus 41 degrees of timing. Red line is 41 degrees timing:
The 4 initial pulls we did on the engine showed a “dip” in the torque curve (with resulting “sag” in the power curve) between 3500 and 4000. This is right where the Q-Jet secondary airvalve is starting to open up, and the air/fuel numbers were showing a lean condition right at the tip-in of the secondaries. The stock “DB” secondary rods in the carb have the “short” power tips, which delay fuel enrichment. We installed a pair of Edelbrock “CL” rods which have about the same diameter (just a small tad richer), but they have the “long” power tips. Richening up the secondary tip-in point really flattened out the torque curve and made the power curve a near straight-line shot towards the top.
Curve showing effect of "tweaking" the Q-Jet secondary rods:
Once this had been sorted out and the Q-Jet was correctly tuned, I wanted to do the final run just to prove one of my pet-peeve points: Q-Jets are garbage, and any Holley will outperform a Q-Jet… blah, blah, blah… As I state in all my seminars and papers, a properly tuned Q-Jet will perform almost identical to a properly tuned Holley, except that the Q-Jet tends to produce better torque and throttle response in the low and mid range in a street driven vehicle than the Holley. Now that we had our Q-Jet pretty well dialed in, it was time for a switch to the Holley.
The Holley I selected was a 3310-1, which is a 750 vacuum secondary with the secondary metering block (not the cheap plate). The carb was set up and tuned to spec with 72 primary jets, 80 secondary, and the “tall yellow” secondary spring was selected to assure that the secondaries would actually open. Choke system was removed to give it all the airflow advantage it could get. Float levels, shooters, and all tuning parameters were all set up correctly and verified and “blessed” by noted NASCAR engine builder Steve Yacki (who was also our dyno operator this day). The Holley was given 2 pulls on the dyno, and we verified that the air/fuel ratio on the Holley was virtually identical to the Q-Jet: The A/F numbers matched exactly at many data points, and were never different by more than 0.5:1 at any time through the entire rpm range – the 2 carbs were metering air and fuel at exactly the same ratio, so there was no “fudging” any numbers on these pulls.
The Q-Jet bettered the Holley by 15 ft/lbs of torque on the bottom end, and pulled more than 20 ft/lbs at many data points, with a 10 to 20 horsepower gain over the Holley at many points through the range. The Holley produced a couple of peak numbers at limited points, but not enough to give it any advantage over the Q-Jet. The mass airflow numbers through the Holley were also lower than the airflow numbers through the Q-Jet at high rpm, and this can be seen by the drop-off in the Holley performance at the top of the curve. We even did one Holley run with me forcing the secondaries fully open for the top ½ of the rpm range, but this killed all the top-end numbers completely: The carb liked the “tall yellow” spring.
The numbers between the two carbs are fairly close, but if these 2 engines had been installed in 2 identical street cars, the Q-Jet car would have come across the finish line ahead of the Holley car by a significant margin.
This is not to say that either carb is “better.” But the fact is, that if you set these carbs up correctly, and know how to tune them, they can be made to run very well. There is no point in replacing a badly-tuned Q-Jet with a badly-tuned Holley or vice versa. A well-tuned Holley will run better than a badly-tuned Q-Jet, and this is what is usually the case in the “Holley is better than that crap Q-Jet” argument. If you have a good Q-Jet and know how to set it up, run it on your street car. If you don’t have a carb, or don’t know how to tune a Q-Jet, a Holley will run fine, but you better be able to tune it, too. Black lines are Q-Jet, green lines are Holley:
Lars
To prove that point, I just finished up another dyno test of a mildly-built 400, and the results follow…
The engine was a stock-block 400 with stock factory cast iron heads. I got compression ratio up to 10.08:1 with flat-top pistons and the stock deck height. The bottom-end was kept stock with some good rod bolts, and the heads were given a good 3-angle valve job. The restrictive EGR intake was scrapped and an Edelbrock “Performer” intake was used to keep overall engine height near-stock so that there would be no hood interference problems. The owner wanted a very mild cam to maintain engine vacuum and power brakes, so a mild hydraulic roller was used. No other trick parts – the engine was pretty much a modest compression 400 with a mild roller in it.
The real purpose of the dyno run was to get good numbers for the owner and to get a good tune on the engine, but we also wanted to get a back-to-back comparison of a well-tuned Q-Jet to a properly set up Holley of similar size. Those results came in as expected…
For the first “out-of-the-box” dyno pull, the Q-Jet was used (17056263). This carb is factory jetted at 70/42/DB, which is awfully lean. I re-jetted the carb to 76/42/DB with a 3/8” float level and .640 secondary rod height. Other carb tuning and parameters were set up exactly as outlined in my Q-Jet Tuning Paper under the “Quickie Performance Setup” section.
After getting the timing optimized (the inefficient chambers in the iron heads took 41 degrees total timing for best power and torque without detonation – an increase from my initial setting of 37). We were using 91-octane pump gas with 10% ethanol – right out of the gas station down the street. Total timing was coming in before 2000 rpm – a very quick curve.
Curve showing effect of 37 vesus 41 degrees of timing. Red line is 41 degrees timing:
The 4 initial pulls we did on the engine showed a “dip” in the torque curve (with resulting “sag” in the power curve) between 3500 and 4000. This is right where the Q-Jet secondary airvalve is starting to open up, and the air/fuel numbers were showing a lean condition right at the tip-in of the secondaries. The stock “DB” secondary rods in the carb have the “short” power tips, which delay fuel enrichment. We installed a pair of Edelbrock “CL” rods which have about the same diameter (just a small tad richer), but they have the “long” power tips. Richening up the secondary tip-in point really flattened out the torque curve and made the power curve a near straight-line shot towards the top.
Curve showing effect of "tweaking" the Q-Jet secondary rods:
Once this had been sorted out and the Q-Jet was correctly tuned, I wanted to do the final run just to prove one of my pet-peeve points: Q-Jets are garbage, and any Holley will outperform a Q-Jet… blah, blah, blah… As I state in all my seminars and papers, a properly tuned Q-Jet will perform almost identical to a properly tuned Holley, except that the Q-Jet tends to produce better torque and throttle response in the low and mid range in a street driven vehicle than the Holley. Now that we had our Q-Jet pretty well dialed in, it was time for a switch to the Holley.
The Holley I selected was a 3310-1, which is a 750 vacuum secondary with the secondary metering block (not the cheap plate). The carb was set up and tuned to spec with 72 primary jets, 80 secondary, and the “tall yellow” secondary spring was selected to assure that the secondaries would actually open. Choke system was removed to give it all the airflow advantage it could get. Float levels, shooters, and all tuning parameters were all set up correctly and verified and “blessed” by noted NASCAR engine builder Steve Yacki (who was also our dyno operator this day). The Holley was given 2 pulls on the dyno, and we verified that the air/fuel ratio on the Holley was virtually identical to the Q-Jet: The A/F numbers matched exactly at many data points, and were never different by more than 0.5:1 at any time through the entire rpm range – the 2 carbs were metering air and fuel at exactly the same ratio, so there was no “fudging” any numbers on these pulls.
The Q-Jet bettered the Holley by 15 ft/lbs of torque on the bottom end, and pulled more than 20 ft/lbs at many data points, with a 10 to 20 horsepower gain over the Holley at many points through the range. The Holley produced a couple of peak numbers at limited points, but not enough to give it any advantage over the Q-Jet. The mass airflow numbers through the Holley were also lower than the airflow numbers through the Q-Jet at high rpm, and this can be seen by the drop-off in the Holley performance at the top of the curve. We even did one Holley run with me forcing the secondaries fully open for the top ½ of the rpm range, but this killed all the top-end numbers completely: The carb liked the “tall yellow” spring.
The numbers between the two carbs are fairly close, but if these 2 engines had been installed in 2 identical street cars, the Q-Jet car would have come across the finish line ahead of the Holley car by a significant margin.
This is not to say that either carb is “better.” But the fact is, that if you set these carbs up correctly, and know how to tune them, they can be made to run very well. There is no point in replacing a badly-tuned Q-Jet with a badly-tuned Holley or vice versa. A well-tuned Holley will run better than a badly-tuned Q-Jet, and this is what is usually the case in the “Holley is better than that crap Q-Jet” argument. If you have a good Q-Jet and know how to set it up, run it on your street car. If you don’t have a carb, or don’t know how to tune a Q-Jet, a Holley will run fine, but you better be able to tune it, too. Black lines are Q-Jet, green lines are Holley:
Lars
#36
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Last edited by lars; 06-17-2012 at 11:15 PM.
#39
Tech Contributor
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 13,654
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Deleted by Lars. E-Mail me if you need carb & tuning info info.
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Last edited by lars; 06-17-2012 at 11:14 PM.