I'm Running a Q-jet on my 5.3 and Love it
07-04-2012, 06:53 PM
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I'm Running a Q-jet on my 5.3 and Love it I've seen people asking about running a Q-jet, I've gotten mixed answers but I've never seen anyone actually do it..
I did... I'm running a 1968 Q-jet from a stock Vette 350 and it absolutely runs like a champ.. WAYY better than the Holley 750.. No matter what I did to that carb it ran ok...but PIG rich...
The only downfall is I had to run a shitty adapter.. but i don't even notice it..
I used an Olds 307 throttle bracket (for the correct geometry for the Th2004r TV cable) and fuel pressure is set at 6PSI
Ultimately this setup is as close as im going to get vs EFI but its a hoot.. Im currently doing my research and I plan on going back to EFI but I still have some learning to do.. so in the mean time Ill play with carbs..
Heres a pic and some video
I did... I'm running a 1968 Q-jet from a stock Vette 350 and it absolutely runs like a champ.. WAYY better than the Holley 750.. No matter what I did to that carb it ran ok...but PIG rich...
The only downfall is I had to run a shitty adapter.. but i don't even notice it..
I used an Olds 307 throttle bracket (for the correct geometry for the Th2004r TV cable) and fuel pressure is set at 6PSI
Ultimately this setup is as close as im going to get vs EFI but its a hoot.. Im currently doing my research and I plan on going back to EFI but I still have some learning to do.. so in the mean time Ill play with carbs..
Heres a pic and some video
07-04-2012, 08:47 PM
#3
I had a 750 holley on my 5.3 because that's all I had and it was fat like I knew it should be. Went to a 650 and runs like it should. At least you won't get gas everywhere.
07-04-2012, 09:15 PM
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Thank you for your praises guys! I have great vacuum but I believe its just the perfect carb for my setup...
I mean I know the hardcore guys go with Holleys and thats just how it is.. I too ran the 750 because thats all I had to play with and while it ran ok.. It would load up on the freeway cruising... Id cruise then step into it a bit to pass a car and it would load then clear out and go... The Q is just happy all over.. I have sloppy throttle shafts which I plan to correct but other than that I never thought it would run as well as it does
I mean I know the hardcore guys go with Holleys and thats just how it is.. I too ran the 750 because thats all I had to play with and while it ran ok.. It would load up on the freeway cruising... Id cruise then step into it a bit to pass a car and it would load then clear out and go... The Q is just happy all over.. I have sloppy throttle shafts which I plan to correct but other than that I never thought it would run as well as it does
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07-05-2012, 02:25 AM
#8
If it work it works. Having complaints of a 750 on a 5.3 are common as they are usually set up for large engines. But a 650 Holley is usually great. I want to try a edelbrock on my 4.8 but then the TPS bracket and sensor will need to be some how made to work..again.
07-05-2012, 07:57 AM
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Well ya I figured it would be bad in regards to mileage but I tried it anyways... the q jet is a superior street Carb however the square bore manifold was my only issue
07-05-2012, 01:37 PM
#10
Superior? No idea. I know a vac sec Holley and a q jet are both street oriented, and I'm sure they boil down to the tune. If one or the other is off, it is the better tuned that would surely win. We are talking controlled fuel leak either way. Never seen a comparrison on the same engine.
07-06-2012, 10:55 AM
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The quadrajet is superior street Carb for the simple fact GM spent countless time and money on the Carb which served on many vehicles from grandmas grocery getter to many hot rods of yesterday...and its street oriented life span lasted for almost 30yrs from the factory.
Holley doesn't have the same cred in that respect. For racing there is no doubt Holley is.the top.dog
But on the street the quad wins
Holley doesn't have the same cred in that respect. For racing there is no doubt Holley is.the top.dog
But on the street the quad wins
07-06-2012, 01:43 PM
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That's because they're designed for specific applications...I too have run into issues with used carbs but a stock 350 Carb on a mild 5.3 just happened to work for me.
07-06-2012, 02:16 PM
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Lots of people seem to think that the VS Holleys can't be tuned to run comparable to OEM, even on a mild/street combo.....I disagree. It just takes time and proper size selection. Everyone thinks they need a 750cfm for the street, even with small cubes and relatively low redlines. I assume this is because all the factory issued Q-jets (other than the rare 800s) are 750s, even on small engines, so people feel that a 750 square bore will also be fine with vacuum control over the secondaries. I disagree. Q-jet is a spread bore, so the primaries are small and will respond well at part throttle even with small displacement. A 750 square bore obviously uses bigger primaries than a 750 Q-jet, so throttle response will be less crisp with a small(er) engine. If some of the guys that have poor street manners with a 750 Holley on their small displacement street engines would just try a 650 or even 600, I think they would be surprised at how good it could run with some tuning. Granted this may not be the best course if you rev to 7000rpm though.
There is no arguing the fact that a Q-jet will offer superior MPG over most aftermarket carbs, but too many people just give up on their Holley thinking that it just can't be tuned well for the street even on a rather mild combo. Often I think this is because they are overshooting their cfm requirements, and jump right to a 750 for street applications, even with small cubes and relatively low redlines. Another part of the issue is bad tuning habits people have delevoped for Holleys, some of which were perpetuated by Holley themselves (such as their poor recommendation for power valve selection).
Either way, Q-jet is certainly a good carb, offering OEM engineering, best potential MPG, and will run well on a wide range of engine sizes and applications...no arguements there. But Holleys can be excellent street carbs as well, when properly sized and tuned.
There is no arguing the fact that a Q-jet will offer superior MPG over most aftermarket carbs, but too many people just give up on their Holley thinking that it just can't be tuned well for the street even on a rather mild combo. Often I think this is because they are overshooting their cfm requirements, and jump right to a 750 for street applications, even with small cubes and relatively low redlines. Another part of the issue is bad tuning habits people have delevoped for Holleys, some of which were perpetuated by Holley themselves (such as their poor recommendation for power valve selection).
Either way, Q-jet is certainly a good carb, offering OEM engineering, best potential MPG, and will run well on a wide range of engine sizes and applications...no arguements there. But Holleys can be excellent street carbs as well, when properly sized and tuned.
07-06-2012, 06:50 PM
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Lots of people seem to think that the VS Holleys can't be tuned to run comparable to OEM, even on a mild/street combo.....I disagree. It just takes time and proper size selection. Everyone thinks they need a 750cfm for the street, even with small cubes and relatively low redlines. I assume this is because all the factory issued Q-jets (other than the rare 800s) are 750s, even on small engines, so people feel that a 750 square bore will also be fine with vacuum control over the secondaries. I disagree. Q-jet is a spread bore, so the primaries are small and will respond well at part throttle even with small displacement. A 750 square bore obviously uses bigger primaries than a 750 Q-jet, so throttle response will be less crisp with a small(er) engine. If some of the guys that have poor street manners with a 750 Holley on their small displacement street engines would just try a 650 or even 600, I think they would be surprised at how good it could run with some tuning. Granted this may not be the best course if you rev to 7000rpm though.
There is no arguing the fact that a Q-jet will offer superior MPG over most aftermarket carbs, but too many people just give up on their Holley thinking that it just can't be tuned well for the street even on a rather mild combo. Often I think this is because they are overshooting their cfm requirements, and jump right to a 750 for street applications, even with small cubes and relatively low redlines. Another part of the issue is bad tuning habits people have delevoped for Holleys, some of which were perpetuated by Holley themselves (such as their poor recommendation for power valve selection).
Either way, Q-jet is certainly a good carb, offering OEM engineering, best potential MPG, and will run well on a wide range of engine sizes and applications...no arguements there. But Holleys can be excellent street carbs as well, when properly sized and tuned.
There is no arguing the fact that a Q-jet will offer superior MPG over most aftermarket carbs, but too many people just give up on their Holley thinking that it just can't be tuned well for the street even on a rather mild combo. Often I think this is because they are overshooting their cfm requirements, and jump right to a 750 for street applications, even with small cubes and relatively low redlines. Another part of the issue is bad tuning habits people have delevoped for Holleys, some of which were perpetuated by Holley themselves (such as their poor recommendation for power valve selection).
Either way, Q-jet is certainly a good carb, offering OEM engineering, best potential MPG, and will run well on a wide range of engine sizes and applications...no arguements there. But Holleys can be excellent street carbs as well, when properly sized and tuned.
07-30-2012, 09:11 PM
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Carb Hi guys... I'm running a Q-jet of an 86 chevy 1 ton dually 4x4 on my LS3. Its an 800,,I've recalibrated it. My Ls has Lingenfelter stage III heads,10.5 compression,,A comp cams xer278 cam,,I think. Idle vacuum is only 12" @ 850rpm. Light power piston spring to keep rods down at idle,,adjust power piston half to 1 turn up from bottom etc. Did alot of tuning to mine,running a built non electronic 700r4,with a lock up convertor on a switch that I control.Carb is on a GMPP LSX intake and I run an adapter like yours. I get 16-17 mpg,,Runs stupid fast,,Oh yea,Its in my 82 jeep CJ7 street toy. Will destroy 35's if I let it,will pull the front wheels outa the hole if launched hard. Mosier 35 spline dana 60 in back and waggoneer dana 44 in front with 4:10's. Tried 2 holleys,,,POS. I did end up putting a divider in the carb adapter to increase my vacuum signal to the carb and to help bottom end torque. I've suprised More than a couple of mustangs and camaros,,and alot of trucks... End result ,,,Q-JETS??? Hell yes!!!
