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Quadrajet vs holley street avenger

Qjet or holley

  • Qjet

    Votes: 13 100.0%

  • Holley street avenger 670cfm

    Votes: 0 0.0%
  • Total voters
    13
MetalMulishaMarcus

MetalMulishaMarcus

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I have a bone stock 350 in my k5 with a Qjet. I was recently given a holley street avenger 670cfm that i rebuilt.

My question is, if i switch carbs will i see any performance gains?
Will i lose performance?
Is the holley to big for my stock 350?

Also, i may have a line on some cheap headers, would that change the performance of either carb?

Thanks!
 
MetalMulishaMarcus said:
I have a bone stock 350 in my k5 with a Qjet. I was recently given a holley street avenger 670cfm that i rebuilt.

My question is, if i switch carbs will i see any performance gains?
Will i lose performance?
Is the holley to big for my stock 350?

Also, i may have a line on some cheap headers, would that change the performance of either carb?

Thanks!
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Unless the q-jet is in poor condition, I wouldn’t touch it. I personally hate Holley except for racing.
 
Fastereddie said:
Unless the q-jet is in poor condition, I wouldn’t touch it. I personally hate Holley except for racing.
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I would pay to get the throttle plate bushings put in, if it was needed in the Q-jet, before I tried a free Holley. They may make more power at top end, but the driving experience with one was no good.
 
83ChevyK5Blazer said:
I also prefer a good qjet to any aftermarket, my 350, and now 454 get decent mileage, and have enough get up and go when it opens up. Plus they work the best for offroad.
I hated my edelbrock carb on and off road.
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Then leave it as is.
:saweet:

I get along good with my Edelbrock on my C10, but I doesn't go offroad.
 
Qjet

Also worth noting, the Qjet is probably the 750 cfm variety. If it doesn’t leak vacuum around the throttle plate bushings, and you can tune it, run it
 
I plan on keeping my Qjet especially since its running really good.

I just wanted to see if i would gain anything from putting on a holley.
 
MetalMulishaMarcus said:
I plan on keeping my Qjet especially since its running really good.

I just wanted to see if i would gain anything from putting on a holley.
Click to expand...
Typically you gain more trips to the gas station. Every Qjet application I’ve had ran a bit higher mpg than the Holley

Throttle response might be better on the Q


Plus the cool noises mentioned above
 
Bent77 said:
Typically you gain more trips to the gas station. Every Qjet application I’ve had ran a bit higher mpg than the Holley

Throttle response might be better on the Q


Plus the cool noises mentioned above
Click to expand...

I like the fact you can adjust when the secondary air valve actually opens.
 
Is it an electronic q-jet? If so, trash now. If it's older, run it. I doubt you'd notice a performance difference unless you know a Holley whisperer. I know of only 1 old guy that can perform such magic.

I'm running the Summit version of a Holley on my ZZ4 and don't care for it. I need to rebuild the q-jet and toss it back on.
 
In my opinion….. Being a stock motor I’d stick with the qjet, if the motor was modified the a Holley might make a difference depending on cfm (vs qjet) and/or choke and secondary configuration.

I run a pro built qjet on my big block and it runs good and has great manners. That said, I feel like it’s lazy between part and wide open throttle. I just bought a Holley that is very different from the qjet that I’m hoping will make a noticeable difference in the road performance of my motor. For now though, I’m going to keep the qjet in case I decide to go back.
 
nvrenuf said:
In my opinion….. Being a stock motor I’d stick with the qjet, if the motor was modified the a Holley might make a difference depending on cfm (vs qjet) and/or choke and secondary configuration.

I run a pro built qjet on my big block and it runs good and has great manners. That said, I feel like it’s lazy between part and wide open throttle. I just bought a Holley that is very different from the qjet that I’m hoping will make a noticeable difference in the road performance of my motor. For now though, I’m going to keep the qjet in case I decide to go back.
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You can adjust the front power circuit and how fast the secondaries open on that Qjet
 
quad. all. day. IMO.

and for the record, the 2 may be spec'd/set up different, thus maybe some performance difference.. but they are both just fuel delivery systems and can be modded as such.. hangars, jets, etc, etc... they technically don't make any of the power decisions, just supply what the cam, heads and boom chamber want....
 
Bent77 said:
You can adjust the front power circuit and how fast the secondaries open on that Qjet
Click to expand...

Yeah but I have negative qjet skills. lol
I’m going to try dumping fuel in and seeing how I like. I feel like I can resell the Holley and be ok if I don’t like it off road.
 
Try this instead:
With it running, crack the throttle with your hand and get a feel for where that “dead” spot is. Often you can feel it, but also see where and whats going on

If it’s happening as the secondaries open, crack the throttle again but this time, hold your hand over the secondary plate.

If it improves, it means its lean on the back. You can do one of a few things: smaller rod, shorter hanger, or slow down the opening

If it happens before the secondaries open, hold your hand over the front. Same deal. Better means its too lean, worse too rich
 
nvrenuf said:
@Bent77 me or MMM (op)?
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That was directed at you, but the theory is a constant. Your hand works like a choke plate: slows the air down and lets the fuel catch up. Allows you to get a feel, as the jetting can be off in the opposite direction of how the power circuit or accelerator circuit is, so reading the plugs won’t necessarily help you
 
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