carb x change
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
You'd be far better off to have a quality overhaul and tune of your existing carb.
There is zero - zero - power to be gained in the swap, and I think you'll find by the time you sort out all the linkages and stuff you'll be sorry you did it...
There is zero - zero - power to be gained in the swap, and I think you'll find by the time you sort out all the linkages and stuff you'll be sorry you did it...
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
Holley 4175 on my 78 L-82 since 1985-great spreadbore Qjet replacement. Has run flawlessly for all these years. Linkage hooks right up. The fuel line will not hook directly into the 4175 like on the qjet. Much prefer over the qjet. 27 years experience with the 4175!!!!
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Also curious of why you'd want to do something like this. Q-Jets are one of the most sophisticated street carb designs ever made. Because of this, they're generally more difficult to properly set up for engine mods. Can be done though, and well worth the effort. You can throw all sorts of money at trying other things, but bettin' they wont be worth it.
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
I have read both books by roe and ruggles and all the papers from Grimsrud on the sublect. Its not hard to tune a qjet. Its just easier to tune a holley. And parts more common. What motivated me to switch personally was Lars pointing out that there was little performance difference on a dyno. However the accelerator pump inlet on a q jet is near the center of the bowl unlike the Holley which feeds from the bottom. This made a big difference in starting my car since it may sit for a week or so and helped with hot starts too. In both cases fuel would evaporate or boil out leaving no pump shot for the next start.
I am cheap though and bought 2 holley carbs on craigslist for $50 and then sold one for $50. No risk.
I am cheap though and bought 2 holley carbs on craigslist for $50 and then sold one for $50. No risk.
CF Community Team
Joined: Oct 2004
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From: Cape Cod, Mass.
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I put a spreadbore Holley on my 68 427/390. Pretty simple bolt on. The linkage was pretty straightforward. It felt like I bolted on 50 horsepower. The low and mid range torque improved significantly. Cold starts after sitting for a few days was far better.
Admittedly, I am comparing this to a Q-Jet that was not operating at 100% but there aren't too many people that know what they are doing with these carbs. I have always felt that bolting on a NEW carb is a significant performance improvement. I have had the Holley on the car for about 5 years and it has performed flawlessly
Admittedly, I am comparing this to a Q-Jet that was not operating at 100% but there aren't too many people that know what they are doing with these carbs. I have always felt that bolting on a NEW carb is a significant performance improvement. I have had the Holley on the car for about 5 years and it has performed flawlessly
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
This is kinda the point - comparing a new, healthy carb with one that's 30 years old doesn't really provide a valid comparison.
Unless the engine is going to see a lot of changes, the Q-Jet is a tough carb to beat. It is more difficult to tune, especially given limited parts availability and expertise, but once rebuilt and tuned it will deliver every day. The tiny primaries and huge secondaries are perfect for the street-driven 'Vette.
Unless the engine is going to see a lot of changes, the Q-Jet is a tough carb to beat. It is more difficult to tune, especially given limited parts availability and expertise, but once rebuilt and tuned it will deliver every day. The tiny primaries and huge secondaries are perfect for the street-driven 'Vette.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
Le Mans Master
Joined: Oct 2010
Posts: 6,936
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
i have used both.the Holley is easier and was quicker until, i put 77 jets in the primary side with smaller rods. drilled out the passages recommended in cliffs book.runs very well. i think the important point is, if you can find a quadrajet that hasn't been ruined.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
Just put a Holley on my AMC Eagle, runs like a brand new fuel injected car. Had one on my 70 Torino and loved it too. Super simple to rebuild as well. My Q-jet runs like crap, I'd put a holley on it if I wasn't planning on converting it to fuel injection.
