Best carb replacement?
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Joined: Feb 2009
Posts: 50
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From: Midland TX
Best carb replacement?
Looking for a good replacement for the Q-Jet on my 73, 5.7 with auto tranny. Prefer something that would be a direct bolt-on. Let me know what you recommend. Thanks in advance!
Burning Brakes
Joined: Nov 2006
Posts: 893
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From: Orange Park Florida
I have a Holley 4160C. Less than 1 1/2 years old, always had idling/operating problems so I've had to rebuild it. Found silicone smeared inside the metering block - some kind of manufacturing problem. Carb never touched by anyone (out of the box onto the car.) Wrote several times to Holley, but NO responses. Auto choke operates at startup but once warm, choke plate opens fully but idle speed stays high. Have to hit gas pedal to drop to standard idle. Still not performing up to standard.
Le Mans Master
Joined: Nov 2008
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From: columbus oh
Melting Slicks
Joined: Mar 2006
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From: Orange Park Fl
I have a Holley 4160C. Less than 1 1/2 years old, always had idling/operating problems so I've had to rebuild it. Found silicone smeared inside the metering block - some kind of manufacturing problem. Carb never touched by anyone (out of the box onto the car.) Wrote several times to Holley, but NO responses. Auto choke operates at startup but once warm, choke plate opens fully but idle speed stays high. Have to hit gas pedal to drop to standard idle. Still not performing up to standard.
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Melting Slicks
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From: Orange Park Fl
Race Director
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From: Duvall, WA
Safety Car
Joined: Aug 2001
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From: Waterford Mi
I have a Holley 4175. Even though it is sold as a direct replacement it is not. First off, the tapped hole in the base for the master brake vacuum line is smaller so you will need an adaptor and bend the line to get it to fit. Next, the aircleaner will not sit flat without a spacer because the 73-75 aircleaners are smaller diameter then other years and they hit the vacuum secondary module. Last, plan on spending some time and money to tune it to you setup. The Holley runs very rich out of the box. I ended up changing the discharge nozzle from a 40 down to a 21. Then I changed the secondary metering plate to a 29.
Le Mans Master
Joined: Oct 2007
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From: RI, Now Franklin/Nashville TN
I have had a Holley 4175 spreadbore for 25 years on my 78 and it runs great. It was a direct bolt on with the only modification being the power source for the electric choke.It is also easy to change the idle jets and the vacuum secondary spring for faster or slower opening of the secondaries. I like its simplicity and performance!
Thread Starter
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Joined: Feb 2009
Posts: 50
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From: Midland TX
Thanks everyone! I've decided to go ahead and rebuild the Q-Jet that came with the car. I've heard alot of pros and cons about this carb but in the end it will probably perform as well as others mentioned. Again thanks for the advice and suggestions, greatly appreciated!
Pro
Joined: Feb 2009
Posts: 587
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From: Columbus Ohio
Thanks everyone! I've decided to go ahead and rebuild the Q-Jet that came with the car. I've heard alot of pros and cons about this carb but in the end it will probably perform as well as others mentioned. Again thanks for the advice and suggestions, greatly appreciated!
Good Move ! A rebuilt and properly adjusted Q-Jet should do everything you want .
Thread Starter
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Joined: Feb 2009
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From: Midland TX
Got it rebuilt today and back on, still seeing about a 50-60 rpm swing but I think that's going to be a vacuum leak possibly. Idle is smooth but getting about a 280 rpm drop when in gear with a little bit of a rough idle, any ideas?
Melting Slicks
Joined: May 2006
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From: Raleigh NC
St. Jude Donor '13-'14
You're going to see that drop in RPM with an auto. Check your timing.
Thread Starter
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Joined: Feb 2009
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From: Midland TX
That's next on the list, found a bad vacuum line and replaced (very weathered) thanks for the help! Would that create that much fluxuation at idle? The rpm drop in gear was mis stated earlier, it's more like 400 rpm drop. I guess I'm used to running fuel injected vehicles with electronic ignition not used to seeing that kind of rpm drop. Checked vacuum and it's running around 18-19# vac.
Last edited by MidTex73; Apr 5, 2009 at 06:59 PM.
Thread Starter
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Joined: Feb 2009
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From: Midland TX
Exactly, it seems to be a problem that keeps eluding me, I will set the timing tonight to see if that helps. It idles smooth at normal idle, but with that rpm drop and rough idle just doesn't seem right. Will keep you posted on what I find out. Thanks for everyone's input.