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What carb for 454

Chickntrk said:
What avenger do you have? Street? Truck? Edlebrocks suck off road as you found out. I have been running holley truck avengers for years and have never had an issue but you do have to work with them to get them right
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It’s the truck 4x4. But I bought it used and it’s the 670cfm. It never ran like the Edelbrock on level surface. That’s what I want. I see Holly has another one but 770cfm. I’m going to look at that one, but dang it’s expensive. I’m also going to get a spacer this time. I believe that would help.
 
@77snowwheeler fyi, Holley's website has a refurb page so if you have time I'd watch it to see if anything suitable is posted.

Is there anything wildly different about the Avenger series carbs other than the vent tube and (maybe) internal jet / vent extensions? If that's all maybe consider a "regular" carb and add the extensions and loop the vent tube (with breather holes). I also would not be afraid of a larger carb like a 750-800 cfm, I've seen more than one Engine Masters video (not Bible but worthy of noting) where they showed that a bigger than necessary carb worked IF jetted / tuned correctly. The motor will only use the cfm it needs so too small is bad but too big is ok within reason.
 
77snowwheeler said:
It’s the truck 4x4. But I bought it used and it’s the 670cfm. It never ran like the Edelbrock on level surface. That’s what I want. I see Holly has another one but 770cfm. I’m going to look at that one, but dang it’s expensive. I’m also going to get a spacer this time. I believe that would help.
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Stay away from the 770 truck avenger. I love Holley's and I know them well, but that particular carb does not have high speed airbleeds and it will be a constant compromise. I changed jets, pump cams, accelerator pumps, vacuum springs, etc. I got it running much better but the fuel curve is still way off because of the lack of air bleeds, and there is nothing you can do about that, without air bleeds.

Vacuum secondary carbs are less sensitive to being too large, because they only open based on airflow. Double pumpers are a little more sensitive, but generally have better throttle response and power when tuned correctly.
 
nvrenuf said:
@77snowwheeler fyi, Holley's website has a refurb page so if you have time I'd watch it to see if anything suitable is posted.

Is there anything wildly different about the Avenger series carbs other than the vent tube and (maybe) internal jet / vent extensions? If that's all maybe consider a "regular" carb and add the extensions and loop the vent tube (with breather holes). I also would not be afraid of a larger carb like a 750-800 cfm, I've seen more than one Engine Masters video (not Bible but worthy of noting) where they showed that a bigger than necessary carb worked IF jetted / tuned correctly. The motor will only use the cfm it needs so too small is bad but too big is ok within reason.
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I like the way you think. Now it’s about how to understand what you just said? Lol the floats are definitely different on the truck Holly. They’re float, design is for the hydrolic jumping cars and extreme angles for hill climbing, which the 670cfm, I have has proven that. Amazingly.
 
folkenheath said:
Stay away from the 770 truck avenger. I love Holley's and I know them well, but that particular carb does not have high speed airbleeds and it will be a constant compromise. I changed jets, pump cams, accelerator pumps, vacuum springs, etc. I got it running much better but the fuel curve is still way off because of the lack of air bleeds, and there is nothing you can do about that, without air bleeds.

Vacuum secondary carbs are less sensitive to being too large, because they only open based on airflow. Double pumpers are a little more sensitive, but generally have better throttle response and power when tuned correctly.
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That’s what I need. Electric choke and vacuum secondaries. So, that’s concerning, you’re against the truck avenger. What would you recommend considering hill climbing?
 
Are you talking hill climb racing or just climbing hills slowly for fun?
 
I’m running a 470 truck avenger on a 350…..before that I was running a 600 cfm regular Holley 4150 which did okay in most situations but on really steep climbs or really steep descents it would stall. I had an edlebrock on it for a week, it worked great on the street but off road it was trash, a bumpy road would cause it to cut out and carry on….edlebrock makes an off road kit but from what I’ve seen and heard it doesn’t help much.

I agree with @folkenheath the TA will always be a compromise somewhere, it’s hard to make a carb that can climb almost vertical and also perform well on the street, hence the TA and the SA series
 
77snowwheeler said:
Recreational hill climbs. Slow.
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Then my first choice would be EFI and my second choice would be Qjet.

The Qjet is not too small because of it's large secondaries, and works reasonably well offroad. Though I have no experience tuning them. A Holley I feel I can rebuild with my eyes shut, but not a Qjet. I personally take them off and use a Holley for performance.

But I have since converted everything to EFI and don't look back. Without venturis you can max airflow and pressurized fuel rails don't care what angle they are at.
 
folkenheath said:
Then my first choice would be EFI and my second choice would be Qjet.

The Qjet is not too small because of it's large secondaries, and works reasonably well offroad. Though I have no experience tuning them. A Holley I feel I can rebuild with my eyes shut, but not a Qjet. I personally take them off and use a Holley for performance.

But I have since converted everything to EFI and don't look back. Without venturis you can max airflow and pressurized fuel rails don't care what angle they are at.
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Can you point me in the right direction for the qj. They make one for the newer Chevy’s with electric choke and vacuum secondaries, but there seems to be so many options. I’m just a simple guy. I probably wouldn’t notice if the truck was running slightly off, but I’d like to have something that would run decent in all situations, but wouldn’t have to be perfect, except stalling? I just time my truck to 13* tdc and it is running better, but now it seem like the 670, is lacking, and the secondary doesn’t seem to open that great. I truly believe this carb is not enough. Dang it. Also, should I use a spacer, or adapter to fit my intake? Will it go on my performer rpm duel plane intake ok. If I use a spacer, open or spreadbore? I just want to find something I can just open the box it comes in and put it on? Is that possible?
 
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I think having it really close when you drop it on means a custom build, which means waiting. Even JET "off-the shelf" is about 2 months out: https://www.jegs.com/i/JET-Performance/561/36003/10002/-1
I don't know anything about this company, but they are saying 16-18 weeks. https://quadrajetpower.com/chevrolet-1978-454-17058212/ And you're at about half the price of FI-Tech.

The fastest thing would be finding one already rebuilt and find somebody familiar with tuning them. The idle mixture you pretty much do in your driveway with a vacuum gauge. I feel like the accelerator pump is also pretty much done by seat of the pants DIY style. When it comes to rods/jets, it's kind of an art form - unless you have a wideband O2 sensor. Good luck finding somebody to work on it. Maybe there is a CK5 member not too far away that could help?
 
77snowwheeler said:
I just want to find something I can just open the box it comes in and put it on? Is that possible?
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With a carb, the short answer is no. I have yet to find a carb that is bolt on and go, even a custom build is going to require fine tuning to your engine. When I got my TA I had to adjust the choke, adjust the mixture, go up a jet size and adjust the float level up some.
 
I agree with @Chickntrk, you can get close if you wait for someone to build one specifically for you. Off the shelf, out of the box stuff isn't going to be turn key.

I had a qjet built by SMI years ago, I sent them a core for them to rebuild using a spec sheet with motor and truck details. I bolted it on, adjusted the idle / choke / mixture screws using a vac gauge and it runs good but it's always had a tiny stumble when shifting from 2-3 gear. I have found a local hot rodder that's supposed to be good with them so I plan to have him tune it at some point.
 
Chickntrk said:
With a carb, the short answer is no. I have yet to find a carb that is bolt on and go, even a custom build is going to require fine tuning to your engine. When I got my TA I had to adjust the choke, adjust the mixture, go up a jet size and adjust the float level up some.
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Oh, yes. I forgot those minor adjustments. But it seems like on the qj, you need your name rank and serial number before you can get the right one? Lol
 
Chickntrk said:
With a carb, the short answer is no. I have yet to find a carb that is bolt on and go, even a custom build is going to require fine tuning to your engine. When I got my TA I had to adjust the choke, adjust the mixture, go up a jet size and adjust the float level up some.
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May have to order the truck avenger and take my chances. I’m set up with dual plane intake and that’s the easiest way to go?
 
Is the manifold a spread bore or square?
I would also like to know what caused the stuck closed. Usually that is an obstruction to the linkage, or worn shaft bushings. You indicated that the carb was newish.
 
Wes Harden said:
Is the manifold a spread bore or square?
I would also like to know what caused the stuck closed. Usually that is an obstruction to the linkage, or worn shaft bushings. You indicated that the carb was newish.
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Square bore, dual plane. I think it was a backfire issue. Funny enough, I just adjusted my timing and now it’s running ok. No backfire. I still believe the carb isn’t allowing enough fuel, to the motor. I believe that’s why I need a 750, or larger. I took a chance on the 670, and it’s just not giving enough. Unless I can jet it to a 750, not sure I can?
 
77snowwheeler said:
Square bore, dual plane. I think it was a backfire issue. Funny enough, I just adjusted my timing and now it’s running ok. No backfire. I still believe the carb isn’t allowing enough fuel, to the motor. I believe that’s why I need a 750, or larger. I took a chance on the 670, and it’s just not giving enough. Unless I can jet it to a 750, not sure I can?
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I’m at 13 btd. Seems to like that.
 
No you can't add more air by jetting.
But you should really only miss the larger cfms at the upper rpm. Lower rpm should care about max cfm.
Now your air fuel mixture is effected by jetting. Which can cause some drivability issues.
 
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