Carb suggestions
Thread Starter
Racer
Joined: Apr 2006
Posts: 300
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From: Joplin Missouri
Carb suggestions
I've seen similar post to this but I'm curious what people with similar set ups are using. I have a 74 with a 496 that dynoed at 603 hp. I'm using a weiand stealth intake. I currently have a Holley 4150 750 dp on it. This is great for the strip but no bueno for the street. I would like to still have electric choke and mechanical secondarys if possible. I don't have a brand preference just want it to work.
So what would be the best options for street use and still kick butt on the strip?
So what would be the best options for street use and still kick butt on the strip?
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
750 CFM is way too small for a healthy 496. Heck, I'll be installing >900 on my next street 427 currently in the works. That said, if good manners and decent MPG without giving up too awful much performance is what you're after, you might be a very good candidate for a Tri-power setup. My $.02
Burning Brakes
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Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
750 CFM is way too small for a healthy 496. Heck, I'll be installing >900 on my next street 427 currently in the works. That said, if good manners and decent MPG without giving up too awful much performance is what you're after, you might be a very good candidate for a Tri-power setup. My $.02
I swapped out my 780 Holley for an 850, and the difference was very noticeable. I'm just running a fuel sipping 427, but I'd like to bump up the carb size again in the near future.
Thread Starter
Racer
Joined: Apr 2006
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From: Joplin Missouri
So bigger carb is better? I was thinking going down to 650. I have been told by some strip racers that its alot of carb for the street. The reason for the switch is if I'm on the gas it's an awesome ride but I can't drive everywhere at full out. I have those pesky stop signs and traffic. The carb I have could use some going over but it's the end of a project and ill take a straight out of the box solution.
Instructor
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From: Indianapolis, Indiana
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Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
So bigger carb is better? I was thinking going down to 650. I have been told by some strip racers that its alot of carb for the street. The reason for the switch is if I'm on the gas it's an awesome ride but I can't drive everywhere at full out. I have those pesky stop signs and traffic. The carb I have could use some going over but it's the end of a project and ill take a straight out of the box solution.
(Psssst, you can modulate the amount of air that will be going into the engine.)
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Any carburetor you get will still need to be tuned. You may find that the carb you have now would work just fine with a good tune.
Keep the shiny side up!
Scott
Keep the shiny side up!
Scott
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
And, you should definitely tune any carb (but only after the ignition system is 100%).
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
I agree with the above posts: 750 is way too small for that engine, and I can't believe someone actually suggested you drop down to a 650... I'd run at least an 850. The Holley Ultra Series and HP are nice carbs, and QuickFuel, Demon, AED, and ProForm all make some excellent 4150-style double pumper carbs that would suit your application. There is no need for a choke on those carbs if the carb is set up correctly.
It's not that bigger is better. "Correct size" is better, and 750 is too small for your engine. 850 - 900 would be about "correct" for the engine you're running.
There's no such thing. Any carb you buy will need to be properly set up and tuned for your application, along with a correct ignition timing curve.
Lars
It's not that bigger is better. "Correct size" is better, and 750 is too small for your engine. 850 - 900 would be about "correct" for the engine you're running.
There's no such thing. Any carb you buy will need to be properly set up and tuned for your application, along with a correct ignition timing curve.
Lars
Last edited by lars; Nov 18, 2012 at 09:42 PM.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Sounds like it just needs a fine tune. I am running a much larger carb with a ratty cam on a sbc and can sit in traffic anywhere, good manners. Was impressed with AED carbs
If you have adjustable IAB and such that can make the difference between a carb that runs Ok or one that is stellar. Once your motor gets to a certain point its almost mandatory. A factory calibrated carb can only do so much
Last edited by cv67; Nov 19, 2012 at 12:02 AM.
Thread Starter
Racer
Joined: Apr 2006
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From: Joplin Missouri
Thanks everybody for the feedback. So the smaller carb is not a solution. So I can move on from that. Now I'm looking at it from a cost standpoint. If I tune my 750 will I be happy with performance and still be streetable or step up to an 850 which I still have to tune.
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
True. Unfortunately, the more impractical is the amount of torque/power in relation to given traction limits, the more difficult is throttle modulation to finesse. Suggest a "softer" throttle progression might help a little.
And, you should definitely tune any carb (but only after the ignition system is 100%).
And, you should definitely tune any carb (but only after the ignition system is 100%).
Race Director
Joined: Jan 2000
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From: San Jose CA
I think a big problem is that people think "runs fine" means "well-tuned".
You can have an engine that runs 12:1 EVERYWHERE and will run fine. That engine may actually make more power with a leaner curve, and it certainly will get more fuel economy if you can get the cruise AFR leaner. A well-tuned carb will get much better fuel economy, have crisp throttle response, and haul butt.
Most carb manufacturers err on the side of rich, as it will play nice and not likely blow the motor if you throw it on and wind it out.
You can have an engine that runs 12:1 EVERYWHERE and will run fine. That engine may actually make more power with a leaner curve, and it certainly will get more fuel economy if you can get the cruise AFR leaner. A well-tuned carb will get much better fuel economy, have crisp throttle response, and haul butt.
Most carb manufacturers err on the side of rich, as it will play nice and not likely blow the motor if you throw it on and wind it out.
Thread Starter
Racer
Joined: Apr 2006
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From: Joplin Missouri
I managed to get my hands on a Holley 4780 which I believe is an 800 cfm. Didnt cost me anything just traded a friend for some extra parts I had. It does need a rebuild kit but I got one included in the deal. Ive read a few things on the web talking about tuning Holleys. Is there any inside info anyone could give me that would make this job easier. Ive always had electronic controlled cars so Ive never had to mess with tuning unless you count dirtbikes, but that was just one big ****.
Race Director
Joined: Jan 2000
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From: San Jose CA
Even electronic cars can benefit a lot from tuning. GM runs their stock tunes extremely rich during the PE(power enrichment, WOT) tables.
I personally use a wideband and aim for stoich for cruise/idle. For a NA application 12.5-12.8 is generally "good", but it really depends on what your motor wants. An engine dyno or drag strip are the best places to figure that out...
I'm not much up on Holley tuning, but there's probably a million guides out there. Quadrajets make more sense to me.
I personally use a wideband and aim for stoich for cruise/idle. For a NA application 12.5-12.8 is generally "good", but it really depends on what your motor wants. An engine dyno or drag strip are the best places to figure that out...
I'm not much up on Holley tuning, but there's probably a million guides out there. Quadrajets make more sense to me.