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Old 04-06-2012, 06:58 AM
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Carb choice

I am looking to purchase a new carb for my car and looking for suggestions and things I should consider. Here are the specs on car;

74 GMC Sprint
454 bbc
3;08 rear gears
Holley manifold not sure of model
Has Edlebrock 1405-manual choke, should I consider elec choke on next carb?

Looking for economy as now it gets terrible mileage, 8-10 in town maybe, and 10-11 on intersate at 60-65 mph.

Thanks in advance for your suggestions

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Old 04-06-2012, 08:31 AM
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Fix the 1405.
There is no such thing as buying a universal carb, bolting it on an engine and having it run perfect. Theres alot more to it than the idle mixture screws.
I always spend a day rejetting and adjusting and that time costs more than a new carb.
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Old 04-06-2012, 09:35 AM
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I agree, fix the 1405 carb.

If it is properly tuned for idle, part throttle and WOT so that you have proper air/fuel mixture throughout the operating range that is the best you are going to do for gas milage as far as carbs go (ie changing to a different carb won't improve your milage).

Your mpg does seem low, unless you have a very high performance build on your 454; but the bbc is not an economy engine so don't expect to get much better than about 15/18mpg, which is about what I got with my El Camino running a 305sb with 373 gears.

Check your plugs, if they show you are running rich, that would be a big factor on milage - if so then you need to tune the carb.
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Old 04-06-2012, 12:08 PM
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Then only other suggestion I would make would be to consider a Q-jet from a carb builder like Jet. They can put together a carb that will be pretty good right out of the box. A Q-jet has the best potential for maximum fuel mileage and they work great when built and tuned for a specific engine.
The Q-jets from Edelbrock worked real well but I think they are all gone now.
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Old 04-06-2012, 07:19 PM
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The Quadrajet is a good idea if it will fit your Holley manifold. If you have to change manifolds, and economy's your game, you have to factor that in.

If economy is your game, though, I suspect you're better off optimizing your current setup than spending dinero on a new carb. There's no magic bullet; you've got four hundred and fifty four cubes to feed. You can spend lots of money on carburetors and you'll never change the basic facts. I don't think any carb is going to make a huge difference. Say the spreadbore gains you 20 percent. You shoot up to 12 MPG from 10. How long is it going to take to get the money back on your new craigslist carb, rebuild kit, and manifold?

Definitely get the electric choke kit (you don't need a whole new carb for that) if you're not in the habit of remembering things like shutting off manual chokes. Which includes me. But I live in Tejas where you can initiate internal combustion most of the year without bothering about things like chokes. I haven't consulted mapquest, but if the "No" before "Hutchinson Island" means what I think it does, you may not get away with what I can.

If you get bummed out about the price of gas, ask your neighbor with the Prius what he spends per month on gas plus new car payments. Maybe you'll feel better about your 10 or so MPG.
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