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Demon or Holley

 
canadianmudd
I love my Chevy Chevette!
Posts: 3
Joined: 09/07
Posted: 09/18/07 01:08 PM

I am currently looking at purchasing a new carb.  Does anyone have any insight or comments on the two carbs (Demon or Holley)?  What size of carb would you recommend for a Chevy 350 putting out about 440 HP.  Gas mileage does not matter.  

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55Guy
Administrator
Posts: 1153
Joined: 07/06
Posted: 09/19/07 06:53 AM

A good 750 cfm double pumper type carb is what you need. As far as which manufacturer, that's a tough call, both have their advantages/disadvantages.  

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LOVEthoseCHEVYS
V-6 Camaros rule!
Posts: 48
Joined: 09/07
Posted: 12/10/07 11:13 PM

55 Guy is right 750 cfm is a good size. If you go with Holley realize that the bowls because of the way the Holley is shaped with get warped faster but does produce a good carburetor. The Demon describes the way it acts, Demon's are very hard to tune and go out of tune quickly. Also think about edelbrock. Edelbrock makes a 750 double pumper and is easier to tune and will last longer than the other too.  

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geezer1
I love my Chevy Chevette!
Posts: 17
Joined: 12/07
Posted: 12/12/07 11:11 AM

While we are on the subject of carbs. I'm having some tuning problems on my Holley 750 (electric choke,single feed). The two air/fuel mix screw are both barley open, maybe a full turn. If I close either one all the way I know the motor should stumble a stall but it doesn't. I can close them both and the motor will still run, just real bad. At the current setting the motor runs good but there is a bad gas smell from the exaust like its running rich but the plugs all seem ok. Any sugestions would be great. Also, the motor sometimes "runs on" when turning off the ignition.  454, daily driver.  Thanks.  

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55Guy
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Posted: 12/12/07 03:18 PM

Another option is a large Quadrajet from Edelbrock.  

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LOVEthoseCHEVYS
V-6 Camaros rule!
Posts: 48
Joined: 09/07
Posted: 12/12/07 07:06 PM

Hey geezer I have same exact problem with my Nova right now. When I rebuilt the 600 edelbrock on my car now I accidently added in some 750 cfm parts to it, but that is not your problem. Check the float levels. If your floats have dropped it would push in more fuel because the the bowls would fill up to fast so it would dump in more fuel to get the level back to where it is suppose to be. Check those. If it's not them then check the metering rods. If you just don't feel like doing a rebuild if one of those 2 things then I suggest you buy a new carburetor of the same cfm or less. About the running after turning off the ignition system that is dieseling. If the engine is running hot it will continue running that way until it cools it's way down or until you disconntect the ignition system all together. This frequently happens if you have a big motor or high compression. If you have the stock fan try putting on an electric fan it will cool off your engine more efficiently.  

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geezer1
I love my Chevy Chevette!
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Joined: 12/07
Posted: 12/12/07 10:43 PM

Sounds good guys ,thanks.  

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olde_skoole
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Posted: 12/13/07 12:59 PM

you gotta vacuum leak somewhere...  

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69camaro1
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Joined: 06/07
Posted: 12/16/07 08:13 PM

Holley 750 double pumper is perfect. I have heard more complants about demon carbs than any in my life.  

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f370
I love my Chevy Chevette!
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Posted: 12/19/07 02:53 PM

I'm really surprised about the demon carb getting bad reviews here. I ran Holleys for 40 years before purchasing my first Demon carb. My experience has been just the opposite. One thing I have found is that while it's normal when tuning a Holley to go up or down in 3 jet size increments that rule doesn't work with a Demon. You must adjust 1 jet size at a time. Also the DEmon gives you a better fuel to air ratio over all throttle positions. I'll never switch back and currently own cars with both carbs. Blush  

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sds-oe
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Posts: 16
Joined: 12/07
Posted: 12/20/07 09:04 AM

i agree. my street demon ran very good right out of the box. as i fine tuned it, smaller adjustments did more than what i was used to with the 780 holley it replaced.  
it stayed in tune as well.
the fact that the pieces are billet rather than cast, but is comparable in price, makes it an easy decision.  

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