Speed Demon 650cfm vs. Holley Street Avenger 670cfm - Chevelle Tech
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post #1 of 15 (permalink) Old Oct 26th, 05, 4:36 PM Thread Starter
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Chad
 
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Speed Demon 650cfm vs. Holley Street Avenger 670cfm

(Both electric choke/vacuum secondaries)

My friend is debating which to go with, the speed demon comes in at $400 bucks which is a lot more to spend over the Holley but is it worth it? Will the Holley give the same performance as the demon? The engine is basically a stock 396 with nothing changed but the intake, headers, and hei.

Chad - 1972 Chevelle SS
- 350
- Trick Flow 62cc Heads
- RPM Intake, Speed Demon 650 VC/EC
- Voodoo 276, Hooker 1 5/8 Headers
- Muncie m20, 3.73's + posi coming soon to appease that cam..
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post #2 of 15 (permalink) Old Oct 26th, 05, 5:44 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

I have used several Demons and have found them to be great quality and easy to tune and use. Somthing to keep in mind is the type of Demon you choose... even the same cfm can have differant charictoristics. For example I used a Speed Demon 650 with elec choke and it was ok, but changing to the Mighty Demon (dp) 650 netted an increase in power as well as throttle responce based on my cam/head/intake combination. The bottom line is Holley and Barry Grant make great products, I just feel the Demon is better quality... especially in the higher end models.
If I were you I would call Barry Grant's tech department and give them the information on the engine.. cam duration at 050, lift, intake you plan to use, ignition, and what type of driving you plan to do with it. They have always been helpful to me and as they say "the only dumb question is the one not asked".

Steve

Track Manager, Redding Drag Strip. My Street/Strip 65 Chevelle 1/4 Mile:11.61@116.03MPH with a.0221 reaction and a 1.603 60ft MY: album http://community.webshots.com/user/steves65
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post #3 of 15 (permalink) Old Oct 26th, 05, 6:02 PM Thread Starter
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Chad
 
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

See there doens't seem to be a defining difference other than price, It seems to be very debateable, which is disturbing when you are comparing such a huge price difference.

Chad - 1972 Chevelle SS
- 350
- Trick Flow 62cc Heads
- RPM Intake, Speed Demon 650 VC/EC
- Voodoo 276, Hooker 1 5/8 Headers
- Muncie m20, 3.73's + posi coming soon to appease that cam..
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post #4 of 15 (permalink) Old Oct 26th, 05, 6:45 PM
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Joe
 
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

Have a 670 Avenger on my 408 motor not. Motor has a hyd roller cam, head work, etc., etc.. For a roce oriented car I would go different, for a 99% street cruiser I think the 670 works well on a 400CI motor.
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post #5 of 15 (permalink) Old Oct 27th, 05, 8:37 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

If you sit a Holley and a Demon on a bench, side by side, and compare the two, there will be no doubt as to which one is better built. Ditto on the suggestion about calling Barry Grant tech to get their recommendation, they will not lead you wrong!!
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post #6 of 15 (permalink) Old Oct 27th, 05, 10:56 PM
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Mark
 
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Thumbs up Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

I have the 670 Holley on my 350 Camaro motor. It is very reliable and runs great on the street. I have a mild cam, and +.30 bore, headers and a performer intake. I would go with the Holley and put the money into something else on the project.

The Golden Rule : He who has the gold makes the rules.

1969 Chevelle Malibu 454 TH400 3:55 12 bolt (purchased new by my Grandfather, originally a 250 c.i. Powerglide)
1969 Camaro x55 SS350 4 Speed 3:73 12 bolt (Z28 stripes)
1969 Corvette 4 speed (wanted to help complete the Chevy lineup that year)
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post #7 of 15 (permalink) Old Oct 27th, 05, 11:46 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

it seems sentiments have changed, yous to be everybody say demons were junk. cont be tuned, machining junk in them etc. my first demon was a mighty demon after 20 years of holley. i'll never go back. some ' including local dyno they wont come out of the 60 and realize you can improve on somthing. i thing it because they have that gaint air bleed box for holley and i can buy a couple undrill and make my own for 1/20th the price.
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post #8 of 15 (permalink) Old Oct 28th, 05, 6:52 AM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

unless BG has cured their quality control there's no way i'd ever use anything but a Holley. i have a few buddys who did not get very good customer service with BG and some of the junk they used to put out. so that's also something to consider. personally i don't know anyone who has been happier with BG products than Holley products. maybe times are changing, i don't know.
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post #9 of 15 (permalink) Old Oct 28th, 05, 8:06 AM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

I think you will be happy with either because I have heard alot of good things on both of these specific carbs. Price wise, I think it's only about $40 difference. I run a Road Demon with electric choke and love it but would not hesitate to get a Street Avenger. I do like the fact that I can polish the all billet Demon where as the Holley gets cruddy after the first year or so.

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355/350 w/3:73's and Posi
Performer RPM , Road Demon 625
XE262, Hooker Super Comps (#2808)
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post #10 of 15 (permalink) Old Nov 11th, 05, 9:48 AM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

The two carburetors are very similar. Going mail order the Demon is going to be about $50 more expensive than the Holley. The Demon will have Billet Metering Blocks, and a Billet baseplate vs. the cast ones on the Holley. Also the Demon will have 4 corner idle circuits vs. 2 corner idle. As far as performance the Demon will atomize the fuel better giving better throttle response, acceleration, and drivability.

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post #11 of 15 (permalink) Old Nov 11th, 05, 10:18 AM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

I am running a Speed Demon 650cfm on my fairly built 350. This is a great carb and well worth the few extra bucks over the Holley.......looks good, easy to tune, very good throttle response....
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post #12 of 15 (permalink) Old Nov 11th, 05, 12:55 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

With a 396 I would just buy a 3310 750 Holley
$200 from Scoggin-Dickey

..a $400 650 cfm carb on a stock/mild 396 is really unnecessary.
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post #13 of 15 (permalink) Old Nov 11th, 05, 5:21 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

I had the 670 street avenger and it really never ran just right no matter how much it was played around with. I put on a 650 speed demon it started better and didnt have the off idle stumble i had. Throttle response was better also. This was out of the box with no tuning all i did was kick the idle speed down about 400rpm. The Demon deosnt come with the cheesy cheap looking plastic like the holley does.
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post #14 of 15 (permalink) Old Nov 11th, 05, 10:31 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

Have you ever considered a Good Ole Q-Jet? I think they have gotten a bad rap from folks who didn't know how to tune em.

I've always perfered them to any Holley I have ever run.
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post #15 of 15 (permalink) Old Nov 11th, 05, 11:32 PM
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Re: Speed Demon 650cfm vs. Holley Street Avenger 670cfm

It's hard to beat a good Qjet. There's one or two shops that specialize. I have a qjet. It's great.

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