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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> 770 Holley street avenger or 750 BG Street Demon
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Topic Review (Newest First)
04-03-2004 08:23 AM
jamnut I would call Barry Grant and ask them what carburetor they recommend for the application. I know that they make Demon's specifically tuned for certain crate motors like the ZZ4. So they might have one that's already tuned for your motor.

By the way, I'm running a 750 speed demon on my 383 in my Elcamino, but when I went to a higher duration cam we actually had to modify the carb to basically what a Mighty Demon is out of the box. So as I stated above, call Barry Grant for your application.

Basically a Road Demon is for a lightly modified engine.

A speed Demon is good for up to about 236 duration @ 0.50.

A Mighty Demon picks up where the Speed Demon leaves off. And then there are the race Demons

The only complaints that I've heard about Demon carbs are from people that didn't research the carb that they bought to make sure that it would work for their application.
04-03-2004 02:33 AM
LilSmoke Since I bought a 625 road demon for a hot street 355 in a vette I built for a guy,I have nothing but praise for em. Once the carb is tuned for the application,it is more than any holley has ever been.

I started modifying holleys in 1971,and even though Ive never seen anything hard about em,they always were just a tad off as far as precision was concerned. Back in those days,you either bought a Braswell or you did it yourself including a homemade flow bench powered by a shop vac. Probably wasnt as accurated as a bought one but it did give u a tool to learn by.

Next wk I am going to buy a 750 race demon for a 357 flt tappet roundy engine that will be running at approximately 3500 to 5500 density alt. We will see how bad I screwed up,but I dont think so!
Especially with the adjustable air and fuel bleeds.
04-03-2004 01:24 AM
Jared hey if you have enough time to get the porosity out of my holley metering blocks ive got a few to send you. Demon parts impress me a lot more than holley.
04-02-2004 08:00 AM
johnsongrass1 Demon simply build carbs that hold better tolerances than factory stuff(Holley). Holley does make after market stuff but Holley still holds them to the a degraded "good enough" spec. That's part of why they are less expensive. Demon's cost more but they still flow something near their rating. It's a loose term I know. You can spend half the money on a Holley and do the tolerance work yourself in about three hours work. I've got more time than money.
04-01-2004 10:19 PM
Jared Im running a 650 speed demon on my 355 (350-400 hp). when i installed it the thing barely idled let alone ran, they flow more like a holley 750 and have jets to match. if you go with a demon go with the 650 speed demon or maybe smaller yet. My demon has the quick change spring pod on it also, if that is what you are talking about. I also have a holley 750 and the demon will run the thing into the ground any day. as stated the demons are built much better than the holleys too. 4 corner idle is nice to have also. just my .02 good luck.
04-01-2004 07:06 AM
johnsongrass1 I would find a used Holley 750 and do the reworking to flow 830.
Cheap yet still effective.
04-01-2004 06:36 AM
jameskirk1 Having running both brands of carb, I would reccomend the Demon...They are MUCH more precise in all adjustments, and flow more cfm than their rating...Plus, most all "standard" Holley speed parts will interchange onto them...You can get the adjustable secondary pod from Demon as well...Just my .02

04-01-2004 06:34 AM
stepside454 If it were me Id use a 650 CFM Carb on that motor. that motor makes 380 HP @ 5500 out of the crate, no need to take it past 6000RPMS for sure. 650 would be more than adaquete. John
04-01-2004 06:30 AM
Shawn Horan
770 Holley street avenger or 750 BG Street Demon

Looking for a carb to put on a 360 380 mopar performance magnum crate motor. Both carbs are about the same amount of money (Holley $395 vs. Demons $399)., but which would work best for a street driven vehicle, which will see the track once in a while. I'm kinda leaning towards the Holley (adjustable vaccum secondaries sounds like a good deal,plus 770 cfm.) I'd put all the details about both carbs but, i'm kinda in a hurry. I've never used a Barry Grant carb so my knowledge about them is limited. This isn't my engine but a friend who has the basic know how when it comes to engines. Once this carb (which ever that may be) is set up it will most likely stay that way.I know there are die hard Barry Grant as well as Holley guys out there, so lets kept it to a civilized discusion.

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