Demon carbs. Whats your opinion?

[BADPURPLE70CHEVY]

Got a chance to buy a 750 dual line demon carb for 200.00 dollars that is supposed to be only ran 2 months. Whats everyones take on these carbs. It will go on my 406. It should be big enough for the motor. Post pics if you have any also. I want to see how they look on your motors. thnx

[LEEVON]

I'm a demon convert (carbs that is). They are very simple, solid and adjustable. Lots of folks don't like them because they aren't "straight out of the box" carbs. Most of the parts are interchangeable with Holley (cheap) and they can be easily rebuilt.

Do you know which model 750 you are looking at? Is it a double pumper, vacuum or mechanical secondary? How much cam (duration and lift) are you running? One thing to keep in mind is that these carbs flow much higher than advertised. Bigger is not better. You will have alot of tuning headaches, not to mention a rich idle circuit if it's too big. My experience with a big cammed 350 was that a 725 was too big. I sold it and bought a 650.

For $200 you can't go wrong though. If it's not the right application, throw a rebuild kit in it, and sell it for more and get the right one. These regularly sell for $300 on the low end for street carbs and much more for racing models.

[LockDoc]

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There are a couple of opinions in this thread. Like 4 pages worth..

http://67-72chevytrucks.com/vboard/s...mon+carbs+junk

LockDoc

[BADPURPLE70CHEVY]

Any more opinions,problems,quality?

[RoadDevil13]

All Barry Grant carbs are great.....Demons are awesome, wish I could afford the Jr for my 72

One should always keep in mind that anyone above sea level will likely have adjustments to make and that NO carb is ever truly a "bolt on and go"

[Ackattack]

I saw this the other day in a magazine.....thought it was bada$$

[RoadDevil13]

Originally Posted by Ackattack

I saw this the other day in a magazine.....thought it was bada$$

yep...that is a real nice setup, all the insides are fully interchangeable so you can really dial those in, but they arent cheap.

(interchangeable venturi sleeves, airflow ratings are available from around 500 to over 1000 cfm)

[shocker]

when buying a demon, always buy a one size smaller cfm than any other holley, the biggest downfall to these carbs is you cannot get them lean at idle. they work great on big cam motors but on a 300hp small block there are way better alternatives

[dznucks]

I have a holley, a demon, and an edelbrock.

When i first bought the demon to replace the holley, i could never get it to run right. it cruised fine and WOT was awsome, but the transitions from idle to cruise to part throttle to WOT sucked to say the least. i was and am no carb expert and I knew it was not tuned right and the edlebrock was cheaper than having someone tune it.

After having the edelbrock, finally understanding carbs, and getting a A/F gauge, just last weekend i decided to rebuild the demon and give it another go. The carb is a 625 electric choke, vacuum secondary. i bought it new and ran it for maybe 6 months on my DD before i got sick of it.

when i opened it up i found aluminum shavings everywhere. needless to say there was no deburring after the machining operations. both my primary idle feed restirctor channels where blocked with shavings and the full manifold vacuum port was completely blocked with the sealant they use to bond the brass vacuum tubes to the baseplate. In addition, the screw that holds down the small accel pump squirter was a solid screw. it is supposed to be drilled in the middle and have a channel for the fuel flow from the accel pump to pass through. That fully explains why transitions were crap and these are all problems that came from the manufacturer.

I have heard nothing but good things from well tuned demon carbs and experienced nothing but headaches from mine. I hope i can get mine running as good as people say they are capable of running. if there are any demon tuning experts, i have questions.

That being said, i dont want to disourage you from getting a Demon but i am strongly suggesting you rebuilt/deburr it, new or used. they are very simple once you open them up and a rebuild on a new or gently used one will be a piece of cake. Also dont get too big of one either. the 750 will be too big for a mild 350.

[Tech @ BG]

Originally Posted by dznucks

I have a holley, a demon, and an edelbrock.

When i first bought the demon to replace the holley, i could never get it to run right. it cruised fine and WOT was awsome, but the transitions from idle to cruise to part throttle to WOT sucked to say the least. i was and am no carb expert and I knew it was not tuned right and the edlebrock was cheaper than having someone tune it.

After having the edelbrock, finally understanding carbs, and getting a A/F gauge, just last weekend i decided to rebuild the demon and give it another go. The carb is a 625 electric choke, vacuum secondary. i bought it new and ran it for maybe 6 months on my DD before i got sick of it.

when i opened it up i found aluminum shavings everywhere. needless to say there was no deburring after the machining operations. both my primary idle feed restirctor channels where blocked with shavings and the full manifold vacuum port was completely blocked with the sealant they use to bond the brass vacuum tubes to the baseplate. In addition, the screw that holds down the small accel pump squirter was a solid screw. it is supposed to be drilled in the middle and have a channel for the fuel flow from the accel pump to pass through. That fully explains why transitions were crap and these are all problems that came from the manufacturer.

I have heard nothing but good things from well tuned demon carbs and experienced nothing but headaches from mine. I hope i can get mine running as good as people say they are capable of running. if there are any demon tuning experts, i have questions.

That being said, i dont want to disourage you from getting a Demon but i am strongly suggesting you rebuilt/deburr it, new or used. they are very simple once you open them up and a rebuild on a new or gently used one will be a piece of cake. Also dont get too big of one either. the 750 will be too big for a mild 350.

The standard squirter used on the majority of the Demons is just that.. a standard one with no slot or holes. The other screw used in applications where the squirters are 42 and larger would be the hollow screw which has the hole and slot but is not standard on the carburetor you referenced.

[BADPURPLE70CHEVY]

Cam specs

INT EXH
ADV DUR 268 274
DUR@ .050 230 236
VALVE LIFT .552 .564

With the dart heads and other performance goodies and balanced and blue printed the engine builder i know said he ran the numbers and the motor should produce 500 to 550 at the fly wheel. Is this 750 double pumper enough or not?

[68Stepbed]

That 750 may work rather well on your 406. I had a 625 RD Jr. and had some of the same issues as dznucks had. Once it was past the idle circuits, it ran like a, well, a demon. The idle was terrible and extremely rich and the transition from idle was bad. I'm also in the same situation as dznucks as I was very inexperienced and knew nothing of carbs. Knowing what I know now, I could've made it run alot better.

For $200, I would jump all over it. Even if you have to work on it or rebuild it, it's worth the money. We're not too far away from each other. I could help you with it if you could make it over here. I would come to you, but I would end up needing a tool or two that I left here.

[BADPURPLE70CHEVY]

Originally Posted by 68Stepbed

That 750 may work rather well on your 406. I had a 625 RD Jr. and had some of the same issues as dznucks had. Once it was past the idle circuits, it ran like a, well, a demon. The idle was terrible and extremely rich and the transition from idle was bad. I'm also in the same situation as dznucks as I was very inexperienced and knew nothing of carbs. Knowing what I know now, I could've made it run alot better.

For $200, I would jump all over it. Even if you have to work on it or rebuild it, it's worth the money. We're not too far away from each other. I could help you with it if you could make it over here. I would come to you, but I would end up needing a tool or two that I left here.

Thanks for the offer. If i buy it i will let you know if i get stuck. By the way your bible sig at the bottom tells me you are a true christian because you are not ashamed. GOD BLESS YOU.

[fastom]

I have run Demon carbs on my car with a 383 and now my truck with a 383. They work great and don't have the leaking problems like the Holly's I've run before.

[lumpy81]

I ran one for a few years and I don't have anything bad to say about it. After some tuning I could tell I wasn't going to be going back to my Holley any time soon.

[hotrod 80]

I bought a used 650 and freshed it up . After a day on the dyno with a broad band the shop owner said he wishes he could get fuel curves like i had from fuel injection . I like Demon carbs and have never had any problems

[Tech @ BG]

The 750 may be a little big on the 406 but for the price you have some room to work with. A couple of options with the first being to use it in conjunction with a 1 inch 4 hole spacer. The other option is to send us just the main body and have the boosters changed over to annulars which will make it smaller but it will have the performance of the larger carb on your combination.

[BADPURPLE70CHEVY]

Originally Posted by Tech @ BG

The 750 may be a little big on the 406 but for the price you have some room to work with. A couple of options with the first being to use it in conjunction with a 1 inch 4 hole spacer. The other option is to send us just the main body and have the boosters changed over to annulars which will make it smaller but it will have the performance of the larger carb on your combination.

Thanks

[Tech @ BG]

Also make sure it is a 750 by looking at the number or numbers on top next to the secondary vent tube on the main body. Does it have a choke horn ? A 750 Speed Demon will have a 7 there and a 750 Mighty will have a 40.

[LEEVON]

Great job Tech @ BG!

[57larry]

I bought a new one, couldn't get it to run right, took car & carb to local carb shop, they said it was a piece of crap, call Berry Grant tech line 2 x's got a wise guy both times. sold cab. I'll never buy another