I have a 67 396 Perf RPM mainifold Perf RPM Cam, and am thinking of getting the 850 mighty demon.Now I have a holley 3310 vaccum sec. What is your thoughts on this carb??

If its one of those try it before you buy it deals, I'd give it a try. I don't think I'd shell out the money for it,probably runs better with the 3310.

IMO, an 850 Demon is too big for your 396.
Check out the Barry Grant website for recommendations...
If I recall correctly, BG recommends 500+ cubes for their 850. Those BG carb flows are rated a different way than Holleys.

DS67SS, I could sell you my Speed Demon 850 Mech. Sec. if you are interested. It only has about 100 miles on it.

Demon's are awesome carbs!! Or talk to the tech guys at Barry Grant, they say if you have enough duration you can run a bigger carb like the 850. Of course there are other variables as well.

I am interested in one because the vaccum secondarys dont seem as reliable? Im not racing but think it may help with accelaration.The cam is edelbrock performer RPM 240/246 560/573 lift.
Do you think it may be too much fuel?

After reading the BG website they recommend a 750 Speed Demon for my engine size and type.Im not real worried about mileage as much as performance.

Originally posted by chevydog66:
Demon's are awesome carbs!! Or talk to the tech guys at Barry Grant, they say if you have enough duration you can run a bigger carb like the 850. Of course there are other variables as well. =
I agree they are great carbs, I have had good results with them but,,,
They actually told you to run a bigger carb with more duration???
Gotta love tech lines :D
Now if you have enough duration & are spinning the engine to 8500, I might agree but sticking a big carb on because you have a big cam seems a bit counterproductive to me, what was their reasoning for this :confused:

DS,
I agree with Bill, I think the 850 Demon is to big for a mild 396.
I would look at no more than the 750 Demon if that is what you want & even it is on the large side but should work quite well.
A vacuum secondary should not have a reliabilty problem. They are excellent carbs when you get the spring right & are much more forgiving if the carb is on the large side.
I think you will find a lot of folks on here running them with very good results.

get yourself a 750 HP Holley..........if your not concerned about mileage.....forget the BG stuff

I would try to borrow something and try it before spending the $$$. My old 396 picked up a tenth when I switched from a 750 double pumper to a 780 vacuum secondary. The 750 had all the candy, thinned shafts, blades, flowed, etc. The 780 only had the choke milled.

Well I am glad I asked.I just want my car to run at its best.If an 850 is too big then maybe I will just keep this 750? I just may look for a mech secondary.

DS67SS,

On your combination we'd recommend using a 750 Mighty Demon carburetor. This will give you the mechanical secondaries, and increased air flow you're looking for while maintaining the air velocity, acceleration, and performance.