Is a Demon 850 too much carb for a 383?

Posted By: MoparKansas

Is a Demon 850 too much carb for a 383? - 12/30/08 07:18 PM

My brother has 383 that is .030 over, 10.5:1 compression and a 510/292(? - going from memory) hydraulic cam with a stock intake. He can get a decent deal on a Demon 850 carb that is slightly used (about the same price as a new Edelbrock 650). Will that be too much carb for this combo or will he be able to tune it down and make it work?

Posted By: Mr.Yuck

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 07:20 PM

Should be able to tune it down but what's up w/ the stock intake??? get a good dual plane on that thing.

Posted By: rrunner

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 07:56 PM

I would use a 750 D.P. and a different intake.

Posted By: 1E2C

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 08:03 PM

Seems I've heard it's easier to overcarb w/ a Holley than a Carter/E-brock, but I won't have a Holley (never been able to make one work well). Anyway, before the flame wars start, my very mild 383 is running well with an 800 AVS on it, so the airflow capability isn't that much different and he's got a whole lot more cam and compression than I do. So... I guess I'm saying I'd think it should be workable.

: DISCLAIMER : Remember, this from a guy that cannot make any kind of Holley carb run well, period.

Mike

Posted By: AndyF

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 08:15 PM

He'll probably be happier with a smaller carb.

Posted By: lakerism

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 08:17 PM

I have a Demon 750 DP w stock intake and similar cam on my 383 and it runs great.

Posted By: 2boltmain

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 08:18 PM

Smaller carb will need a tweak or two (pump shot, idle misture)- Bigger carbs gonna need some calibrating and trying out. Depends on how much hands on he wants to do.

Posted By: dgc333

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 09:54 PM

Demon carbs are wet flowed so the 850 would compare to a 900 Holley or AVS type carb that is dry flow rated.

I tried a 725 Road Demon on a 360 that is 10.6:1 with a Comp XE268H cam with 509/512 lift and I could never get the engine to run will below 2000 rpm. Ran like stink on the top end but I spend so little time on the top end that low rpm manners are much more important. I tried a bunch of different carbs and settled on a 670 Holley Street Avenger.

I would tell your brother to pass on the 850 Demon. You can likely get it to work but its not going to be the best choice. BG even recommends a 650 for his application.

Its going to take a very talented carb tuner to get decent driveability with the 850 on a relatively mild 383.

Posted By: 1_WILD_RT

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 10:04 PM

This would be my suggestion...

http://cgi.ebay.com/ebaymotors/650CFM-Ho...emZ260331789414

If he wants some other holley, that seller is Holley & they have some great buys in their Ebay store...

I recently bolted one on my stock 383 in my Challenger, OOTB it ran better then any other carb I'd tried & much better than a Edelbrock 750 that had never eally impressed me though I had improved it considerably from when it was new by fattening the jetting..

I wound up jetting the Holley two steps leaner & upping the secondary squirter two sizes...

Posted By: GwaiiEagle

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 10:25 PM

I have 2257 Sealed Power pistons that maybe make 9:1 compression in my 30 over 383 with a Performer RPM and 282S cam.

The 850DP was bolted on with no tweaks and ran fine.

No bog nothing like that, either on the street or at the track. It replaced an Eddy 750 that I really came to hate.

If your bro has that kinda squeeze buy him a better intake for his Bday.

Posted By: gch

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 11:08 PM

It will work but would likely have better throttle response and need less adjusting with a carb more suited to his setup.Things like converter,gear,and driving style should be considered also.I would think an AVS 800 or a 700/750 DP would be better.
A performer rpm would be a nice upgrade before any carb swap.

Posted By: ohiodemon

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 11:20 PM

I'D go with a smaller carb.700-750 cfm.
you'll get better response.
lose that stock intake first.

Posted By: farmington

Re: Is a Demon 850 too much carb for a 383? - 12/30/08 11:56 PM

Buy the 850 and work a trade for a 750 and an intake manifold.

Posted By: dave571

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 02:28 AM

Quote:

My brother has 383 that is .030 over, 10.5:1 compression and a 510/292(? - going from memory) hydraulic cam with a stock intake. He can get a decent deal on a Demon 850 carb that is slightly used (about the same price as a new Edelbrock 650). Will that be too much carb for this combo or will he be able to tune it down and make it work?

As said, I think the 850 is too big.
I ran a 750 mighty demon on my 440. FWIW, I thought I might be under carbed, so I replaced it with a BIGS 950 hp, and it didn't go any faster.

The key here, is what series of demon are we talking about?

An 850 speed demon on this 383 is a complete waste of time. You will hate it.
An 850 mighty demon, will work, but the 750 mighty is a waaayyy better pick

Posted By: 383man

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 05:49 AM

I do agree it can work but a smaller carb would be better on that combo. We run a basic Holley 750 DP on my sons 400 in his Dart and it loves that carb. He tried an 800 DP and a 830 anular DP carb and it was still fastest with the 750. I did do some minor tuning on the 750 but nothing much. It has the best low end with the 750 and has run 11.40's @ 117 with the 750. Unless you are getting it for a very good deal I would try for a 750 DP. Ron

Posted By: Mr.Yuck

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 12:16 PM

Quote:

I do agree it can work but a smaller carb would be better on that combo. We run a basic Holley 750 DP on my sons 400 in his Dart and it loves that carb. He tried an 800 DP and a 830 anular DP carb and it was still fastest with the 750. I did do some minor tuning on the 750 but nothing much. It has the best low end with the 750 and has run 11.40's @ 117 with the 750. Unless you are getting it for a very good deal I would try for a 750 DP. Ron

750DP is probably the best all around carb you can get. It will work on a varity of engines. And it can easily be tuned up if performance goes up.

Posted By: moparkc

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 01:52 PM

I am the not so bright brother who thought bigger is better on the carb, had a 750 edelbrock on this engine and it ran pretty good but needed it for my 70 RRunner. I will take the consensus here and get a Performer RPM intake and a 650-750 carb depending on what I can find reasonably $$. If anyone has interest in BG 850 in great shape with electric choke it is for sale now, please PM me. Do not post much on here as I am not brightest about things, BUT Moparts and its members ROCK.

Posted By: 67_Satellite

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 02:42 PM

Quote:

Buy the 850 and work a trade for a 750 and an intake manifold.

Are you a decent negotiator, because thats what I immediately thought.Someone out there really "needs" that bigger carb., and will be willing to pay to upgrade. You may score a little extra cash or some parts along the way as well.If it's a deal,and you don't need it today,buy and barter.

Posted By: moparkc

Re: Is a Demon 850 too much carb for a 383? - 12/31/08 03:06 PM

I already bought the Demon 850 and tried it. Too much carb for engine. If anyboddy has smaller carb and /or better manifold to trade or would like this carb let me know. thanks

Posted By: HYPER8oSoNic

Re: Is a Demon 850 too much carb for a 383? - 04/18/10 03:58 AM

Quote:

He'll probably be happier with a smaller carb.

100%
Thanks Andy for realizing the driveability factor
in the combo!! Smaller would be better.

Posted By: HYPER8oSoNic

Re: Is a Demon 850 too much carb for a 383? - 04/18/10 04:07 AM

Quote:

My brother has 383 that is .030 over, 10.5:1 compression and a 510/292(? - going from memory) hydraulic cam with a stock intake. He can get a decent deal on a Demon 850 carb that is slightly used (about the same price as a new Edelbrock 650). Will that be too much carb for this combo or will he be able to tune it down and make it work?

One point, if staying with the stock intake go
with the 440 AVS carb (approx 800 cfm), the air
valve is more forgiving to engine mistunes than the Holley. Otherwise a Holley 650 - Demon 670
would get the nod on top of a Eddy RPM manifold,
if hood space permits.

Posted By: forphorty

Re: Is a Demon 850 too much carb for a 383? - 04/18/10 07:56 PM

Hyper8osonic, Where is that Zombie smiley? You sure have resurrectected a few dead threads today.