Serious problem with a new 825 Mighty Demon

I replaced the 750 Speed Demon with a step bigger 825 Mighty Demon in my 393. The problem is that now the engine wont "idle" below 4000 rpm. There is so much fuel coming from the primary boosters that the throttle must be kept open.Engine wont run smoothly below 4000 and wont run at all below 2500-3000 rpm.
Fuel level is set correct ( various levels tried) , basically it is at the bottom of the sight glass. Throttle positions are correct( a square is visible from primary side transfer slot.
I disasembled the carb and only thing I found was the boosters, both primary+secondary are slightly loose, they can be moved back/forth by a distance of 1/20" or so maximum.
The engine in the Futura is leaned backwards( rear of the engine sits lower than the front) so I thought the fuel level the metering block sees is higher than the sight glass tells, so I jacked up the rear of the car to make the car level.No change.
I then changed the carb and installed a box stock 750 vacuum Holley. No problem, engine runs smoothly, idles at 800 rpm and , get this, feels more responsive than the 750 DP Demon I had in the car earlier. And feels to be making just as much power at 6000-7000 rpm as the 750 Demon.I was really surprised to encounter this good performance from this " industrial engine carburetor"...Hey, even blew the doors of a 560 hp 468 ci Camaro the other day...
Is this a typical fault in the Demons ? Has enybody else had a similar problem?
[addsig]

I have had a similar problem with a barry grant carburetor 850 cfm. found the problem to be the power valve and bowl gaskets not sealing correctly. replaced the gaskets and retorqued the bowl screws and power valve and have not had a problem since.

sorry about your demon carb trouble, but it sounds like you may have found something better with the holley. Just a thought ,
11.05 times with the demon carb may turn into 10's with a good holley. Let us know.[img]/phpBB/images/smiles/icon_confused.gif[/img]
[addsig]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2005-05-29 17:10, mtorb wrote:
I have had a similar problem with a barry grant carburetor 850 cfm. found the problem to be the power valve and bowl gaskets not sealing correctly. replaced the gaskets and retorqued the bowl screws and power valve and have not had a problem since.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>

I had same powervalve problem with 600cfm holley which I was cleaning/inspecting for my friend. Power valve had quite thick gasket and I replaced it with little less thick gasket. Pv went nicely back but when testing carb fuel flooded from boosters.. Powervalve threads were too short for slimmer gasket and fuel escaped under gasket.. [img]/phpBB/images/smiles/icon_rolleyes.gif[/img]

Thanks for the hint ! I´ll check the PV+ gaskets.
[addsig]

I'd check every orrifice including behind the jets. I have a new 750 Mighty Demon, and it some big alloy filing behing the main jets, new out of the box. It sounds like you have no idle/intermediate circuit at all. Get a WD40 spray with the plastic tube nozzle and blow out every hole in the metreing blocks, and make sure all idle airbleeds are clear when the metering blocks are off the carby.
Better still, get it replaced with another under waranty.

I took the carb completely apart today. The primary metering block had a lot of small aluminum shavings in the orifices.It looked like it had not been cleaned after drilling. I cleaned the whole carb completely with solvent+ compressed air.All the orifices look clean now and no aluminum pieces could be blown out anymore..Unfortunately no big change in the performance. It was a bit better now, could make the engine idle at 2300 rpm lowest, but could still hear it was running poorly.Extra fuel is still coming from the primary boosters.
Power valve is a 6,5" unit and I have normally around 9" of vacuum at idle. The primary jets are 76s. Power valve is not blown and absolutely eveything looks ok in the carb.
I was wondering whether I could swap the pimary and secondary metering blocks to see if there´s any difference, also thought trying with a blocked power valve but dont know whether that really could make such a big difference.
I must say I am very confused.[img]/phpBB/images/smiles/icon_confused.gif[/img][img]/phpBB/images/smiles/icon_cry.gif[/img][img]/phpBB/images/smiles/icon_bicker.gif[/img]
[addsig]

call demon if its brand new

Thats not the first time I've heard of quality problems with a BG carb. You need to get in touch with them and make them make it right.
[addsig]