TT I WISH I was putting those on! That's the BBC oval port IDF model, but $3600 for a manifold and carb is a little much for me! I got the picture from here if anyone is interested in those

 

I don't defend any company because I've been screwed by a major cam company and an aluminum head manufacturer.

But what diaphram are you refering to on the Demon. They only have the two reusable gaskets from the bowl-metering block-to main body.

IMO- I believe that any carb can be tuned to work. I've had all kinds over the years. It's just a learning curve. I think that q-jet, Edelbrock/weber/carter, holley, and Demon are wonderful carbs. I can tell you that a booster change is not going to solve not running under 2000 rpm. I would be checking for a vacuum leak on that 850

I will also say that I'm a firm believer in sub 5 psi fuel feeds and the use of the biggest needle and seats. I also have never primed a fuel bowl. That's what the starter or fuel pump switch is for.

 

I had a BG Might Demon (650) that worked perfect right out of the box on my well built 355. Great idle and amazing throttle response. To me, quality was far superior to the prior to Holley's I had. My engine builder uses BG carbs on many motors he dynos with excellent results. I will be purchasing another BG carb for the 406 he is building now.

 

My take is that Barry Grant has a quality control issue. The carbs are good but probably too many assemblers smoking rope on the midnight shift.

Others have learned the first thing you do is take the bowls off and look for anything that is not tight and metal particles. Then put it back together and you will be fine. I know this isn't right but not that hard to do, not any more work than changing jets

 

take a look at the ebay auction I posted...just 400 for the manifold

 

There are a lot of tuning variables on any carb that can affect how "crisply" the carb responds. Timing and timing curve setup is also of critical importance. I can't cover all the possible variables, but I can comment on your Demon carb issues...

I happen to like the Demon carbs, but I recognize that BG seems to have their share of quality control problems. I have seen Demon carbs new out of the box actually missing gaskets and seals, yet they have a nice "wet flow tested" certification tag affixed to them. The guy doing the wet testing must wear a raincoat. I have also seen the BG carbs with defective linkage pieces, loose parts, porous castings (causing severe flooding), incorrect setups, and one that came out of the box with no jets installed on the primary side (it ran a touch rich upon initial startup...). On the Tuning for Beer Tour in Northern Virginia, we tore down a new BG carbs and found steel slugs from the foundry in the primary float bowl. For this reason, I've had a lot of people buying BG carbs drop ship the carbs to me for setup and testing directly from JEG's (previously from Summit), and I actually test run every BG carb that the European guys order before I ever ship them overseas. The service and warranty department at BG is marginal at best: BG would not honor a warranty on porous parts found in a new carb, but gave me the part number so I could buy a new bare bowl. The Tech line cannot be reached on most occasions, and when you do get through, it's like talking to a high school auto tech class student. BG answers their tech request e-mail in about 3 days, if they answer at all. So you're on your own if you buy one of these carbs... Once set up and tuned, they run exceptionally well, but be prepared to do some tinkering. I completely tear down every new BG carb prior to ever firing it up. Be sure to check out and read my BG installation paper and my BG setup paper if you buy one of these carbs - for a copy, send e-mail request to:
V8FastCars@msn.com
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