I got the BG 750 the other day to replace The 670 Street Aveng. thats on the engine now.

Its a beautiful Carb. The Castings are impeccable and Im sure it will match up with my 383 just fine. BUT..I got to say there were a Few eyeopeners when I started to set it Up.

When I took it out of the Box It had a Tag hand Marked with flow numbers ect. But the Line for the Testers Signature Was Blank..I doubt it was even tested..someone just filled in some nice numbers I think.

Then the elec. choke had to be Modified so My Air cleaner would Clear the Choke pull rod. No Big deal, BG instructions said this would be Likely because the choke tower casting overlapes all the way out onto the base for the aircleaner.

Next, The Float Bowls have a Plastic part that acts as a anti splash piece, The one in the Primary Bowl was Smashed..It got Smashed before the Bowl was installed and the assembler went ahead and put it on anyway,Damn .

Most Important, the Primary Butterflies Dont close up in the Bore equally. Off by about .020" . So Its not possible to make the Initial adjustments for the carb until both Butterflies sit in there equal like it should have been fitted at Barry Grant. The Secondary side was Perfect.

Also FYI The duel inlet wont accept the Holley dual feed Line. Holley uses 7/8-20 in, This Carb has a 9/16 -24 fitting inlet. No adaptor options..Have to Get The BG Fuel Line.

Anyhow The Carb will Work out fine, But I want to say I dont think Barry Grant Has any Quality control in place at their assembly line. Also I had heard Summit doesnt offer Barry Grant Carbs for sale anymore. I knew that before, But now I think I know More Why :laughing:

 

I have the same setup, BG 750 Demon on a 383. PM me sometime. Mine was installed by Ed Gaunt and works good for me so far. I have terrible fuel econ but the car seems to drive and has pleeenty of gop-time when you want it.

 

I dorked with my 750 speed Demon for about 4 years. I was not 100% satisfied. So i took it to a race carb shop and invested about $300 into air bleeds/flow bench/dyno tuning on a test mule motor.

I'm now 4 jet sizes smaller on the primaries and three on the secondaries and it runs great. Out on the road racing track I have been very abusive to my Vette and the carb has not even hickuped

 

IMHO BG has terrible quality control, the first Mighty Demon 750 I got was a mess. After a few trips back to BG and some modifications it is a good reliable carb, but what a PITA.

A carb has to be setup for the motor its on or it will never run "right", take the time to set it up and tune it and it'll run good. You will probably find that the idle circuit is incredibly rich (probably the cause of your terrible mileage karioth). I had to reduce the idle feed restrictor size a fair bit to get cruise throttle AF ratios and idle ratios reasonable. Cruising at an AF of 11:1-12:1 is wasting a ton of gas, but if that's your thing I had a 1050 3 circuit dominator on the car that ran great but would cruise at an AF of 10.7:1.. LOL

As it sits I get a cruise AF of 13.7-14.3:1 and a flat AF of 12.5:1 at WOT.

Good luck, be prepared to get your hands gassy..

 

i like mine....gas mileage is non existent though...but lots of smiles per mile

 

mine is an 850 mighty demon tuned specifically on my 406 engine by american speed of ill...the carb has plenty of grunt and even in a racing application has been been a good boy up to now...but consumption is simply outrageous!