OK, I am back on for a new carb. I am going from an auto to a 5speed, and it sounds generally the right thing to do. I have zeroed in on a Barry Grant Mighty Demon. That's what I want (don't confuse me with facts about other brands or models :clonk:). I have talked to the BG guys, who have been great, but I am waffling on 750 vs 800. Here is the set up, which will be used for driving to the burger stand and car shows, it never will see a drag strip....

-468, 9.5:1
-820 heads, mildly pocket ported and cleaned up
-245/235 @ .050, .550/.550
-Rhoads lifters
-Edelbrock Performer RPM manifold
-MSD Digital 6 with 6000 rpm limit
-Hooker Comps, Flowmaster dual, cross over, and Pypes Violators
-TKO600, 3.73 (mathematically equivalent to 4.28 w/ M22)
-4,200' elevation

The BG guys say that 800 is best ultimate HP choice, but the 750 could be crisper and more driveable. I want crisp and the best shot at tuning out the off-idle bog that I had with my 770 Avenger. They say that the annular configuration will help. But since it's annular, it isn't apples to apples flow for the size designation. Makes it confusing to a simple mind like I have.

Anyone have any last minute thoughts on 750 vs 800? As I said, the BG guys have been great to talk me through stuff, a much better experience than I had previously with the other carb. I just like second opinions. Again, please no carb manufacturer commentary, it's just about size.

750, we ran one on a 468 with 11:1 compression with an ultradyne hyd cam

288/296 @.020 231/239 @.050 .550/.575 110° lobe center

Your a little bigger on your cam but i think the 750 would be just fine, make sure if you go race demon you get the GC tune-up

Another example, A customer wanted a 502, he ordered the semi together one, we assembled it. It cam with a 850 holley, he also had a 750 silver claw bary grant {close to the mighty demon and race demon} that we put our tune-up on when he had a 402 in the car, i cant remember the exact numbers but the BG 750 went quicker than the 850 holley that came with the engine package

I grabbed this from another thread, posted by the BG techguy....

"Doug, our carburetors do flow more than most of the advertised rating numbers. A lot of the numbers are a commonly familiar number such as 650 , 750 , and 850. Take for example our 750, it is a 1.402 venturi and 1 11/16 butterfly which is commonly know to be a 750. Due to our patented air entry design [much like when we used to hand port the other carbs] they flow more with the 750's flowing a little over 900 wet.The dry flow number would be even higher."

I talked to BG about this. The Mighty's annular boosters apparently impede flow a tiny bit, but the overall effect of the smoother bores and such makes them flow more. Second opinions, will a Mighty Demon 750 flow as least as much as the Avenger 770 I had? Cuz that seemed good enough for my purposes. Is the modest sounding "750 Mighty" actually, in real world application, going to be like a much bigger Holley? Cause if it's as "tight" as a 750 range carb, but can rev like a bigger carb, it seems like 750 might be the ticket(?)

I don't care about 20 extra HP at 6000rpm, I care that the engine will be crisp and clean if I stab it from 2000 to 4000rpm. Heck, stabbing it at 1500 and not having it bog dead would be fun....

I had a Mighty Demon 850 annular on my 489 with an XE294. (250/256@.050 .588/.593 110)

It worked well for me, easy to tune, and idled much better than the Holley I had with the plates drilled. I was very happy with it.

i like annular's better. i did 2 383 strokers the first one had a 230/236 at .050 comp cam with a 650 speed demon, ran great. second one i did a year later for the same car had a 244/250 solid cam and also changed to a victor jr from a rpm and went to a 750 annular mighty demon. the second one with bigger cam carb and intake had way more bottom end than the first one, figure it was alot to do with the annular, idles good very streetable. my 2 cents

Is that our final answer? What if I posed the question this way...."At elevated rpm, a 750 Mighty Demon flows like an NNN Holley 4150". What do we guess, from the seat of our pants, would that NNN Holley be? 800? 850?

Gibbons,

Any reason you are limiting yourself to only BG stuff?

IMO, with your combo I'd look into a Pro Systems prepped 950HP. Call Patrick, give him the stats on your combo and he will set you up with an awsome carb. Super crisp throttle response with great power throughout the power band. You wont be sorry. :yes:

http://www.prosystemsracing.com/index1.html

Gibbons,

Any reason you are limiting yourself to only BG stuff?

IMO, with your combo I'd look into a Pro Systems prepped 950HP. Call Patrick, give him the stats on your combo and he will set you up with an awsome carb. Super crisp throttle response with great power throughout the power band. You wont be sorry. :yes:

http://www.prosystemsracing.com/index1.html

:thumbsup: