Posted By: mopar dave
venturi size of 850 and 950 holley? - 11/11/12 03:58 AM
anyone know the venturi sizes for 850 and 950? just curious here as i have what bigs performance calls a 950 stage 5+,but the main body is stamped 850 and has 1.400 venturi's.
Posted By: B1MAXX
Re: venturi size of 850 and 950 holley? - 11/11/12 04:01 PM
I'm just going off memory but I think that the Holley 950's are 1.38 and their 850's are 1.56.
I never "got" the 950 rating based on that.
Posted By: Von
Re: venturi size of 850 and 950 holley? - 11/11/12 04:29 PM
[quoteyou're correct on size. the 950cfm rating is bogus.
Or is the 850cfm rating bogus? Or is the 1000 cfm rating bogus on the HP carbs which have the same size venturis and throttle plates as the 4781 850s?? 
Or should all CFM ratings be taken with a grain of salt?
The 950 PF main body venturis are smaller than the Holley 950 main body.
Posted By: BIGS
Re: venturi size of 850 and 950 holley? - 11/11/12 04:35 PM
Dave....these guys are correct.....
Old style 850 Holley are 1.560 Venturi X 1.750 Butterfly
Holley List #80496 950 1.375 Venturi X 1.750 Butterfly
On our 950 Stage 5 we keep the venturi at the stock 1.375
and on our Stage 5 950 Plus carb we open the venturi up to 1.400 by opening up the customers HP body or we also will use the Proform "850" body which already has the venturi at 1.400..
Hope this helps...Jesse
Posted By: Sb Valiant
Re: venturi size of 850 and 950 holley? - 11/11/12 06:01 PM
Most people that run 850 say they are going to step up to a 950 cfm carb the following year well what some people don't know is it's actually a smaller carb and has more cfm. The point is You can make a big carburetor small but you can't make a small carburetor big. Naturaly the 950 just works better.
Posted By: shoebox
Re: venturi size of 850 and 950 holley? - 11/11/12 06:36 PM
The 950/1000 HP hollers are a marketing ploy from Holley. Their 750
Carbs tested at a higher pressure that's it. Their a lie
Posted By: emarine01
Re: venturi size of 850 and 950 holley? - 11/11/12 09:44 PM
The same for Barry Grant stuff, the CFM ratings are different for the same size carbs
Posted By: mopar dave
Re: venturi size of 850 and 950 holley? - 11/11/12 10:55 PM
ok,so with 1.400 venturi and a 1 3/4 blade my carb would be closer to what size carb? 800?
Posted By: BSB67
Re: venturi size of 850 and 950 holley? - 11/11/12 11:04 PM
It would be nice to see actual flow data using a standardized method conducted at several different differential pressures, say .5 to 2.0 "hg.
Venturi size is not necessarly the defining element for air flow. There are several aspects that will effect the flow. Slight changes in shape and contours can have a large impact on air flow.
Another item of note is that on my 4781, the boosters are different than on my 950. They are thicker and look like they would be more restrictive to flow.
With all that, it is hard to believe that the 950 (1.375" venturi) flows more air than the 4781. However, on my car, the 950 is 1 mph faster, and .2 sec quicker.
Posted By: mopar dave
Re: venturi size of 850 and 950 holley? - 11/11/12 11:20 PM
Just tryin to figure out what my carb is simular to in holley size wise so i can look at stock jetting. Went to the track with 76/84 jetting and put 82/90 jets with a new 4.5pv and it liked this time. Never liked it before.
Posted By: BSB67
Re: venturi size of 850 and 950 holley? - 11/11/12 11:26 PM
My low et in cool air was 77/84 in my 950.
Posted By: mopar dave
Re: venturi size of 850 and 950 holley? - 11/11/12 11:42 PM
And thats on a 500ci? I thought their was something not quit right with my jetting. Almost like the power valve is not opening.
Posted By: deaks
Re: venturi size of 850 and 950 holley? - 11/12/12 12:36 AM
I thought the smaller venturi on the 950, made for a better shift recovery.
Andy, what exactly do you mean by a larger engine.
500 and up ?
Mick