Flow tested a few carbs the other day, thought I'd share my findings. The Ultra HP carbs are the older design from around 2005 they are no longer sold.

Holley Ultra HP 750 part#80675
1.375 venturi / 1.687 base plate
819 cfm

Holley Ultra HP 950 part#80676
1.375 venturi / 1.75 base plate
825 cfm

Holley 850 "old style main body" part# 9380
Choke horn milled off, slabbed throttle shafts, annular boosters
1.58 venturi / 1.75 base plate
945 cfm

I'll be replacing the 1.375 main body of the 950 with a 1.45 main body and retesting in the coming weeks.

This test backed my suspicions about the true flow of the 950, as it was only able to make about 5 more HP than the 750 on an upper 500 HP 360 motor. 950 my ass lol, I know Holley took a lot of [censored] over that carb and the new XP950 has a 1.6 venturi because of it.

Kinda explains why I like me my proform 850 so much. It may be flowing more than I think it is

Carb companies would be better off just listing the venturi diameter and base plate diameter than giving us BS CFM ratings.

Been known for a long time. Most small block guys jump from a 750 to a 950.
The 850 is more commonly used on big blocks

Be aware that that new 950 with the 1.60 venturi is a poor choice. The entrance shape causes turbulence. I've had 3 on my flow bench, put every booster available in it. Flow and booster signal are down because of it, and I can get a 1.45 venturi Quick fuel to flow the same and have a much better booster signal. And you can hear the turbulence on the bench. Quick Fuel/Proform bodies are a much better choice, the entrance to the venturi is shaped better, as well as the new billet bodies from BLP and APD.

I've heard that about the 950 XP. That's why I'm working with the 1.45 QFT main body. Should be a good match to my engine.

^^^ Nice

wonder where my 1.48 venturi 1.79 would fall into that...

Is that a Braswell ?

hmmmmmmmmmm

wonder where my 950 3 barrel would fall in that mix ?????

back before the holley craze started in the mid-late '60's venturi and throttle bore sizes were the ratings. cfm ratings are bogus marketing tools.

If would be interesting to see what my 1.59" venturi BLP main bady and a 1.75" base plate would flow.

What, again?

FWIW, stuff I posted about 5 years ago:

Carb ----------------------------------------------------------Dry Flow -- Calc'd Wet

Holley 3310-2 "750" with choke ------------------------------ 796.6 ----- 732.9

Quick Fuel "950" 1.45 v body on Demon RS baseplate ----- 963.0 ----- 886.0

BG (Gold Claw / Demon RS) 1.425 venturi sleeve ---------- 958.1 ----- 881.5

BG (Gold Claw / Demon RS) 1.500 venturi sleeve --------- 1001.3 ----- 921.2

BG (Gold Claw / Demon RS) 1.562 venturi sleeve --------- 1012.0 ----- 931.0


Original thread LINK

BradH... Thread-Killer Extraordinaire.

Me too Brad, thanks for your info

And the question, relevant but never asked:
"Are all of those tests done on the specific engine which develops that intake vacuum with that carburetor (no more, no less), or on the same fixture?

Please: be rude, I'm used to it.

It's a reasonable question with an obvious answer.

It's also beyond my R&D budget to test them all in the manner you describe, interesting as the data might be.

I apologize - not faulting your valuable work, thank you.
Just pointing out that regardless of the rated vs. tested CFM a small engine won't pull enough vacuum to develop the rated CFM, and a big motor will run higher than the test vacuum (and more CFM), and perhaps enough to keep the low number PV closed...