Whats the difference ? 4150 question !

-
MOPARMAGA

MOPARMAGA

" The other hard member"
FABO Gold Member
Joined
Aug 20, 2019
Messages
10,479
Reaction score
11,204
Location
Yakima Wa
Hey a-buddies I have a question about holley 4150s.
I'll start with the statement, on the 830-850-1000 cfm classic hp holley the venturies are identical at 1.561 (or somewhere around there) however the 830 uses a similar sized throttle plate & 850-1000 use a 1.750 throttle plate. (950 too but not in this equation)
The question is, what's the difference between the 850 & 1000 if their physically the same & with a bit of grinder work can I get my 830 to have a 1.75 plate & copy the jets, squiters, air bleeds & boosters to achieve a 1000 cfm.
I'm sure many of you smart folks have tried, we're you successful ?
 
Venturi diameter AND throttle blade size are the basis for CFM ratings.

CFM ratings are a poor way to chose a carb size. You can buy a...say a BLP BX4 carb with a 1.350 venturi and 1.687 throttle bore and it’s rated at 650 CFM but in actual practice it will flow the better side of 750 CFM. Take that same 1.350 venturi and use a 1.750 baseplate and the CFM will go up another 50-75 CFM.

If you are using a main body that has/had a choke horn, I’d shelve it and buy a ProForm main body for it and start there.

If you can find one FST has a carb that is under 500 bucks that has all the bells and whistles and it comes in 1.350 and 1.410 venturi. The former is rated at 650 CFM and the latter is rated at 750 CFM.

Finding one may be near impossible.
 
The 750 4150 was rated 780 as a 4160...downleg boosters and another metering block?
 
yellow rose said:
Venturi diameter AND throttle blade size are the basis for CFM ratings.

CFM ratings are a poor way to chose a carb size. You can buy a...say a BLP BX4 carb with a 1.350 venturi and 1.687 throttle bore and it’s rated at 650 CFM but in actual practice it will flow the better side of 750 CFM. Take that same 1.350 venturi and use a 1.750 baseplate and the CFM will go up another 50-75 CFM.

If you are using a main body that has/had a choke horn, I’d shelve it and buy a ProForm main body for it and start there.

If you can find one FST has a carb that is under 500 bucks that has all the bells and whistles and it comes in 1.350 and 1.410 venturi. The former is rated at 650 CFM and the latter is rated at 750 CFM.

Finding one may be near impossible.
Click to expand...
Thanks Tim, starting with a classic hp so no choke the carb is 830 cfm 80509 part number.
I'm really just trying to figure out if I can make the carb I have feed 471 cubes @ 6800-7000 rpm by just adding a 1.750 throttle & upping the squirters to match the larger holleys
 
MOPARMAGA said:
Thanks Tim, starting with a classic hp so no choke the carb is 830 cfm 80509 part number.
I'm really just trying to figure out if I can make the carb I have feed 471 cubes @ 6800-7000 rpm by just adding a 1.750 throttle & upping the squirters to match the larger holleys
Click to expand...

I'd buy a bigger carb and sell the 830 before I started grinding on it. The booster style will also change cfm's.
 
justinp61 said:
I'd buy a bigger carb and sell the 830 before I started grinding on it. The booster style will also change cfm's.[/QUOTE

I agree with this. There are so many better choices out there, but they are not always cheap. But the pay once, cry once fits here. I’ll find some links to what I think I would use and then post them in this thread.
Click to expand...
 
My Braswell 4825 is a 1.48 venturi 1.79 throttle blade..... swapped intakes so I’m running a 4500 now. Went some 9.4s with the Braswell.
 
A body said:
My Braswell 4825 is a 1.48 venturi 1.79 throttle blade..... swapped intakes so I’m running a 4500 now. Went some 9.4s with the Braswell.
Click to expand...

So the 4825 is a 4150. That’s what I thought. At this point I think a Dominator with a tapered spacer isn’t as bad as I thought it was.
 
yellow rose said:
So the 4825 is a 4150. That’s what I thought. At this point I think a Dominator with a tapered spacer isn’t as bad as I thought it was.
Click to expand...
Oh okay, thanks for all the options to consider
 
MOPARMAGA said:
Thanks Tim, starting with a classic hp so no choke the carb is 830 cfm 80509 part number.
I'm really just trying to figure out if I can make the carb I have feed 471 cubes @ 6800-7000 rpm by just adding a 1.750 throttle & upping the squirters to match the larger holleys
Click to expand...
I run a 1000 Pro Systems 4150 style on my 470 stroker. I went from a 750 AED and picked up 2 1/2 tenths. I’m going to a Super Victor and a 1250 dominator. Kim
 
oldkimmer said:
I run a 1000 Pro Systems 4150 style on my 470 stroker. I went from a 750 AED and picked up 2 1/2 tenths. I’m going to a Super Victor and a 1250 dominator. Kim
Click to expand...
Thanks Kim, that's a nice carb
 
MOPARMAGA said:
Thanks Kim, that's a nice carb
Click to expand...

My original 830 was essentially what they call a 950 today. 750 main body with an 850 base plate. It was a good carb. Be careful with the 1000cfm 4150 carbs they can be hard to tune and booster signal recovery can be an issue at the shift points. I have two annulars and one down leg 1050. They are awesome on a 499-511 but an 850 or even 750 was better on a stock stroke 440. Just my experience on a few different cars ymmv.
 
So, anyone got any thoughts on what a garden variety 4779 / 750 might flow with and without the choke tower?,...thanks
 
raymond said:
So, anyone got any thoughts on what a garden variety 4779 / 750 might flow with and without the choke tower?,...thanks
Click to expand...


IIRC, it doesn’t flow much more if any at all with the choke tower off.

What it does affect is driveablity. A nebulous term for sure, but it is a “a thing”. If you look at a carb with a choke horn on it and the air filter base and filter sitting on it, you can see that the choke tower blocks off a big section of the filter. So the air coming in through the filter has to hit the choke tower, go vertical, then make a 180 degree bend to get into the carb.

Air does not like to bend more than 7-8 degrees before it starts getting real turbulent (I’m sure there’s a Reynolds number for it but I don’t know what that is), remembering that the flow won’t be laminar.

I’ve said before I don’t get too excited about CFM ratings. They are a buckshot accurate guesstimate of what a carb CAN flow at 20.4 inches of water.

You can put a 4779 on a 273 and it will flow “X” amount of air. Take that same carb and mount it to a 540 and it will flow “Y” because the bigger displacement will generate a greater pressure drop.

Of course, if we are discussing pumping losses, the bigger carb always wins that, up to the point you lose booster signal and the fuel curve gets shot to hell. Of course, there are boosters that will generate a much greater signal at lower air speeds through the booster...but what about the fuel curve at higher RPM?????

So there is that.
 
The question is, what's the difference between the 850 & 1000 if their physically the same
Click to expand...

What you’re asking is...... where is the “extra 150 cfm” coming from?
The answer to that is....... the marketing dept.

From several years ago.......
The Mighty Demon 850 vs the Race Demon 1000.
Same sized everything........ but the Race Demon has more circuit tunability.........and costs a lot more...... so it’s a “1000” instead of an 850.
And if you got the same sized Race Demon RS......it was a “1025”........ even though it didn’t actually flow anymore.

It’s just more marketing genius.

Personally....... I don’t really care for the “830” configuration(1.56v x 1.687 bore).
I believe the “street HP 850” might also use that venturi/bore combo.
 
Last edited:
PRH said:
What you’re asking is...... where is the “extra 150 cfm” coming from?
The answer to that is....... the marketing dept.

From several years ago.......
The Mighty Demon 850 vs the Race Demon 1000.
Same sized everything........ but the Race Demon has more circuit tunability.........and costs a lot more...... so it’s a “1000” instead of an 850.
And if you got the same sized Race Demon RS......it was a “1025”........ even though it didn’t actually flow anymore.

It’s just more marketing genius.

Personally....... I don’t really care for the “830” configuration(1.56v x 1.687 bore).
I believe the “street HP 850” might also use that venturi/bore combo.
Click to expand...
Okay thanks, a couple people have told me its
PRH said:
What you’re asking is...... where is the “extra 150 cfm” coming from?
The answer to that is....... the marketing dept.

From several years ago.......
The Mighty Demon 850 vs the Race Demon 1000.
Same sized everything........ but the Race Demon has more circuit tunability.........and costs a lot more...... so it’s a “1000” instead of an 850.
And if you got the same sized Race Demon RS......it was a “1025”........ even though it didn’t actually flow anymore.

It’s just more marketing genius.

Personally....... I don’t really care for the “830” configuration(1.56v x 1.687 bore).
I believe the “street HP 850” might also use that venturi/bore combo.
Click to expand...
What do I need to figure out the right carb for my application? I've done the calculators & the 470×7000×.95÷3456= equation. Everything is telling me 1000-1050. Is this something I can only figure out on a dyno ? I guess I need more learning
 
What do I need to figure out the right carb for my application?
Click to expand...

Imo, if you don’t already know what you want.......you’re not likely going to find a real answer looking at some formula or on line calculator.

Call some reputable carb builders and get their recommendations.
If one of them gives you the warm fuzzy feeling...... have them sell you a carb.
 
PRH said:
Imo, if you don’t already know what you want.......you’re not likely going to find a real answer looking at some formula or on line calculator.

Call some reputable carb builders and get their recommendations.
If one of them gives you the warm fuzzy feeling...... have them sell you a carb.
Click to expand...
Agree. I would call Dominic, at Thumper Carbs. He is on moparts (sorry) and facebook. Mopar guy thru and thru, real carb guru. If you think you need more than an 850, i guarantee he will recommend a dominator. In my opinion, the claims of 1000cfm from a 4150 are just fantasy.
 
You must log in or register to reply here.
-

Back
Top