[dell72]

I'm looking for suggestions on a 4150 Carb. Engine is a pump gas 540,AFR 305's, Straub hydraulic roller. I have a 950 HP, I could have modified if needed. Otherwise I'm looking at buying something new.

 

[jackie schmidt]

I run a HP 950 Ultra. 100 percent street car.

http://www.holley.com/0-80805BK.asp

That is what made the most power on my 540, 668 at 5800. I tried a Edlebrock 800 and a Quick Fuel 850 as well. Our engines, I think, are real similar, except I have a tad under 10 to 1 compression and 234-244 at .050 on the cam at .675 lift under AFR 290's.

I have been running it on the street for the better part of the year, and aside from not having a choke, (I live in Houston), it is a phenominol street carb.

Aside from being all aluminum, I am not sure there is a lot of difference between this and your HP.

 

[69-CHVL]

try a 1000hp.

 

[Indiansprings]

950 HP should do well. You could try the 1000 HP, I'm not sure it would be a big difference.
Do you think your needing more carb, or so you feel you need to tinker with something? Sometimes I feel I need to try a different part to get some more power. You can end up spending thousands messing around.
Sometimes the best thing we can do is really tune the car. Usually a lot of hidden power in those timing curves and jets.

 

[dell72]

This is a new build. Not in the car yet. Just trying to figure out if I can use what I have or not. I've seen similar builds using a 1000 cfm. I'm not sure what I would be giving up using the 950

 

[crazydavey]

Eric IIRC the 950hp actually flows around 830 or so. I don't have experience with the Ultra line that Jackie mentioned so I don't know if they are any different. I run a ProSystems 4150 1000 that flows 986 and the car loves it. It is very crisp and responsive and starts with the flip of the switch. It mostly depends on what you're going to be doing with the motor. If you are looking for all out performance then a custom build like the PS might be worth it for you. If it's mostly a street application you probably won't feel a heck of a lot of difference...

 

[BlackNova]

I have a prosystems hp1000 the nitrous version on my 540. flowed 992 cfm

 

[jackie schmidt]

I almost did not buy the Holley HP 950 Ultra because some supposed internet experts said it only flowed about 830. Well, it made over 30 more HP than the "true" 850, so it must be doing something right.

I talked to Holleys tech dept, and they assured me that the latest 950's did flow that.

But then, that is what I would expect them to say.

 

[dell72]

I have heard the old original 950 flowed about 830, but that the latest ultra hp actually flowed 950. But it is the internet........

 

[72BBMonte]

I have heard the old original 950 flowed about 830, but that the latest ultra hp actually flowed 950. But it is the internet........

When the Monte was setup to drive on the street a 950 hp that actually flowed 830 or whatever was quicker then a dominater on it. Two different dominaters tried. That was with a 750 horsepower 540ci Rat. The switch to the 950 HP was when it really started pulling the front tires.

A new HP 1000 probably would show better numbers on dyno but what you already have would probably run pretty good for no more investment.
This is what I observed.

 

[mc71454]

I've run a 4781C 850 DP with the choke tower still on to 10.40's at 129 and a Holley 1000HP to 10.30's., not the Ultra HP just the base model.

I also had a Prosystems 1000 HP that was no different (after bandaiding the stumble it had with a overly rich idle mixture) than the box stock Holley after a jet change and accelerator pump tuning I did to the Holley.

If you are street driving, the 950 or 1000 HP are great carbs and you will be fine with either one.

I have never heard of any Holley 950 or 1000 flowing more than 850 CFM. Are the claims of over 900 by using forced induction or unreasonable settings on a flow bench. Do they have larger than 1 3/4" openings in the base plate? an 850 DP has 1 3/4" bores in the baseplate a 950 is a 750 body on an 850 baseplate?

To really answer your question, Use your 950 Street HP you won't be sorry

 

[jmarkaudio]

I've had a fair amount of carbs across my flow bench. Here is what I saw.

Holley 4781 850 1.56 venturi .......... 960 CFM
HP 950 - Zinc 1.375 venturi .... 854 CFM
Ultra 950 Aluminum 1.600 venturi ...... 960 CFM
Ultra 850 Aluminum 1.56 venturi ...... 1019 CFM
Quick Fuel 950 1.45 venturi ......... 960 CFM
Quick Fuel 1000 1.50 venturi ......... 976 CFM
Quick Fuel 1050 1.56 venturi ......... 1019 CFM
Demon RS 975 1.50 venturi ......... 1006 CFM
I would expect the zinc body HP 1000 to flow similar to the Quick Fuel 1050 or the Ultra 850.

Notice that that the Holley Ultra 850 flows more than the Ultra 950 despite the larger venturi. I flowed two different 950's with the same results, and back to back with the 850. The Ultra 850 is a better choice. Also note that the Quick Fuel 950 flows the same as the Ultra 950 with a smaller venturi, it also has a much stronger booster signal than the Ultra 950 and also is a better choice. As far as the Quick Fuel 850, it has a 1.400 venturi and while I have not had it on a flow bench it likely flows between 860 and 900 CFM, less than the Ultra 950, so as long as the engine still distributed fuel well the Ultra 950 would make more power. However of all the carbs that flowed the same or more than the Ultra 950 ALL of them had a better booster signal than the Ultra 950, so it would be at the bottom of my list.

As far as what to use for the OP, if it is a street only car the HP 950 you have is a fine choice as the smaller venturi provide a very good booster signal, throttle response will be good as a result. If you run at the track and want more out of it the Quick Fuel 1000 or 1050 would be my choice. If you want to stick with Holley either the HP 1000 or Ultra 850.

 

[Indiansprings]

My HP 1000 did great on the dyno, we will see how it runs on the street and track by the end of the year, I hope.

 

[dell72]

Lots of good info, I've heard good responces from people using the quickfuel 950 & 1050 units. I don't know of anyone using a prosystems.

 

[jackie schmidt]

I've had a fair amount of carbs across my flow bench. Here is what I saw.

Holley 4781 850 1.56 venturi .......... 960 CFM
HP 950 - Zinc 1.375 venturi .... 854 CFM
Ultra 950 Aluminum 1.600 venturi ...... 960 CFM
Ultra 850 Aluminum 1.56 venturi ...... 1019 CFM
Quick Fuel 950 1.45 venturi ......... 960 CFM
Quick Fuel 1000 1.50 venturi ......... 976 CFM
Quick Fuel 1050 1.56 venturi ......... 1019 CFM
Demon RS 975 1.50 venturi ......... 1006 CFM
I would expect the zinc body HP 1000 to flow similar to the Quick Fuel 1050 or the Ultra 850.

Notice that that the Holley Ultra 850 flows more than the Ultra 950 despite the larger venturi. I flowed two different 950's with the same results, and back to back with the 850. The Ultra 850 is a better choice. Also note that the Quick Fuel 950 flows the same as the Ultra 950 with a smaller venturi, it also has a much stronger booster signal than the Ultra 950 and also is a better choice. As far as the Quick Fuel 850, it has a 1.400 venturi and while I have not had it on a flow bench it likely flows between 860 and 900 CFM, less than the Ultra 950, so as long as the engine still distributed fuel well the Ultra 950 would make more power. However of all the carbs that flowed the same or more than the Ultra 950 ALL of them had a better booster signal than the Ultra 950, so it would be at the bottom of my list.

As far as what to use for the OP, if it is a street only car the HP 950 you have is a fine choice as the smaller venturi provide a very good booster signal, throttle response will be good as a result. If you run at the track and want more out of it the Quick Fuel 1000 or 1050 would be my choice. If you want to stick with Holley either the HP 1000 or Ultra 850.

Interesting.
All I went by was the dyno numbers, and now the way the car drives. My HP 950 Ultra does have annular boosters, don't know if that means much.

I might get a 850 Ultra and see how it drives. I did not have access to one when we had my 540 on the dyno.

 

[71454Chevelle]

I've had a fair amount of carbs across my flow bench. Here is what I saw.

Holley 4781 850 1.56 venturi .......... 960 CFM
HP 950 - Zinc 1.375 venturi .... 854 CFM
Ultra 950 Aluminum 1.600 venturi ...... 960 CFM
Ultra 850 Aluminum 1.56 venturi ...... 1019 CFM
Quick Fuel 950 1.45 venturi ......... 960 CFM
Quick Fuel 1000 1.50 venturi ......... 976 CFM
Quick Fuel 1050 1.56 venturi ......... 1019 CFM
Demon RS 975 1.50 venturi ......... 1006 CFM
I would expect the zinc body HP 1000 to flow similar to the Quick Fuel 1050 or the Ultra 850.

Notice that that the Holley Ultra 850 flows more than the Ultra 950 despite the larger venturi. I flowed two different 950's with the same results, and back to back with the 850. The Ultra 850 is a better choice. Also note that the Quick Fuel 950 flows the same as the Ultra 950 with a smaller venturi, it also has a much stronger booster signal than the Ultra 950 and also is a better choice. As far as the Quick Fuel 850, it has a 1.400 venturi and while I have not had it on a flow bench it likely flows between 860 and 900 CFM, less than the Ultra 950, so as long as the engine still distributed fuel well the Ultra 950 would make more power. However of all the carbs that flowed the same or more than the Ultra 950 ALL of them had a better booster signal than the Ultra 950, so it would be at the bottom of my list.

As far as what to use for the OP, if it is a street only car the HP 950 you have is a fine choice as the smaller venturi provide a very good booster signal, throttle response will be good as a result. If you run at the track and want more out of it the Quick Fuel 1000 or 1050 would be my choice. If you want to stick with Holley either the HP 1000 or Ultra 850.

Thanks for the good info Mark. :yes:

As far as the HP1000, Patrick said my Pro Systems carb flows 980cfm, but not sure how acurate that is.

 

[DragRacer]

Mark,

Have you ever flowed a QF 950 with annular boosters?

Have one that is eating my lunch on the transition circuit in a 2200 lb car. Darn thing is so light it cruises on the trans. Circuit at any speed. 6 speed stick.

 

[jmarkaudio]

I would try going up on the idle air bleed .005, reset your mixture screws at operating temp. It will lean the transition and taper it off sooner to transition to the annulars. If it's on that 450" SBC I would get a QF 1050 body with downlegs to replace it.

 

[DragRacer]

Mark,

It's on a buddies car. 550 HP - SBF with way too big of heads. Will send you a PM as not to further get this thread off course.