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Author
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Topic: 351C - Why a 950HP??
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MrWesson22
Gearhead Posts: 1209
From: Dacula, GA
Registered: Sep 2000
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posted 03-16-2003 05:01 PM
   
I'm going to be buying a Holley HP carb for my cleveland very soon, but I'm still debating on the size. The application will be about 70% strip/30% street. It's a 4.11 gear (28" tire), and shift point is 6500-6700. I'm just thinking the 950HP will load up too much when it is on the street. I mean, if it were race only, I'd be running a tunnel ram with twin DPs. Wouldn't a 750 or 830 be enough? O wise and all-knowing Cleveland gurus, please help me out here.  Thanks.
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Neal 69 Gulfstream Aqua Grande
351C/4sp
https://mustangsandmore.com/ubb/MrWesson22.html
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-16-2003 05:05 PM
With good ignition, I have never had a motor "load up". Not even when I ran an 850 dp on the street.My car really responded well to the 950HP. However, yours may be better suited to a 750HP. As for race only, tunnelrams are way over rated. The only way I would ever use one on my cleveland is if it had a hat on top and was alchy injected.
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-16-2003 05:10 PM
And as a side note, a 950 does not flow 950 cfm. I have been told it is closer to 875 or 900 than 950.
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steve'66
Gearhead Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 03-16-2003 05:22 PM
What does an 830 hp flow?SteveW
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Mpcoluv
Gearhead Posts: 945
From: Charlotte NC usa
Registered: Apr 2001
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posted 03-16-2003 05:40 PM
quote:
Originally posted by steve'66:
What does an 830 hp flow?SteveW
An 830 is an annular discharge carb which would be a good compromise between the 750 and the 950 IMHO.
The annular boosters sprays the fuel in a finer mist that "normal" boosters.
A lot of people like the annular boosters when running a single plane intake on a street/strip car....
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methylated
Journeyman Posts: 43
From: wytheville,va usa
Registered: Mar 2003
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posted 03-16-2003 06:12 PM
the 950 hp is probably the best 4150 holley makes ,they have done what carb specialty shops have been doing for years ,bolting an 850 baseplate to a 750 body . That way you get more airflow and stronger jet pull all at the same time . by the way some carb shops do this mod and that is basically all they do and charge a premium for their services. the prob with a straight 850 is weak jet pull you can sometimes jet up/down and see little difference, and of course a 750 is sometimes to small ,anyway the 950 will probably work anytime a 750 would'nt be too much. I havent tried it ...yet, but I bet it would .
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-16-2003 06:42 PM
When I ran an 850, I jetted it up so much trying to get color on the plugs it slowed down over a tenth, and still wouldn't color the plugs. My 950 idled good, started great and ran fantastic. At least it ran good enough that I won 6 races that year and the points championship. As a side note, the 950HP was 3 tenths faster in the 1/8 than my 750 annular discharge DP was.
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MrWesson22
Gearhead Posts: 1209
From: Dacula, GA
Registered: Sep 2000
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posted 03-16-2003 06:44 PM
So should I run a 950 or a 750? 950 just sounds like way too much carb for a street/strip 351. I dunno.
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Neal 69 Gulfstream Aqua Grande
351C/4sp
https://mustangsandmore.com/ubb/MrWesson22.html
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-16-2003 06:50 PM
If your combo was mine, and I needed to buy a carb for both the street and the track, I owuld buy a 750 HP, with mechanical secondaries. If it was race only, I would buy the 950. But since your motor is not as radical as a pure race motor, I think the 750 would be the better choice.
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70coupe
Gearhead Posts: 357
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 03-16-2003 07:02 PM
I've tried both a 750HP and a 950HP on my high 11 second mustang. There is very little difference in performance between the two. I ran about .02 faster with the 750HP but that is with my set up. If you plan on keeping your motor in my horsepower range (425HP) then I would stick with the 750HP but if you plan on moving up to a 10 second motor buy the 950HP.
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351c 4v clsd heads
60'1.619
1/8 [email protected]
1/4 [email protected]
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MrWesson22
Gearhead Posts: 1209
From: Dacula, GA
Registered: Sep 2000
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posted 03-16-2003 07:12 PM
My goal is to eventually run ~11.70s on motor with a streetable suspension. The only way this cleveland will ever see 10s is on the bottle. I'm getting the 750. Thanks a bunch for the advice!
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Neal 69 Gulfstream Aqua Grande
351C/4sp
https://mustangsandmore.com/ubb/MrWesson22.html
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steve'66
Gearhead Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 03-16-2003 07:12 PM
So what is a 830hp? Is it inbetween the two or some other animal?I got a new 830hp for the 440 project and a 850dp'r on the 408w. Which carb should be on which motor? Which one flows more? SteveW
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-16-2003 09:01 PM
If the 830 is an annular discharge, it wont flow near as much as an 850. Those big boosters might help low speed atomization which in turn helps throttle response, but they are a huge hinderance when it comes to flowing vast quantities of air. The 830 would be a good street carb on the 440, but I think the 850 would be a better racecarb.
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clevelandstyle
Gearhead Posts: 638
From: Connersville, IN
Registered: Jul 2001
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posted 03-16-2003 10:13 PM
My Holley book shows these dimensions for venturi size and throttle bore size.4779 750cfm
pri venturi= 1 3/8"
pri throttle= 1 11/16"
sec venturi= 1 3/8"
sec throttle= 1 11/16" 4788 830cfm
pri venturi= 1 9/16"
pri throttle= 1 11/16"
sec venturi= 1 9/16"
sec throttle= 1 11/16" 4781 850cfm
pri venturi= 1 9/16"
pri throttle= 1 3/4"
sec venturi= 1 9/16"
sec throttle= 1 3/4"
I appears that a 830 has an 850 body with a 750 base. I was under the impression that some 830s have annular boosters. I don't have a listing for any such thing, so I dont know the bore sizes. My book is old. 
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Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 351C 4V
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7DMACH1
Gearhead Posts: 1430
From: PHILA. PA.
Registered: Feb 2001
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posted 03-16-2003 10:30 PM
My 408c dynoed the most hp with a 800dp. That's what I'm running. Every combenation is different. I would think a 950 is too big. RAy------------------
RAY, THE WISE A@@ PHILLY GUY!!Click HERE for My Cruise Night!! http://www.mustangmods.com/publish/7DMACH1/CRUISE%20NITE%20DOMESTICS%20ONLY%20SMALLEST.JPG
CLICK FOR MY PHOTO ALBUM
http://community.webshots.com/user/7dmach1 http://mustangsandmore.50megs.com/MembersPics/7DMach1.htmL
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Mpcoluv
Gearhead Posts: 945
From: Charlotte NC usa
Registered: Apr 2001
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posted 03-17-2003 09:05 AM
quote:
Originally posted by clevelandstyle:
I was under the impression that some 830s have annular boosters. I don't have a listing for any such thing, so I dont know the bore sizes. My book is old.
Most of the 830s I have seen are annular discharge. From Holleys website the HP carb Part #: 0-80511-1 is pictured with annular boosters.
http://holley.com/HiOctn/ProdLine/Products/FMS/FMSC/0-80511-1.html
I only mentioned annular boosters because some street driving was mentioned.
The Big boosters DO hurt airflow at the expense of better (in theory) low end.
The first 830 annular (still in production as 0-9381 with choke tower but no choke)was designed for the 350 SBC NASCAR short track spplications. BTW NASCAR mandated a 1 11/16" throttle bore.
http://holley.com/HiOctn/ProdLine/Products/FMS/FMSC/0-9381.html
There is also a 1000HP with annular boosters.
http://holley.com/HiOctn/ProdLine/Products/FMS/FMSC/0-80514-1.html
Has anyone tried this one? [This message has been edited by Mpcoluv (edited 03-17-2003).]
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'69Stang
Gearhead Posts: 180
From: Detroit, MI USA
Registered: Jan 2002
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posted 03-17-2003 10:21 AM
Wow, I'm confused. I was strongly encouraged to get a 950 HP and now I/m wondering if it is too big. it definitely causes problems at idle, soots up the plugs, but seems fine @ WOT. What is the right carb recommendation for a 450 - 500 horsepower 351C that is 70% street?------------------
'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb intake, ported 4-v quench heads, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear
------------------------- 12.51 1/4 mile @ 115.89
60 foot time 2.008 (ouch)
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Mpcoluv
Gearhead Posts: 945
From: Charlotte NC usa
Registered: Apr 2001
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posted 03-17-2003 10:40 AM
quote:
Originally posted by '69Stang:
Wow, I'm confused. I was strongly encouraged to get a 950 HP and now I/m wondering if it is too big. it definitely causes problems at idle, soots up the plugs, but seems fine @ WOT. What is the right carb recommendation for a 450 - 500 horsepower 351C that is 70% street?
What tuning steps have you tried?
Do you have a 4 hole spacer? Can you see fuel drip from the boosters at idle?
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kid vishus
Gearhead Posts: 4538
From: middle of NC
Registered: Oct 2000
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posted 03-17-2003 10:53 AM
Something must not be tuned right. Have you changed powevalves? Are the floats too high?I ran my 950HP on a 9-1 compression, hydro cammed cleveland that was not making anywhere near 450 hp, and it worked great. It idled good and never once fouled or sooted a plug, started great and still was 3 tenths faster than my 750 annular carb in the 1/8, even on that mild motor.
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70coupe
Gearhead Posts: 357
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 03-17-2003 10:59 AM
The 950 should be fine for street or strip on any cleveland. I just feel for the street a 750 would be best. However, the 950 should run and idle just fine. Something must be out of adjustment somewhere. Are they stock power valves in the carb? What kind of vacuum readings do you get from this motor?
When I ran the 950 the throttle response was crisp and it worked very well. I just didnt need that much carb as my tests proved.
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351c 4v clsd heads
60'1.619
1/8 [email protected]
1/4 [email protected]
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MrXerox
Gearhead Posts: 326
From: Oklahoma City, Oklahoma
Registered: Nov 2000
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posted 03-17-2003 02:16 PM
Again, I have tried the 750dp, 850dp and 950hp on my 11:1 244 @ .050 .623/.623 solid roller (same cam as Ray has in his 408c) and my primarily street driven Mach runs MUCH better with the 950 than it did with the other two. Trust me, it is not too big...
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clevelandstyle
Gearhead Posts: 638
From: Connersville, IN
Registered: Jul 2001
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posted 03-17-2003 05:10 PM
Again, for those how think the 950 is too big. It does NOT flow 950cfm. It is basically a souped up 750. It has the 1 3/8" venturi of the 750, but with 1 3/4" throttle blades. In reality, it should be more responsive than a 750 because of stronger jet pull.------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 351C 4V
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'69Stang
Gearhead Posts: 180
From: Detroit, MI USA
Registered: Jan 2002
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posted 03-18-2003 12:27 PM
This particular 950HP I'm using is actually a modified version done by Quik-Fuel and seems more suited for a big block or more radical engine. The engine pulls great vacuum, ~14"-15", but the engine loads up to the point that it wants to stall at idle, particularly in sub 60 degree weather. Well I come to find out that the idle fuel restrictors are smaller than normal so they let out a lot of fuel at idle. I compensated by putting in bigger air bleeds in order to compensate for the mixture and it helped out somewhat, and played with the butterflys and mixture screws. Essentially , the spark plug strap and porcelain look fine, it is just that the threads and cup are sooted and black, which tells me that the idle is rich. I played around with the carb to where it is now acceptable. Anyway I am getting a new 950 HP from Wilson carb's that is tailored to my engine (a buddy wants the Quik Fuel carb for his 455) which should clear up this idle situation. The carb in all other respects seems to be just right for Clevelands, and I have to say that the box stock Holley 950 HP would probably be perfect for most hot street apllications and above.
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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb intake, ported 4-v quench heads, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear
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12.51 1/4 mile @ 115.89
60 foot time 2.008 (ouch) [This message has been edited by '69Stang (edited 03-18-2003).]
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