Holley 950 Ultra HP Carb

General engine tech -- Drag Racing to Circle Track

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63qcar
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Re: Holley 950 Ultra HP Carb

Post by 63qcar »

Spike ..... to expand somewhat on what others have said about sizing the PV to cruise vacuum ..... good advice . My application may be a little different from yours , but I used to put my Cobra replica w/482 FE engine with a 4150 mechanical secondary carb on road courses . Idle vacuum is about 8 to 9 inches . Coming out of turns under part throttle throttle , I had a huge hole around 2700 rpm ( transition to mains ?? ) as I rolled into WOT and then it came on strong above that . It went way lean . Turns out the 6.5 PV wasn`t seeing enough vacuum to open it until I floored it . Solution was a 10.5 PV .... engine was still crisp and no more flat spot . Also , works on the street on winding back roads .
I`m also using that same PV rating on the street with no issues . Also still using primary and secondary PV and tried a 1:1 primary to secondary link , but that was too aggressive , so went to one where primary opens about 30% before the secondaries come in .
BTW , this is one of Mark W`s carbs , also have another one he reworked for me ...... listen to him , he won`t steer you wrong .
I think you asked about what size TSR to start with ..... my carb wanted .080 to 082 . Just a suggestion .
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Re: Holley 950 Ultra HP Carb

Post by rgalajda »

Tuner wrote: Mon Mar 13, 2023 12:30 pm
rgalajda wrote: Mon Mar 13, 2023 6:25 am Tuner , can you explain why no power valve on the secondary?
If the secondary will only be used for WOT such as in drag racing a PV isn't necessary and slows nozzle response to rapid secondary opening.

A secondary PV is useful in a vehicle that spends significant time at 70%+ engine speed and under 50% load at part throttle, such as in circle track and road racing or some boats.

For a drag race car that will 60' better than 1.60 or so, how would you put a "jet extension" on a secondary PV?
So no advantage on a street car?
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Re: Holley 950 Ultra HP Carb

Post by Tom68 »

rgalajda wrote: Tue Mar 14, 2023 3:51 am

So no advantage on a street car?
Depends what you're doing with it.

Street and Strip, no need for a secondary PV.

Street and circuit race, PV will help with a good AF throughout the throttled range, but not a necessity.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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Re: Holley 950 Ultra XP Carb

Post by USMC_Spike »

Anyone have the exploded view diagram of the Holley 950 Ultra XP Carb.

Nothing I've found show it. I've got a few parts I"m not sure of where they go, imagine that.
I've got a heavy spring that I don't know where it came from.
And a linkage part, and another part, that I'm not sure of.

Holley's site doesn't show an exploded view of the 4150 950 Ultra XP Carb.
At least that I can find.

--thx Spike
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Re: Holley 950 Ultra XP Carb

Post by HQM383 »

USMC_Spike wrote: Fri Mar 17, 2023 9:29 pm Anyone have the exploded view diagram of the Holley 950 Ultra XP Carb.

Nothing I've found show it. I've got a few parts I"m not sure of where they go, imagine that.
I've got a heavy spring that I don't know where it came from.
And a linkage part, and another part, that I'm not sure of.

Holley's site doesn't show an exploded view of the 4150 950 Ultra XP Carb.
At least that I can find.

--thx Spike
Post pics of parts?
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
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Re: Holley 950 Ultra HP Carb

Post by bobmc »

there is no "heavy spring" in that style carb, it must be from something else
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Re: Holley 950 Ultra HP Carb

Post by FC-Pilot »

Any exploded view of a standard double pumper should help. They are all cut from the same cloth.

Paul
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Re: Holley 950 Ultra HP Carb

Post by Ks Fats »

Doesn't the Ultra have the adjustable idle bleed set up under the carb stud? There is a relatively heavy spring in that arrangement.
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Back from spring break.

Yes, that is what I was thinking also, Ks Fats, but wasn't sure.
Everything else is kind of like putting the puzzle back together.

Interesting now that I've but the base plate back together, that
the primary throttle openings don't close all the way. There is a
slight opening about a sheet of paper thick on the half that is
by the t-slots. The t-slot is just barely visible with the throttle
in the closed position.

I've got to catch up here and will get back with any other information as I come across it.

--thx Spike
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Where does the spring go?

Here are the pics of it. It doesn't go in any of the places where
I've taken pics.
It's not a pump spring:
03.01 SpringWhere.jpg
Not on the center Carb bottom either as I'm sure
it would have left marks on the Anodize finish:
03.02 SpringCenter.jpg
nor here:
03.03 Spring Center.jpg
If the spring fit on the bottom, I would assume it would
leave a mark in the center of the throttle plate, but no mark:
03.04 NoSpringMarks.jpg
And it makes no sense to have it on the top here,
as it could too easily fall down the throats into
the engine. Here it is on top:
03.05 SpringTop.jpg
So my question is where did it come from? It came from the carb,
I can't recall where.

I'm all ears.

---thx Spike
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Re: Holley 950 Ultra XP Carb

Post by USMC_Spike »

Reminds me of an engine swap we did in the 90s where
we ended up with a handful of nuts and bolts.

--Go figure
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Spent hours and hours on the phone waiting for some type of technical support from Holley.

Couldn't keep waiting will try again tomorrow.
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Interesting, got a human at Holley,
I was told the spring goes in there with
idle air adjustment in the carbs center.
It holds the adjustment screw in place.

Strange that I didn't take that apart yet have the spring?

He said it was similar to the demon carbs.

Time to put that together and see how it idles now.

--thx Spike
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

UPDATE

Putting it together, final cleaning parts, etc.
Not full time, but getting there slowly but surely.

--thx Spike
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

UPDATE:

I pulled the center air screw (more like an open jet) and there is no spring in there.
The spring I show sticking out, a few posts prior to this, will not go inside the hole
to provide tension. Holley said it was like the DEMON carb, but no way.

My thinking it to see of there is a nylon washer that I would place the bottom end
when I put the carb together. But then I would need a washer on the top resting
against the brass otherwise small brass shavings would get into the engine.

I"ll put the piece back in and lube it with some red 'n tacky grease. Hopefully,
that should keep it from moving over time.

When cleaning for final assembly I found that the secondary squirter jet was stuck.
The small pointy piece wasn't moving at all. That secondary squirter looked brand
new, like there was ever fuel through it a all.

The squirters are both #31.

Getting closer now.

--thx Spike
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