Holley 950 Ultra HP Carb

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USMC_Spike
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Tuner wrote: Fri Mar 10, 2023 2:13 pm
Elroy wrote: Fri Mar 10, 2023 2:01 pm
Tuner wrote: Fri Mar 10, 2023 1:25 pm The 1.600" venturi has a spooky booster signal, but ? ?
Can you explain? I currently have one that doesn't run right.
LOL "doesn't run right" covers a lot of territory. Every carburetor I see "doesn't run right" in the sense that everything can be improved in some way, large or small. :D

I haven't had one of these in my hands, so I am repeating hearsay. What I am told by folks who have had them on a flow bench is, particularly with the down-leg booster, the signal doesn't increase at the same rate as required by the increase in air flow and the result is it doesn't require a lot of "Too Much Emulsion" to cause the A/F to trend lean as WOT RPM increases, so a jet big enough for high RPM is too big at low RPM. The stronger signal of an annular booster works better in this body with the 1.600 ID venturi.
I talked with Mark Whitener yesterday, we had a nice discussion. From Marks observations and flow measurements
there appear two issues with the Holley 950 Ultra XP.
1. The Venturis are too large with the inlet angle being greater than 30*
2. Number 1 causes the Venturi bottom air flow to churn causing reversion.
3. The down leg booster being 1.60", possibly too large has poor signal 1 & 2 above.

There are possible solutions to the above which Mark and I discussed.
One possibility might be some sort of insert.

Mark also designed a booster that can be installed in this
carb to give it better signal.

There is also a different carb main body that can be used with the Holley 950 Ultra XP
that should work better than the factory main body.

These will be investigated at a later date.

Yes, I assumed Mark got busy doing TV Sports Audio. That is why I didn't pester him with
phone calls. We have similar background in TV, Basic Electronics, and production, etc.

--thx Spike
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steve cowan
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Re: Holley 950 Ultra HP Carb

Post by steve cowan »

20211204_140251.jpg
20211204_140318.jpg
Here is a close up of the 950 Ultra xp mainbody.
I have asked before about the step venturi, there has been many opinions on this.
With that booster it may need larger than normal jet size to meter the fuel requirements
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

@Steve, not sure what you are asking.
I've posted pics of the carb in the thread.

The boosters have a step cut in them like the Ultra 950 HP.
The venturies have a cast step in them similar to the Ultra 950 HP.

Pic is on page 2, and here it is again:
01.05 HolleyXP CU Bottom.jpg
You can see the step on the casting from the carb bottoms pic.

--thx Spike
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Re: Holley 950 Ultra HP Carb

Post by steve cowan »

USMC_Spike wrote: Sat Mar 11, 2023 6:41 pm @Steve, not sure what you are asking.
I've posted pics of the carb in the thread.

The boosters have a step cut in them like the Ultra 950 HP.
The venturies have a cast step in them similar to the Ultra 950 HP.

Pic is on page 2, and here it is again:

01.05 HolleyXP CU Bottom.jpg

You can see the step on the casting from the carb bottoms pic.

--thx Spike
I wasn't really asking anything, just wanted to show a new mainbody I bought last year,I was originally going to buy a new 850 ultra XP and Inter change and test with the 950 mainbody.
I have since scrapped that idea.
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Re: Holley 950 Ultra HP Carb

Post by rgalajda »

To begin with David Vizard is not wrong about Power Valve selection.
From his book “ Be sure to use a power valve that switches at a lower vacuum than the idle or cruise vacuum” ( Higher of the two )

You have two things going against you . That is not a street cam and that carb with a 1.6 venturi is to large for the street without annular boosters.
If that was my car, the cam would be changed . Probably 231@.050 maximum for the street.

The carb that 1980RS mentioned #80496 950 CFM Classic HP is an overrated 850 cfm carb.
Regardless , it is a good carb for the street/strip because of the much smaller venturi size, especially if you are using a single plane intake manifold. Even this carb could benefit by machining a step in the booster for street use when using any intake manifold without heat.

A 1.4 inch venturi carb with dogleg boosters will work properly at lower rpm in street use.

When you go to a larger venturi carb of 1.5 inches (or larger) for street use , booster signal will need to be increased by means of an annular booster in order to provide a good signal at lower airflow (rpm).

The days of custom performance carbs built/tuned for true street use is nearly gone.
Custom carb builders are more orientated to race carbs .
Race carbs do not have to operate in the rpm range of a street carb.

We may be surprised how well this carb turns out if you continue. At least the car will be running and give you time to assess things.
None of this is intended to take away from the help/advice “Tuner “ is giving.
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Re: Holley 950 Ultra HP Carb

Post by 1980RS »

rgalajda wrote: Sun Mar 12, 2023 10:29 am To begin with David Vizard is not wrong about Power Valve selection.
From his book “ Be sure to use a power valve that switches at a lower vacuum than the idle or cruise vacuum” ( Higher of the two )

You have two things going against you . That is not a street cam and that carb with a 1.6 venturi is to large for the street without annular boosters.
If that was my car, the cam would be changed . Probably 231@.050 maximum for the street.

The carb that 1980RS mentioned #80496 950 CFM Classic HP is an overrated 850 cfm carb.
Regardless , it is a good carb for the street/strip because of the much smaller venturi size, especially if you are using a single plane intake manifold. Even this carb could benefit by machining a step in the booster for street use when using any intake manifold without heat.

A 1.4 inch venturi carb with dogleg boosters will work properly at lower rpm in street use.

When you go to a larger venturi carb of 1.5 inches (or larger) for street use , booster signal will need to be increased by means of an annular booster in order to provide a good signal at lower airflow (rpm).

The days of custom performance carbs built/tuned for true street use is nearly gone.
Custom carb builders are more orientated to race carbs .
Race carbs do not have to operate in the rpm range of a street carb.

We may be surprised how well this carb turns out if you continue. At least the car will be running and give you time to assess things.
None of this is intended to take away from the help/advice “Tuner “ is giving.
Maybe because this 950 I have is the oldest version it works so well. Only thing I noticed was it has a somewhat rich idle and since the bleeds are not interchangeable it's harder to tune. For me I would just add a T-slot restrictor to fix that. I also have two other carburetors that are like my 950hp and they are the 2 FST 850's. Both have the same main body specs as my 950hp but FST calls theirs 850's. The vs one works great while the DP version I have works like crap, so what did I do with it? well I added new 850hp main body to it. Still need to test it out to get the jetting right and if that doesn't work I just got the 1000 Brawler A/D main body to try out.
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Re: Holley 950 Ultra HP Carb

Post by treyrags »

rgalajda wrote: Sun Mar 12, 2023 10:29 am To begin with David Vizard is not wrong about Power Valve selection.
From his book “ Be sure to use a power valve that switches at a lower vacuum than the idle or cruise vacuum”
Again wrong. At IDLE fuel will not be drawn up the main well through the booster unless your idle is ridiculously high. So it makes no difference if your PV is open or closed - at idle. As soon as the engine comes off idle the intake vacuum increases closing the PV (if it was open).
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Re: Holley 950 Ultra HP Carb

Post by rgalajda »

treyrags wrote: Sun Mar 12, 2023 12:04 pm
rgalajda wrote: Sun Mar 12, 2023 10:29 am To begin with David Vizard is not wrong about Power Valve selection.
From his book “ Be sure to use a power valve that switches at a lower vacuum than the idle or cruise vacuum”
Again wrong. At IDLE fuel will not be drawn up the main well through the booster unless your idle is ridiculously high. So it makes no difference if your PV is open or closed - at idle. As soon as the engine comes off idle the intake vacuum increases closing the PV (if it was open).
The higher vacuum of the two. If idle vacuum is 8" but cruise vacuum is 12" you can still use an 8" pv
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

Still working on the metering blocks.
Drilling the 6-32, to .033 for the IFRs. Completed.
The 82# front jets I have, while I have to stuck to the #93 rear jets.
In the read, I put in a 1" extension.

I pulled the .073 PVCR bleeds.
The rear I was going to plug along with
a PVCR plug that I didn't know I had, that is good.

I need to drill out the front .070 PVCR bleeds.
I thought these could use 8-32 brass set screws
but I cannot seem to get them to fit. I'll try again.

Mark Whitener, seemed to think I should restrict the
long and large T-slot by drilling tapping and placing
a restriction in there. Not sure of the size though.

QUESTION
Currently I'm running dual braided goodyear rubber fuel lines from the
5 gal fuel can to pump, carb, and regulator and return to can.

I'm not sure what to use to clean that line along with the carb feed lines.
I would use Berrymans, but I don't want to dissolve the rubbers.

I've got a gallon jug of isopropyl OH, but not sure how that would work.
I can squirt ether (starter fluid) through the lines, just not sure how to clean the fuel pump then.
Yes I am replacing the fuel filter feeding the carb.

What have y'all found works best?

Pluggin and chuggin,

--thx Spike
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Re: Holley 950 Ultra HP Carb

Post by Tuner »

You can leave the .073" PVCR and decide what to do about MJ and PVCR after you drive it with the WBO2 and tune the idle circuit and find the MJ size it likes. You may (or may not) end up with a smaller MJ and the PVCR may want to be larger than the .073". Either .070 or .073 are OK as a starting point because you will form an opinion after you drive it and tune it.
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Re: Holley 950 Ultra HP Carb

Post by rgalajda »

Tuner , can you explain why no power valve on the secondary?
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Re: Holley 950 Ultra HP Carb

Post by Tuner »

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?
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

@Tuner, Kind of too late now.

Front Primary Metering block, PVCR & 6.5, .070 installed.
IFR = .033, Main Jet = #82 Jet.

Rear Secondary Metering block PVCR Blocked with .073 restrictions removed.
IFRs = .033 recessed. Long Jet extensions installed with .093 Jets. I didn't
have any .092 jets. My jet kits go from 70 - 80, and 80-90. Some jets
are missing as they are in use. I now have an extra set of #93 jets.

Too many hours laterI can say that it was a real PITA doing those
.070 PVCRs in the front, especially using the shoulder type restrictions.

The .033 were simple as I had some older 6-32 .031s I had made some time ago.
I just drilled them out by hand, holding the set screw in one hand and drill
bit in the other. Then they were set with blue threadlocker, down low where
the two channels come together.

The .070 were another story all together. I ruined a few set screws trying to make some
new ones. Then I realized they were actually 6-32 set screws with a shoulder on them.
Someone suggested (I can't recall who) that I use those and not the unshouldered type
as it's possible for them to go all the way into the cavity. It would be similar to a
"roach motel" they check in but they don't check out.

Again I drilled out some that I had previously removed from another block.
Still had issues until I found this solution:
02.01 Drill-070-PVCRs.jpg
They aren't pretty but they do work, I hope.

QUESTION

I have choice to use either 30cc or 50cc squirter pump. For this engine combo,
which makes the most sense?

The carb came with the 30cc green squirters, might as well put some new ones
back into the carb. Though I am running 42 CI more than stock 454 with larger cam.
I answered that, never mind, unless you think 30cc isn't enough.
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Re: Holley 950 Ultra HP Carb

Post by Tuner »

Rear Secondary Metering block PVCR Blocked with .073 restrictions removed.
IFRs = .033 recessed. Long Jet extensions installed with .093 Jets. I didn't
have any .092 jets. My jet kits go from 70 - 80, and 80-90. Some jets
are missing as they are in use. I now =D> have an extra set of #93 jets.
don't start mixing up stamped jet number with measure diameter. .093 is the diameter of a #80 jet. A #93 jet is probably .105" diameter or close to it.

Just put the dang thing together and drive it, then decide what to do based on the symptoms and WBO2 readings, but don't trust the O2 if it misfires, in that case trust your intuition. .
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Re: Holley 950 Ultra HP Carb

Post by USMC_Spike »

@tuner,

No worries, they were typos. #82 Jet front and a #93 jet rear.
I didn't proof read it, just wanted to post it here.

At the moment the car doesn't drive, I haven't been able to reinstall the fuel tank.
I need to new front tire, as these suffered side wall cracks.

I can idle it and go from there.

First, get the carb back together,
clean out the fuel lines and pump, then reinstall on the engine, get it running.

--thx Spike
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