950 Ultra XP tuning on 500"

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Woodie

Woodie

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Recently picked up a 950 Holley Ultra XP and plan on putting it on a 500" mill. The factory jets are #92 front and rear.. Looking for some advice on where to start. Thanks
 
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Honestly, I know of several instances where those carbs proved very difficult to get dialed in.
I’m talking about the one with the 1.600” venturi.

I’m not going to offer any tuning advice.......but the advice I will give is to buy an o2 a/f gauge so you’re not just running blind.
 
PRH said:
Honestly, I know of several instances where those carbs proved very difficult to get dialed in.
I’m talking about the one with the 1.600” venturi.

I’m not going to offer any tuning advice.......but the advice I will give is to buy an o2 a/f gauge so you’re not just running blind.
Click to expand...
Appreciate your input
 
Woodie said:
Appreciate your input
Click to expand...

Is that the car you have Woody??? The 1.600 Venturi? I've heard the same as PRH but never tuned one yet.

I agree...get an O2 sensor and look at the plugs. Probably start where you are and keep damn meticulous notes so if you get lost you can see where you've been.

Keep us posted. This should be fun.

Wait a minute...92's front and rear??? Is there a power valve in both ends? If so, I'd open the throttle 1:1 and tune it from there.

I'm considering doing that on my carb. I've done 1:1 before and always loved it.
 
yellow rose said:
Is that the car you have Woody??? The 1.600 Venturi? I've heard the same as PRH but never tuned one yet.

I agree...get an O2 sensor and look at the plugs. Probably start where you are and keep damn meticulous notes so if you get lost you can see where you've been.

Keep us posted. This should be fun.

Wait a minute...92's front and rear??? Is there a power valve in both ends? If so, I'd open the throttle 1:1 and tune it from there.

I'm considering doing that on my carb. I've done 1:1 before and always loved it.
Click to expand...
Hey YR, yes it is the 1.60 Venturi. Curious question... What is the benefit of 1.1 on the secondary versus conventional progressive? Here is the spec sheet.

Screenshot_20191010-190840_Chrome.jpg
 
Woodie said:
Hey YR, yes it is the 1.60 Venturi. Curious question... What is the benefit of 1.1 on the secondary versus conventional progressive? Here is the spec sheet.

View attachment 1715406543
Click to expand...


I'm still trying to understand the square jetting without a power valve in the secondary side.

I used 1:1 linkage because with a 4.56 gear it made it so I wasn't so far into the throttle at a cruise. But I had to square jet it and run a power valve in both sides to do it.

I should have written all that crap down at the time. I remember that I could run fairly small main jets and cover it up with the power valve. That was 1985 so I'm taxing my memory on IFR, IAB, PVCR, HSAB etc. I should have written it down.
 
yellow rose said:
Is that the car you have Woody??? The 1.600 Venturi? I've heard the same as PRH but never tuned one yet.

I agree...get an O2 sensor and look at the plugs. Probably start where you are and keep damn meticulous notes so if you get lost you can see where you've been.

Keep us posted. This should be fun.

Wait a minute...92's front and rear??? Is there a power valve in both ends? If so, I'd open the throttle 1:1 and tune it from there.

I'm considering doing that on my carb. I've done 1:1 before and always loved it.
Click to expand...

the dominator that I just put on is 1:1, throttle response is unreal compared to the 850 it replaced!
 
yellow rose said:
I'm still trying to understand the square jetting without a power valve in the secondary side.

I used 1:1 linkage because with a 4.56 gear it made it so I wasn't so far into the throttle at a cruise. But I had to square jet it and run a power valve in both sides to do it.

I should have written all that crap down at the time. I remember that I could run fairly small main jets and cover it up with the power valve. That was 1985 so I'm taxing my memory on IFR, IAB, PVCR, HSAB etc. I should have written it down.
Click to expand...
The HP has 2 power valves..
 
Woodie said:
The HP has 2 power valves..
Click to expand...


Ok, the square jetting makes sense. Without seeing the emulsion and bleed packages I can't say for sure but to me, 92's seem way big to me. I'd also want to know what size the power valve channel restrictors are.

Remember, you cruise on the mains. With staged linkage you only cruise on the primary jets. So those 92's sound HUGE to me. But without seeing the rest of it, it's hard to say.
 
I agree with some previous posters. Install an O2 - A/F gauge and go from there. It looks to rich on paper, but you won't know for sure until you get a gauge on it.
 
My expectation is...... the ootb tune will be quite rich at part throttle cruise....... and will end up lean at WOT.
 
PRH said:
My expectation is...... the ootb tune will be quite rich at part throttle cruise....... and will end up lean at WOT.
Click to expand...


Did you look at the emulsion that carb had? That's sounds like what you see when you have a ton of emulsion. You end up with huge jets to try and keep WOT under control and cruise goes dead rich.
 
My advice on how to tune that carburetor on a 500 is, throw the 950 on the shelf and put a 1050 Dominator on it. The 950 only flows 830 CFM. That ain't near 'nuff.
 
RustyRatRod said:
My advice on how to tune that carburetor on a 500 is, throw the 950 on the shelf and put a 1050 Dominator on it. The 950 only flows 830 CFM. That ain't near 'nuff.
Click to expand...


I've long since lost my understanding of the Holley carb numbering system, but I'm not sure that 1.600 Venturi carb is the 950 that only flows 830. I could be wrong, because like I said, I don't buy Holley stuff. I think the only way that big Venturi could only flow 830 is if it has 1.687 throttle blades or something.

I guess I should get a new Holley catalog so I can look at what they are doing.
 
yellow rose said:
I've long since lost my understanding of the Holley carb numbering system, but I'm not sure that 1.600 Venturi carb is the 950 that only flows 830. I could be wrong, because like I said, I don't buy Holley stuff. I think the only way that big Venturi could only flow 830 is if it has 1.687 throttle blades or something.

I guess I should get a new Holley catalog so I can look at what they are doing.
Click to expand...

Even if it flows 950, that engine needs more than that. I can build a stock stroke 440 that'll suck down a 1250. Putting a 950 on a 500 is like puttin a 2 barrel on a Max Wedge.
 
To YR and Rusy.
Mines a 10.5:1 440 with roller cam, pro systems recommended a 1100 dominator, which is what I ended up getting, seems like those big ol motors like big carbs. As to the drivability, it is a 3 circuit which I’ve read a lot of people don’t like for street use, but idles clean, cruise is real crisp, and instant when you drop the hammer!
 
twayne24365 said:
To YR and Rusy.
Mines a 10.5:1 440 with roller cam, pro systems recommended a 1100 dominator, which is what I ended up getting, seems like those big ol motors like big carbs. As to the drivability, it is a 3 circuit which I’ve read a lot of people don’t like for street use, but idles clean, cruise is real crisp, and instant when you drop the hammer!
Click to expand...
Funny thing is... I literally just got off the phone with Patrick, and ordered a carburetor from them ( Pro Systems) It is a 1050 with Dominator emulsion package. Total cost was 720.00+ shipping of 24.00. I figured since it's a street only car, why not. Patrick had some killer data to share and was very informative, so we will see how it plays out.
 
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