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Description
850CFM Ultra XP Carburetor - 0-80804HBXOverview: Xtreme Performance Holley Ultra XP carburetors! Ultra XP carbs are up to 38% lighter than our traditional race carbs, have fuel capacity that is 20% greater and 30 other new features! They're available in our all new Hard Core Gray hard coat anodized finish with Black billet for improved corrosion protection. They're also available in natural tumble polished aluminum with your choice of Black or Red metering blocks and base plate. The
Overview:
Xtreme Performance - Holley Ultra XP™ carburetors! Ultra XP carbs are up to 38% lighter than our traditional race carbs, have fuel capacity that is 20% greater and 30 other new features! They're available in our all-new Hard Core Gray™ hard coat anodized finish with Black™ billet for improved corrosion protection. They're also available in natural tumble-polished aluminum with your choice of Black™ or Red™ metering blocks and base plate. The Aluminum Ultra XP comes in 600, 650, 750, 850, and True 950-CFM. Holley Ultra XP carburetors offer new features such as an integrated idle bypass valve that allows for idle adjustments while maintaining the correct throttle plate to transfer slot relationship, high capacity fuel bowls which feature 20% more fuel capacity to eliminate starvation, integrated fuel shelf to minimize fuel aeration and internal baffling to control fuel slosh. Other features include all aluminum construction, fully tunable billet metering blocks, billet base plate, adjustable secondary linkage and knurled (hand adjustable) curb idle screws. Holley Ultra XP carburetors are the ultimate in square bore race carburetors!
Features:
- Aluminum Construction (saves 4.5 lbs - 38% weight savings)
- Hard Core Gray with black anodized billet aluminum metering block and booster inserts
- Designed for use on Drag race, circle track, or any high horsepower engines
- Contoured venturri inlet offers balanced airflow for increased horsepower
- Air bleeds moved outward to allow a smoother transition of airflow from the top of the carburetor into the venturii
- Metering blocks feature improved durability, true gasket sealing and fully adjustable (emulsion bleeds, power valve channel restrictors & idle feed restrictors)
- Integrated idle bypass valve eliminates the need for holes in throttle plates and allows for proper adjustment of idle while maintaining correct throttle plate to transfer slot relationship. Helps maintain good idle control when using radical camshafts.
- Dual 30cc accelerator pumps provide the perfect amount of fuel from idle to full throttle
- Fuel bowls provide 20% more fuel capacity while controlling slosh with internal baffling
- Clear sight windows on both sides of bowls for easy and safe fuel level adjustments
- Built in drain plug in front center of bowl provides easy access to empty contents of bowl
- 8AN (o-ringed) inlet threads offer a large variety of plumbing options and can be plumbed from either side
- 4 corner idle allows you to precisely control your idle system
- Mechanical Secondaries for perfect off the line launches
- Elongated (dual pattern) mounting holes allow fitment on intakes with square flange (Holley 4150™ style) or large flange (Holley Dominator® style)
- Knurled (hand adjustable) primary and secondary curb idle screws allow for easy idle adjustment without the use of tools
- Primary throttle shaft capped to prevent entry of debris & contaminates
- Factory machined accessory mounting hole for easy addition of adjustable primary throttle stop. New secondary pump cam lever designed to provide positive throttle stop on secondary side
- Stainless steel adjustable secondary link. Provides choice of 1:1 or progressivesecondary throttle actuation for ultimate control of secondary opening rate
- Baseplate designed with a boss that can be consumer machined for vacuum source
- Includes notched float and jet extensions
- 100% wet-flow tested by Holley technicians to assure it arrives ready to run!
Application:
| Year | Make | Model | Submodel | Engine Size |
|---|---|---|---|---|
| Universal |
Specs:
| Barrels | 4 |
|---|---|
| Billet Color | Hard Core Gray with Black |
| Booster | Down Leg |
| Brand | Holley |
| Carburetor Use | Professional Race |
| CFM | 850 |
| Choke | None |
| Circuit | 2 |
| Condition | New |
| Emission Code | 3 |
| Finish | Hard Core Gray |
| Fuel | Gasoline |
| Fuel Inlet | Dual |
| Marine Use | No |
| Material | Aluminum |
| Model | 4150 |
| Primary Main Jet | 84 |
| Primary Power Valve | 4.5 |
| Primary Pump Nozzle Size | 32 |
| Product Type | Ultra XP Carburetor |
| Secondaries | Mechanical |
| Secondary Main Jet | 84 |
| Secondary Pump Nozzle Size | 32 |
| Supercharged Application | No |
| Throttle Bore | 1.750 inch |
| Venturii Size | 1.563 inch |
| Warning | California Proposition 65 |
| Warranty | Limited 90 Day |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.2 ★★★★★
Based on 21 reviews
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Product Reviews
★★★★★ 5
Absolute game changer for chronically dry feet/cracked heels
Size: S (up to size 7)-Beige
I had recently bought a pair of silicone heel/ankle wraps to fill out my boot a little since I noticed my heels were lifting when I was skating. I tested them out around the house and noticed they left my heels softer while the rest of my sockless feet got quite dry. So I got these full foot silicone socks to see the effect of having my whole foot covered. I slather the entirety of my feet with Dr. Scholl's Severe Cracked Heel Restoring Balm (love how convenient it is to apply it to my feet with the solid stick form) and then slip them into these silicone socks. After just a couple hours, when I pull out my feet they're (a teeny bit sweaty at first), but then overall soft and smooth and have absorbed the balm fully leaving barely any residue in the silicone sock. I find these silicone socks generally comfortable; I wear them in the evenings while relaxing on the couch, take them off after a couple hours and let my feet breathe a bit, and then reapply my balm and socks and wear them to bed. If I wake up in the middle of the night, which I almost always do (not because of the socks), I'll take the socks off and allow my feet to breathe again. I wear a woman's size 6 shoe and the small size is pretty comfortable. However, I made the mistake of wearing them while being on my feet for a couple hours straight during household chores -- they must've somehow cut off my circulation a bit with the standing, so I wouldn't recommend wearing these silicone socks while being active. And since they're not exactly my foot size, they slide around sometimes and will start to feel tight at my big toe. But if that happens, I just tug on the toe area of the sock to give my big toe more wiggle room and problem solved. Prior to wearing these socks, I was soaking and doing heavy duty exfoliation of my feet every week. These socks seem like they'll work to help me extend the time between soakings and exfoliations. The 5 pack is a great value. So far none have torn, so they seem rather durable. Not sure what I could even do to tear a hole in these.
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Reviewed in the United States on January 16, 2026
★★★★★ 5
Works wonders
Size: M (up to size 9)-Beige
Works wonders for dry feet, like really dry, hard feet.
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Reviewed in the United States on February 23, 2026
★★★★★ 4
EXCELLENT FEET MOISTURE PROTECTION
Size: S (up to size 7)-Beige, Size: S (up to size 7)-Beige
Why did you pick this product vs others?:
I have burns on my feet and needed something that I could put burn creme on and still walk around in with. I tried other silicone footsie but they would teae really easily. So far these are doing really well for this purpose. They are holding their shape too. The only caution I have is the same with all silicone footsies: They can be slippery on wet floors, so also wear with socks over them.
The biggest issues is when they say a size they mean it. The silicone used in these have little give in them, so they won't stretch out and loose their shape. That can be a good thing, or not so good, depending on how well they fit your feet and what your intent is with wearing these. The other issue is if they fit snug around those toes, that tends to be where the first tear in the material will happen. Because of how these are made, the tear is actually more like cracking in the material and once it occurs you won't be able to get much use out of the sock after that. If you are planning to wear them around the house or for long term use, I suggest going up a size or look for the toeless options.
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Reviewed in the United States on July 5, 2025
★★★★★ 3
Silicone socks
Size: M (up to size 9)-Beige
The socks are sized large. The quality of the silicone is good. But they slide around on your feet if you try to walk, making them difficult to use and a bit uncomfortable. Unless you are able to sit for long periods of time the likely will not work well. Recommend looking for a better value.
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Reviewed in the United States on October 27, 2024
★★★★★ 5
Effective
Size: L (up to size 11)-Pink
Fantastic. I put lotion on my feet & wear them when I go to sleep. I often wake up during the night and will remove them to find my feet soft and smooth. They are strong and fit my size 10 womens’ size.
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Reviewed in the United States on March 27, 2026