850 CFM - 4150 - Mechanical Secondaries - Hard Core Gray - Gasoline

---

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!

• Aluminum Construction (saves 4.5 lbs - 38% weight savings)
• 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
• Hard Core Gray with black anodized billet aluminum metering block and booster inserts
• 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!
• 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
• Fuel bowls provide 20% more fuel capacity while controlling slosh with internal baffling
• 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
• 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

---

Information:

This carburetor was designed with a dual mounting pattern, so that it can be installed on a manifold machined for a 4150 or 4500 series carburetor.

---

Application Summary:

Year	Make/Model
1962-1973	AC Shelby Cobra
1952-1954	Allard J2X
1954	Allard K3
1952-1954	Allard Monte Carlo
1952-1954	Allard Safari
1960-1974	American Motors Ambassador
1966-1968	American Motors American
1968-1970	American Motors AMX
1961-1962	American Motors Classic
1965-1966	American Motors Classic
1971-1974	American Motors Hornet
1968-1974	American Motors Javelin
1965-1967	American Motors Marlin
1971-1976	American Motors Matador
1969	American Motors Rambler
1961	American Motors Rebel
1967-1968	American Motors Rebel
1970	American Motors Rebel
1966	American Motors Rogue
1962-1965	Apollo GT
1965-1985	Avanti II
1987-1991	Avanti II
1992-1995	Bentley Continental
1965-1969	Bizzarrini GT America
1974	Bricklin SV-1
1961-1963	Bristol 407
1963-1965	Bristol 408
1965-1967	Bristol 409
1967-1969	Bristol 410
1969-1974	Bristol 411
1973-1975	Buick Apollo
1971-1973	Buick Centurion
1954-1958	Buick Century
1973-1981	Buick Century
1959-1989	Buick Electra
1959-1964	Buick Estate Wagon
1970-1983	Buick Estate Wagon
1967	Buick Gran Sport
1970-1972	Buick GS
1968-1969	Buick GS 350
1968-1969	Buick GS 400
1970-1972	Buick GS 455
1959-1963	Buick Invicta
1959-1990	Buick LeSabre
1958	Buick Limited
1973-1987	Buick Regal
1963-1985	Buick Riviera
1952-1958	Buick Roadmaster
1954	Buick Skylark
1961-1972	Buick Skylark
1975-1979	Buick Skylark
1961-1969	Buick Special
1964-1972	Buick Sportwagon
1955-1958	Buick Super
1962-1970	Buick Wildcat
1987-1990	Cadillac Brougham
1965-1976	Cadillac Calais
1952-1984	Cadillac Commercial Chassis
1953-1982	Cadillac DeVille
1953-1978	Cadillac Eldorado
1981-1982	Cadillac Eldorado
1965-1982	Cadillac Fleetwood
1986	Cadillac Fleetwood
1952-1964	Cadillac Series 60 Fleetwood
1952-1964	Cadillac Series 62
1958	Cadillac Series 70 Fleetwood Eldorado
1952-1964	Cadillac Series 75 Fleetwood
1981-1982	Cadillac Seville
1966-1974	Checker Aerobus
1969-1970	Checker Deluxe
1965-1974	Checker Marathon
1977-1979	Checker Marathon