- Home »
- Catalog »
- Carburetors & Carb Accessories »
- Holley Carburetors »
- Ultra XP
Ultra XP
Pontiac V8 Ultra XP
Aluminum and Adjustable — Ultra XP for Pontiac V8s
The Holley Ultra XP takes the HP race carburetor and rebuilds it in aluminum. It saves about 4.5 pounds, carries 20 percent more fuel in the bowls, and adds an integrated idle bypass valve that lets you set idle speed without drilling the throttle plates — which is exactly what a low-vacuum Pontiac with a big cam needs.
Butler stocks the 750, 850 and 950 CFM Ultra XP in Hard Core Gray anodized and in shiny polished with black billet, along with the XP-specific dual fuel lines these carburetors require.
Browse Ultra XP Products
Popular Brands:
More About Ultra XP
1. What the Ultra XP Adds Over an HP
Same race intent, better hardware. This is the rung to be on when the engine is serious but the carburetor still has to behave on the way to the staging lanes.
| Idle bypass valve | the headline feature. It lets you adjust idle speed while keeping the correct throttle plate to transfer slot relationship, instead of cracking the blades open or drilling holes in them. With a radical camshaft, that is what keeps idle mixture controllable. |
| Bigger, calmer bowls | 20 percent more fuel capacity, an integrated fuel shelf to cut aeration, and internal baffling to control slosh. Clear sight windows on both sides and a drain plug in the front center of the bowl. |
| Tuning depth | billet metering blocks with fully adjustable emulsion bleeds, power valve channel restrictors and idle feed restrictors. Dual 30cc accelerator pumps, adjustable secondary linkage, knurled curb idle screws you can turn by hand. |
| Weight and airflow | all aluminum construction for a 38 percent weight saving over the original HP, a contoured venturi inlet, and air bleeds moved outward for a smoother transition into the venturi. |
2. Two Install Details People Miss
| It needs its own fuel line. | The XP bowls use -8 O-ring inlets, and the extra bowl depth pushes the inlet spacing out by about .250 inch overall. A standard 4150 dual feed line will not fit. Butler stocks the correct Holley XP lines in both -6 and -8 inlet. |
| Watch the shaker pan. | The XP's large extended float bowls are exactly the ones Butler warns about on drop base shaker assemblies — the radius inside the base may need to be massaged to clear, and a drop base that has been modified is not returnable. Test fit before you cut anything. |
Stocked in 750, 850 and 950 CFM. Before you choose the biggest one on the shelf, note that Butler's own dyno work with the Edelbrock VRS carburetors found smaller VRS sizes matching these on power — airflow rating and made horsepower are not the same conversation.
Not sure what your Pontiac needs?
Email our tech team at tech@butlerperformance.com. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.