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Tillotson High Volume (Double Stack, Alky) Fuel Pump Body w/External Pulse
91-1000 Tillotson HR Fuel Pump Body External Pulse - Top
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Tillotson High Volume (Double Stack, Alky) Fuel Pump Body w/External Pulse

Part Number: 91-1000
Online Price: $25.70
Tillotson 91-1000 High Volume (Alky) Fuel Pump Body with External Pulse
Availability: In Stock.

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Description

91-1000 Tillotson High Volume (Double Stack, Alky) Fuel Pump Body w/ External Pulse


The 91-1000 Tillotson High Volume Fuel Pump Body with External Pulse Port is an OEM double-stack pump plate—commonly referred to as a high volume or alky-style fuel pump plate. It is engineered for applications where vacuum signal must be sourced externally rather than through the carburetor flange.


This high volume pump plate is designed to deliver maximum fuel flow for high-performance or methanol-based (alky) setups. It is especially useful in configurations where the intake manifold or carburetor mounting does not allow for a direct vacuum signal from the flange.


Unlike standard fuel plates, this double-stack pump body includes a dedicated external vacuum port, allowing the fuel pump diaphragm to function properly without relying on the flange hole. When converting from a standard flange-pulsed setup to this external version, it is critical to plug the original flange pulse hole to prevent inconsistent fuel pump operation.


Note: If both the flange and external vacuum ports are open simultaneously, it may lead to erratic fuel delivery or poor carburetor performance.

Although most commonly found on HR series Tillotson carburetors, this high-volume pump plate is compatible with any Tillotson double-stack configuration or carburetor that has been converted to use high-volume fuel pump plates.


Key Features:

  • OEM Tillotson part #91-1000
  • High-volume / double-stack / alky-style pump body
  • External vacuum port for non-flange pulse applications
  • Compatible with methanol (alky) and high-demand fuel systems
  • Prevents performance issues in setups lacking flange vacuum
  • Most commonly used on HR-series carburetors
  • Fits any Tillotson carb with high-volume pump plate configuration
  • Durable construction for racing and performance use


Important Installation Notes:

  • Only one pulse source (external or flange) should be used.
  • Always plug the flange vacuum hole when using the external pulse port.
  • Check your carburetor model and plate stack type before ordering.


Common Applications:

  • HR series Tillotson carburetors
  • HL, HW, HB, HM series (when upgraded to high-volume plates)
  • Methanol-fueled karting and racing engines
  • Larger displacement 2-stroke setups
  • Applications where the intake flange vacuum is not available


FAQ

Q1: What is the Tillotson 91-1000 fuel pump body used for?

A: The 91-1000 is a high-volume, double-stack fuel pump plate designed for performance or methanol-fueled (alky) engines. It’s used when an external vacuum source is needed instead of the standard flange vacuum.


Q2: What does "double stack" mean in this context?

A: "Double stack" refers to a two-plate fuel pump assembly(three plates total), offering increased fuel volume for high-demand applications like racing or methanol use. It’s a common upgrade for performance Tillotson carburetors.


Q3: When should I use the external vacuum port?

A: Use the external vacuum port when your intake manifold or carburetor setup doesn’t allow for a pulse signal via the flange. Be sure to plug the original flange pulse hole to avoid inconsistent fuel delivery.


Q4: Is this pump plate compatible with all Tillotson carburetors?

A: It’s primarily designed for HR-series Tillotson carburetors, but it can also be used with HL, HW, HB, or HM models if they’ve been upgraded to use high-volume/double-stack pump plates.


Q5: Can I use both the external and flange vacuum ports?

A: No. Only one pulse source should be used. Having both open at the same time can cause erratic fuel delivery and poor carburetor performance.


Q6: Is this part suitable for methanol (alky) fuel systems?

A: Yes, it’s built for methanol-fueled engines and other high-demand fuel setups. Its design helps maintain consistent fuel delivery in performance applications.


Q7: How do I know if my setup needs this upgrade?

A: If you’re running methanol, a larger displacement 2-stroke, or a racing engine that lacks reliable flange pulse, this part helps maintain fuel flow. It’s especially helpful when using modified or non-standard intakes.

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