Product Summary

Universal Fit, 3.70" Overall Thickness, Steel

  • Compact for installation under floor or on firewall of almost any vehicle
  • Single diaphragm booster measures 7" in diameter and fits in the tightest spaces possible
  • Booster has four bolts on 3 3/8" centers which fits a variety of mounting brackets and pedal assemblies
  • The length 4 bolt mounting face to master cylinder mount face is 3-5/8"
  • Zinc plated for corrosion resistance

Key Specs

MFG. Part #91031430
BrandSpeedway Motors

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Single diaphragm boosters are compact for installation under floor or on firewall of almost any vehicle. Booster measures only 7" in diameter. Zinc chromate finish. The single diaphragm is usually used on lighter vehicles. In the heavier applications of 3000-3500 pounds or more we normally use the dual diaphragm boosters.

You will need full manifold vacuum available to the booster. Manufacturer requirements vary between 18 and 20 inches of vacuum. With radical cams there are many cases where there is a loss of the necessary vacuum and the only option is a 12 volt vacuum pump available from Speedway under part number 91028146.

  • O.D. is 7" Length from mount surface to master cylinder mount surface is 3-5/8" (this does not include the shoulder that extends into the master cylinder)
  • 3/8 x 24 thread pushrod that is 4" long from mount surface to end of the threads (pushrod nut included)
  • 4 bolt mount pattern on 3-3/8" centers
  • Mount bolts are 5/16 x 20 and 7/8" long and nuts are included
  • Master cylinder mount studs are 3/8 x 18 and 1-1/16" long and 3-3/8" on center

Learn more about selecting the proper brake booster for your vehicle by reading our tech article.Brake System Selection.



MFG. Part #91031430
BrandSpeedway Motors
Overall Thickness3.70"
Outside Diameter7"
Bolt Hole Pattern3.38" x 3.38"
Centerline of Holes3.38"
Material TypeSteel
FinishZinc Plated
Sold in QuantityEach
NotesLength from mount face to M.C. mount face is 3-5/8". Pushrod extends 4" from mount face and has 3/8"-24 threads. Mount bolts are 5/16"-20 x 7/8". M.C. mount studs are 3/8"-18 x 1-1/16".
Brake Booster TypeVacuum Diaphragm Single