Kinsler_Handbook_#32 December 2017

Kinsler Fuel Injection, Inc, 1834 THUNDERBIRD TROY, MICHIGAN 48084 U.S.A. Phone (248) 362-1145 Fax (248) 362-1032 55 THROTTLE SHAFTS We make out throttle shafts from special stress-proof steel, which makes them unusually strong and tough. We hard nickel coat them for excellent wear resistance, then bake them to eliminate any embrittlement. MATERIAL FOR THROTTLE SHAFTS We use 3/8” diameter milled type shafts because they make a better bearing than a 5/16” does and we get more strength than 5/16” with less air flow resistance! How? A) 5/16” has so little cross-sectional area that it is usually slotted for anything larger than 2” throttle bores. The place where the the throttle plate screw goes is very weak, as the #8 screw hole removes most of the remaining material! B) A milled 3/8” shaft has 24% more cross-section after the #8 screw hole is tapped into it than a 5/16” slotted shaft. C) The 5/16” shaft presents a .312” wide restriction to the airflow. The milled 3/8” shaft is .188” wide after milling, plus .071” widthof the throttle plate= .259” total,which is 17%lesswidth than the 5/16” slotted shaft. D) BACK-CUT The milled 3/8” shaft is strong enough that we canmill aflat on the backside of it .062” deep and stillmaintain good strength. This leaves .126” shaft width, plus the .071” plate width = .197” total, which is 37% less width than the 5/16” slotted shaft! This is optional on all our units and replacement shafts. E) STREAMLINED The ultimate shaft for air flow is the back-cut shaft with it’s leading and trailing edges machined with a radius from the OD of the shaft to the flat area of the back-cut. It is then blended and polished. This gives an improved aerodynamic shape. This is optional on all our units and replacement shafts. © 2017 WE MAKE THE STRONGEST THROTTLE SHAFTS IN THE INDUSTRY We can make custom shafts to your print or sample. THROTTLE SHAFT BASICS Alternate Material 303 stainless steel for salt water marine use. These won’t rust, but they are only 1/4 as strong as the stress proof steel, and wear much quicker. Don’t use this material unless you really feel you need to. Style Milled A flat is machined halfway through the shaft for the throttle plate. Slit A slit is cut through the middle of the shaft, leaving the shaft at it’s full diameter. Machining Each end of our flat for the throttle plate has a .010” radius to prevent a stress riser. We also break the edge of the two outside corners at each end of the flat. On our shafts with multiple throttle plates we are careful to machine all the flats exactly at the same angle and plane. If the flats are not cut properly, the idle air distribution and part throttle operation will be poor. DIAMETER MATERIAL 4760 5/16" (.312") Stress proof steel 4761 3/8" (.375") Stress proof steel 5452 5/16" (.312") 303 stainless steel 5453 3/8" (.375") 303 stainless steel Milled shaft Slit shaft Back-cut shaft Streamlined shaft Shown Actual Size Ray Price’s Kinsler injected top fuel Harley Davidson drag bike Jason Meyer’s Kinsler injected WoO sprint car