How important is using the proper wall thickness pin for each application?

CP-Carrillo

How important is using the proper wall thickness pin for each application?

It has been a standard practice for years to keep the engines bob weight down by using light thin wall wrist pins. In our experience, this light weight, thin wall is not always best. Not only will thin wall pins cause cracking, they can also cause ring sealing issues.

When the pin flexes two thing happen: the forging is also flexing and that means ring grooves are moving around. You lose ring seal at the floor of the ring groove. This often results in dark rubbing areas by the locks in the pin bores. The pins have been flexing and try to grab the pin hole, plus there is now pressure against the lox as your end play is disappearing.

A simple fix is to focus on making piston lighter and running a heavier wall pin. The pin is like the foundation to your house. It holds everything together to weather the storms that an engine will be going through. This is especially important for engines that have high cylinder combustion spiking -they should have thick wall pins and heavy-duty pistons. For example, a customer will request a 15:1+ compression and wants to run thin wall pins due to revving engine over 8,500 RPM. Understandably but they are not thinking of the cylinder pressure on top of the piston which affects pin, if not thick enough.

Below are some of our general recommended Wall thicknesses per racing application:

  • 400-500HP circle track engine we have seen where a .150 wall works great for this.
  • 800-850HP Sprint car .200 wall DLC pin works great. We have seen where a .170 wall DLC pins work OK in 760 HP engine.
  • Blown LS engine depending on HP power being made and static compression, we would prefer a .200 or .230 wall pin be used. If only making 800HP then a .180 wall pin will work.
  • Naturally aspirated street engine .150 wall pins work well.
  • Big NOS engine, we usually recommend the thickest wall pin we carry.
  • Sport Compact turbo engines, use thickest wall possible unless low HP street engine, then those can be determined at time of order.
  • Blown alky thickest wall possible, as some of these engines make over 3,000HP
  • Naturally aspirated lower HP, lower compression ratio Super stocker of Stock eliminator .150 wall pins is standard.

We carry a variety of materials to choose from to accommodate all your needs:

  • 5100 std bar stock
  • 9310
  • 52100
  • EN39
  • 300M
  • H13
  • 9310 Diamond Like Coated