Silicone Rubber Port Cast

Here's a cast of the inlet port from the Elder 8-port aluMINIum cylinder head. The process starts by coating the inlet port with a very thin layer of Vaseline, then inserting the valve with just the inner spring to hold it in place. Following the instructions for the rubber, simply pour it into the port, vacuum to remove trapped air, then set it aside for 16 hours. After removing the valve, I push the cast out with the ram of my milling machine using a wooden dowel on the business end. With a moderate amount of effort, the cast extrudes out the throat without damage or distortion.

The silicone rubber material I use is made by and it is supplied by a local plastics shop. It's pretty cheap too, for $40 CND I got enough of the Mold Max 30 to do 20 casts of this size.

Click on each picture below for a closer look. These castings were taken from the first casting that was shipped to me. Because of some disappointing flow data it was sent back and replaced with a new casting that flows much better. The short radius that appears fairly tight here has been widened out considerably.