Most cylinders have 2 valves: the Intake valve and the Exhaust valve. The Intake valve allows the “clean” air/fuel mixture to come in from the induction system during the first down stroke of the piston. The valve is closed and the “clean” air/fuel is compressed by the piston. The spark plug fires just before the piston reaches its peak and then the air/fuel mixture burns and pushes the piston down. Then, the piston rises and the Exhaust valve opens to expel the waste from combustion. The Intake valves are made of hard materials and are larger than the Exhaust valves to allow for the maximum intake of air. The Exhaust valves are smaller because the exhaust gas is under pressure and ready to move to a low pressure area. The Exhaust valve has to be tougher than the Intake valve because it faces abuse from the corrosive exhaust gases.
It is important that the valves close and seal at the right time so that the cylinder doesn’t lose any air (termed “compression” by mechanics) during the compression stage. It is also important because you don’t want exhaust gas going out of the Intake valve and causing corrosion or ignition of the air/fuel outside of the cylinder (termed a “back-fire”).
My partners and I spent a considerable amount of time grinding the valve face and the valve seat so they will match and create a tight seal. The Intake valve is ground at a 30 degree angle and the Exhaust valve is ground at a 45 degree angle. The valves and seats are ground with an Arkansas stone. (Not sure but our teacher says that they are called Arkansas stones because they are mined in Arkansas!) It was a time consuming process, especially since we had to make sure that the valve was held straight to make a uniform surface. We measured the rotation to 0.001 of an inch!!! Then, we ground the seats to a uniform surface with an electric drill spinning at roughly 10,000 RPM. Voila!!!
We had a fun weekend. We did a number of things but the highlight was when we picked strawberries at a local farm. We ended up with 5 pounds and I bet that Adelina ate an extra pound all by herself. The young girl who gave us our containers told us to sample at our leisure and Adelina took full allowance! I can’t blame her because they are GOOD strawberries.
As you may know, Jessica is training to do a Triathalon Sprint: 300 yard swim, 9 mile bike ride, and a 2 mile run. She is taking a swim class with two other women in preparation for the race. One of the women, Kathy, is a single mom who hasn’t been following Jesus. Jessica spoke with her this last weekend and mentioned that we attend Impact Church. Kathy lit up and said that she had been attending Impact in Saranac (a church plant of the church we attend in an adjoining community) because one of her three daughters has been bugging her to go to church. Kathy is enjoying the church and said that she feels comfortable because the messages are easy to understand and not over her head. We have been praying that God would provide Jessica for opportunities with the women she swims with and God continues to move in our midst! Hallelujah!