I have found a very quick and accurate way of measuring the spring installed height on DOHC heads that don’t have enough room to use a spring height mic. I made a simple but precise piece of tubing on the lathe that I use as a standard. It’s important to measure accurately, especially if you’re pushing the springs to their limits. In this case, the standard was 1.100”. I level up the guide I’m going to check in my seat and guide machine. I put the valve in, slip the standard over the valve, then put the retainer and locks in. I then use a piece of Delrin composite to tap on the valve tip and fully seat the keepers into the retainers. I then put an indicator directly over the valve tip and zero it with the retainer sitting on the standard. I push the valve up to the seat and read the travel on the indicator. In this example, my travel was .354”. 1.100” + .354” = 1.454”. Subtracting the top hat seal bottom flange of .035” and I came up with 1.419” available installed height. I ended up with the absolute minimum coil bind clearance, which is why it’s so important to check every setup.
Jake Sampson
Sampson Racing Engines
Inver Grove Heights, MN
