05-14-2018, 12:10 AM
Clearance is measured with valves fully closed and the lobe not starting to open or just closing. Therefore the lobe of the cam for that valve is ideally 180 degrees from valve full open. You will find that the measurement changes little, if any, if the lobe is only close to 180 degrees, such as 160 to 200 degrees.
Too tight a clearance could lead to a valve not fully closing, allowing escaping exhaust gasses to warp/burn a valve. This is the more serious concern.
Too loose allows the valves to be "hammered", although that may be more of an issue with rocker arms on SOHC, rather than direct cam operation to the valve stems, via shim/bucket on DOHC.
If the lobe is close to raising the valve or just leaving letting springs close it, it will leave a wider gap. That may be audible, although the sound of the fuel injectors is so loud, it may be difficult to hear.
I like to use a stethoscope* to listen to a new motor, which may help detect a change as the miles accumulate.
*A large screwdriver, with blade on the heads and handle to an ear will allow a lot to be heard.
Just my 2 cents
Too tight a clearance could lead to a valve not fully closing, allowing escaping exhaust gasses to warp/burn a valve. This is the more serious concern.
Too loose allows the valves to be "hammered", although that may be more of an issue with rocker arms on SOHC, rather than direct cam operation to the valve stems, via shim/bucket on DOHC.
If the lobe is close to raising the valve or just leaving letting springs close it, it will leave a wider gap. That may be audible, although the sound of the fuel injectors is so loud, it may be difficult to hear.
I like to use a stethoscope* to listen to a new motor, which may help detect a change as the miles accumulate.
*A large screwdriver, with blade on the heads and handle to an ear will allow a lot to be heard.
Just my 2 cents