dont know **** bout gns
how do you do a leak down test? thanks
Not sure what you are trying to find inside your engine, but to get the best results from a leak down test you should loosen all the rockers so none are touching the valves when rotating the engine. They MUST be completely seated for accurate results.
If you suspect a cylinder or 2 does not have good compression, doing a simpler compression test will find that.
With a low compression reading on a cylinder, you may not be able to determine the exact problem, but if it is low due to head gasket, valve or something else, the head has to be removed for repair reguardless, good luck on what your are doing!