Accuracy of leak down tester / how bad is a leak at the plug

Hi:



I made this simple attachment that allows checking the amount of leakage of a FV head.







At the gauge nominal pressure of 100psi the leak down tester does not show any leak (0%), though I can hear air escaping from the plug hole and, I can see it when I spray liquid on the plug (I will have more questions about this below). Inside the chamber the pressure goes down by about 20psi/s when I shutdown the air supply.

Can these leak down gauges go bad? Or is this just the type of accuracy that one should expect from these tools? I've used this gauge a couple of times (from new), and at some point lent it to one of my competitors. He didn't report that the gauge was not operating properly. How do you check that these gauges operate properly?



The other question is, how bad is a leak at the plug? This plug hole got fixed with a kinsert. I've tried several plugs in this chamber and they all leak. I've added Teflon on the plug threads and it still leaks. I am then assuming that the leak is between the head and the kinsert.

I just soda blasted the heads, I do not know if it was leaking before. Any chances the leak will fix itself as soon as carbon deposit gets overtop the kinsert?

Is this leak of any significance on performance, considering it's not even picked up by the gauge (assuming it's as accurate as it can be)?



Last, I didn't necessarily see any oil on the outside of the plug when I first removed the heads (and the plug).



Thanks,

JS