Re: Mariner Ticking Noise
The valve clearance is adjusted manually on that engine. As the valve 'train' wears, the clearance generally closes up, so if it starts to make noise, it would not be from increased valve clearance. Unless the 'bucket' surface, or the cam lobe surface has deteriorated, you should not get valve train noise. There just aren't any parts to create a tic.
As noted, an exhaust leak can cause a similar sound, and in a lot of cases would tend to quiet down as the engine warms up and closes up the gap between the head/gasket/manifold.