I had a strange knock/tap sound. It was intermittent but varied with Engine speed. I could not locate the source of the sound.
Then I used a three foot length of garden hose as a stethoscope, with one end against an ear.
It was from back half of the engine.
Off came the head. All fine there. I had already installed the tappet guide hold down kit.
But bore number 2 was scored.
Out came the engine as piston number two had been scoring the cylinder wall. This was shortly after total rebuild by me so perhaps there was a piston diameter to wall clearance problem.
If you have not tried the garden hose stethoscope, it might be worthwhile in terms of pinpointing the location of the noise.
Thanks Dennis, I had the engine professionally rebuilt but I have a borescope so I will look into all of the cylinders and see if any of them are scored. I would think it unlikely since the builder has been building engines for 50 years. But anyone can make a mistake. So you don’t think that the.05 difference in the gap could make that sound if it was on more than one valve?
You will know if the tappet guide is loose and whether the noise is from the cam hitting the tapper back down because the tappet guide will have marks on it where the cam lobe has hit it
Why not record the sound with your mobile video and start with your mobile positioned at back of engine over exhaust cam and move it slowly along exhaust cam to front, then move down to front of engine where the breather comes out
On a similar note, when I drive my car, I can hear a tapping from engine at about 1700 rpm which goes away above or below that rpm
I had checked the tappet guides and none of them were loose. The buckets themselves had no play side to side and seem to fit quite well. I actually have a stethoscope that I could use but it was difficult to locate the tapping sound exactly so I was still a little confused that is what led me to believe that maybe it is more than one valve making the sound more specifically the ones that are about double the recommended gap.
A while back I had the head rebuilt and upon installation, I had a loud tapping noise. Paul had pointed me in the right direction when he asked if the valve shims rocked. One of them did not and that was the source of the tapping. If shims lie flat there is a gap between the shim and valve stem that creates tapping.
Glenn
No, 0.009" clearance, by itself, will make NO difference in the tappet noise level. Valve clearances have to be MASSIVELY too large to cause significantly louder tappet noise. Early cars have 0.004/0.006" clearances and later ones 0.012-0.014", yet they sound exactly the same (ignoring the very different high RPM sound with the much later parabolic cams). The primary source of tappet noise is the tappets shifting back and forth in the guides in response to the forces imparted by the cams rotation.
Replace the tappets and/or guides, as needed, to achieve correct, close tappet to guide clearance, and the engine will be quiet.