Help identify engine noise
 

I’ve got an engine noise I would describe somewhere between a tap and a knock. It is only audible when the engine is warm. It seems to be coming from the intake side of the valve covers between cyl 5-6. It is noticeable down on the exhaust side as well, but not as loud. I’m not sure if it is just “echoing” down that way. It does increase with RPM. Engine otherwise starts and runs fine. No smoking. I thought at first it was an out of spec valve. I did a valve adjustment. I checked all of the valves beforehand and all seemed to be within spec. I went ahead and adjusted all to spec using the kirk tool. Afterwards I noticed no difference in the sound. For what its worth, I changed the oil at the same time. Oil looked great no glitter or metal. I’m wondering if the rocker arm bushing or shaft is worn? I’m kicking myself for not checking that while I was in there. I took two videos. First video is engine cold, just after start up. Second video is after driving, engine oil temp was 180F.

Vid 1: https://youtube.com/shorts/dj3G4Gqpusk?feature=shared

Vid 2: https://youtube.com/shorts/a6husDr5nkI?feature=shared

More info: Did this occur suddenly or gradually? Over how long a period did it develop? How many miles are on the engine? Does it change when you are driving, or can you hear it when you are driving? One other thing to check for when you have the valve covers off: Loose or pulled head studs.

First impression: It sounds like valve tap to me, but of course, it's hard to tell from a recording. Often hard to tell in person too. :)

yup ,,if you did the valve adjustment correctly i would look into the worn out rocker arm bushing or the shaft-but the shaft usually not the problem--it is easy since it is right intake side
Ivan

I would say gradual. Possibly been there several months. Its difficult because you can only hear it if you are listening for it. You can’t hear it in the car at idle or when driving. Only when standing outside behind/beside the engine while it is running. I did check the head stud cap nuts when adjusting the valves. All were tight.

Engine has 130k. I forgot to mention that it had a top end rebuild under the previous owner at just over 100k miles.

To be honest, to me; it doesn't sound bad at all, these engines make all kinds of funny little noises as things wear, also remember; air cooled engine don't have the luxury of the water jackets that tend to damp many of the little noises internal combustion engines naturally make.
Just my ramblings.
Ant.

I would keep driving it. As ant7 said, these engines often make noise.

My engine actually sounds the same. No noise when starting cold, then this moderate ticking noise when warm. Though one ticking is louder than the others and can even be slightly heard in the cabin at idle speed if listening carefully.
I was also kind of worried and so I recorded two videos and sent them to Ivan a few months ago and he said it's OK, may be do a valve job some time.
I'll drive it until it's time to do the next valve job. Car is running like a charm.

I've posed the question on this forum before as to whether valve clearances increase when the engine is hot, and the response from several of the builders and racers is that they increase. I know from setting my valves with several different methods, that it doesn't take much increase in valve clearance to get valve noise. If you are greater than about .005 cold clearance, you will get valve noise when it's warm. Unless gets louder than what I heard on the video, it sounds normal.

BTW, several other guys here and I set valves the easiest way possible--no screwing around with feeler gaugers, snap-gaps, Stomski tools, etc. Instead, we screw the adjuster down to contact, then back it off 1/10 turn. That gives .004" clearance. 1/8 turn gives .005" clearance, if you want to be on the safe side, but it does increase valve noise.

Thanks for the insight. You’ve put my mind at ease. I will keep an eye on it, but for now I will stop worrying and drive it.

yup,as PeteKz said... i do it like this past 40 years;-)
Ivan
https://www.youtube.com/watch?v=O_ypBn_u7g8

Simple! :)
Ant.