Engine noise

[53lake]

Perhaps someone can help me identify an unusual engine noise on my 1968 Traveller with original 1098 engine.

The engine was rebuilt at a local shop here in the USA (but not a British engine specialist). I supplied all the parts they needed from ESM, and the Haynes manual. New rings, bearings, seals, timing chain and gears, camshaft, valve guides, followers, oil pump. Added electronic ignition. They had no test bed at the shop, and I was working on the rest of the car, so it wasn't run until I put it in back home. I did check the valve stem clearances were at 12 thou.

It seemed to run fairly smoothly on start-up, then this noise developed which I don't like the sound of.

Hopefully, I’ve attached a youtube link of the sound, with engine fully warmed up.
https://youtu.be/wgZzXcfF01s

It sounds like a metallic clacking, similar to pre-ignition. It is hardly noticeable on cold start-up, but worsens on the run-up to operating temperature. It is most evident just as the revs increase from idle. Then at idle, it is intermittent. At higher revs it appears to fade (but might just be drowned out by the overall noise, can't really tell). It seems to come from the front of the engine, but not certain though.

I’ve removed the fan belt, and eliminated the water pump or dynamo as the source. I’ve put a long screwdriver to the ear on the timing chain cover, but that isn’t the source.

I’ve got the ignition timing set per manual at 3 deg BTDC at below 400 rpm idle with a strobe. Advancing or retarding the timing with the micrometer screw makes no difference to this noise. The mixture seems OK, the plug deposits are a nice gray, and there is no visible exhaust. I’m running on ethanol-free gas only. But the engine noise I’m trying to trace sounds very metallic, rather than a combustion problem.

I’m a bit nervous about tackling any longer trips in case I’m damaging something. If I have to go back to the shop that overhauled the engine, I’d prefer first to have an idea what the problem might be.

Any thoughts most welcome – thanks.

[kevin s]

Unfortunately that sounds to me like the piston or conrod are hitting something, your only real option is to take it apart and check for clearances and witness marks.

You can take the head and sump off then remove the pistons / rods with the engine in the car.

[simmitc]

Can you use a stethoscope or even a piece of wood to listen to different parts of the engine so that you can track down where the noise originates? This would give a clue, but beware of moving parts. From what I can see/hear, the noise is present only when increasing the speed, and not at idle; so there are a few possibilities.

[Monty-4]

From the video it sounds more pronounced when opening the throttle/accelerating?

I'd take a peek at the timing chain before removing the head and/or dropping the sump in case the old screwdriver trick isn't picking the noise up. Is the distributor gear and plate tightened down correctly?

[53lake]

Thanks all for the constructive suggestions.
Yes, Monty-4, it is mostly noticeable while just starting to rev from idle, then it fades. When idling I hear it only intermittently.
I'd have thought if something was fouling in the piston/conrod dept I'd hear it as a regular impact increasing with engine revs.
Distributor is tightly clamped. Will definitely try the stethoscope test, and check the timing chain. I have a slight leak from the cover, so that needs to come off anyway.
Thanks again!