Black car has suddenly developed an engine noise when starting from cold. Thought I'd make it interesting, so I'm prepared to reward the successful, or closest guesser with a bottle of half decent Red or a 6 pack of ale. The prize will be awarded at Summer Camp!
The noise is best heard on the vid if you have half-decent speakers on your computer. If you don't it just sounds like a tinny tappet rattle.
I'd describe it as a whoop whoop noise coupled with a noisy tappet noise. Sounds like a Chinook helicopter doing a tight turn, if that helps!
The noise goes away once engine is warm. Does it on petrol or LPG.
Video is here.
Enjoy the lovely Devon views as you put your engineers ears on!

Heard the noise. Headed to Google. Wished I hadn't.

It's like looking up your symptoms when you're not feeling well - look long enough and you'll be convinced you'll die tomorrow of advanced cancer.

On the plus side, looks like you live in a very nice place.

Blow out the side of one of the head gaskets just starting?

I don't think its got cancer, or at least I hope not!
HG- I think you might be getting warm Gordon. No misfires logged on Nano run, no coolant loss, no water in oil. When last leak-down checked (around 200 miles ago) no leak down issues. Compressions checked at same time. all 160 ish with no great variations between pots.
I'm really hoping its not HG though. Blue one's already in the operating theatre for HGs.

Funny, you mention Chinook and in the sidebar appear all adverts of Chinook vids.
As I can hear it with my android tablet in Le Havre you are missing some (one or more) cylinders.
Or else give us the answer and I will pay the ale.

Got it! Ignition coil on its way out. At least part of it.

Not warm yet Tony- coils are new, Nano is not reporting any missing cylinders. I can't give the answer yet though, 'cos I don't know :)
Edit- I do know that I can't keep up with the maintenance needed to keep even one of these things on the road at the moment. Workshop currently full of- TR6 halfway through restoration, blue P38 for head job and a Defender for some rust repair. No room at the inn for the black one :(

What's the sputtering then Mark, must be some pot missing. Dit you check the plugcaps? (With a glove)

If it was missing, it'd show on the Nano "cylinder missfires" log. There would also be something in the "roughness" log. Nothing recorded.
I was thinking perhaps a cracked exhaust manifold. Gap heals itself when engine warms up.

But does Nano report misfire when there is ignition but no combustion?
I trust my ears, even on a small tablet. A bad plug may also works again when engine hot.

I trust your ears too! Mine agree with you!
The engine is as smooth as a smooth thing. You could balance a coin on the rocker cover (in theory)
As far as Nano and the missfire, from the Bosch SID:

Misfire detection
Legislation requires that the ECM must be able to detect the presence of an engine misfire. It must be able to detect misfires at two separate levels. The first level is a misfire that could lead to the vehicle emissions exceeding 1.5 times the allowable levels for this engine. The second
level is a misfire that may cause catalyst damage.
The ECM monitors the number of misfire occurrences within two engine speed ranges. If the ECM detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive ‘journeys’, the ECM will illuminate the MIL. The ECM will also
record details of the engine speed, engine load and engine coolant temperature. In addition, the ECM monitors the number of misfire occurrences that happen in a ‘window’ of 200 engine revolutions. The misfire occurrences are assigned a ‘weighting’ of the likely impact to the catalysts. If the number of misfires exceeds a certain value, the ECM stores catalyst-damaging fault codes, along with the engine rpm, engine load and engine coolant temperature. It will also flash the MIL lamp until the misfires no longer exceed the predetermined number. After the flashing stops, the ECM will continue to illuminate the MIL lamp until the fault is rectified.
The signal from the crankshaft position sensor indicates how fast the poles on the flywheel are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The ECM can detect variations in flywheel speed by monitoring the sine wave signal supplied by the
crankshaft position sensor.
By assessing this signal, the ECM can detect the presence of an engine misfire. At this time, the ECM will assess the amount of ‘variation’ in the signal received from the crankshaft position sensor and assigns a ‘roughness’ value to it. This roughness value can be viewed within the
real time monitoring feature, using TestBook. The ECM will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. The ECM can assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring).:

Just done a full run on the Nano- no faults logged except:
NANOCOM - MOTRP38.APP - MOTRONIC fault file

P1000 = LAMBDA SENSOR UPSTREAM
CATALYST BANK 2 DRIVE CYCLE C
OCCURED 19 TIMES
SIGNAL MISSING
FAULT IS NOT CURRENTLY PRESENT
FAULT DETERMINED AS INTERMITTENT
FAULT CAUSES THE MIL LAMP
ACTIVATION

P0155 = LAMBDA SENSOR HEATER UPSTREAM
CATALYST BANK 2 DRIVE CYCLE C
OCCURED 4 TIMES
SIGNAL TOO LOW
FAULT IS NOT CURRENTLY PRESENT
FAULT DETERMINED AS INTERMITTENT
FAULT CAUSES THE MIL LAMP
ACTIVATION

Just out of interest, having just done a standing run with Nano:
Idle to 2000 rpm then back to idle, zero misfires recorded BUT "roughness" on Bank 1 generally and especially when dropping back from 2000 rpm to idle is higher than Bank 2:

Exhaust manifold blow, either at the manifold to head joint or a crack in the manifold itself. When it gets hot it expands and closes up the gap. From the roughness graphs, on bank 1. What are the fuel trims and lambda sensor outputs like on that bank? Any difference between banks? An exhaust blow would affect the lambda reading so the trims would differ between banks.

It does sound suspiciously similar to mine when it had a blow into the Vee from one cylinder but that meant one cylinder wasn't firing so it was immediately noticeable (and running not smooth at all). Simple test for that is to take the oil filler cap off, if it gets much noisier, then you'll know. However, I can't see it being anything more serious than a manifold blow or it wouldn't be running smoothly which suggests it has to be after combustion has finished.

Bank A is certainly higher:

They don't make a lot of sense?? Both banks are showing rich, although Bank A is the richer of the two, yet the Bank A trim is going above 1 suggesting it is trying to richen further while Bank B is going below 1. I'm assuming a figure above 1 is richening the mixture and below 1 is leaning it off (the readings on a GEMS are shown as a positive or negative percentage). It would be expected that a manifold leak would introduce extra air so the lambda sensor would see this as excess oxygen in the exhaust which would make it appear to be running lean and not rich.

I'm with you on exhaust manifold blow, makes sense that once it's hot it stops,, I've had HGs that sound similar, blowing into centre of engine, but they didn't stop when engine was warm,, easy to check, open the oil cap when running..

Oh well. Unfortunately I think I've found the answer.
Gordon, Gilbertd and Chris share the prize. Blow into centre V I believe. Pushing oil out from back of valley gasket and, the clincher, took off filler cap and it was like an extra exhaust pipe! Video here, but you can't really hear it due to fan noise.
Trust me- it's really chuffing vapour through the filler cap.
Sh!t and double sh!t. Another set of heads to do. Best crack on and finish the blue one...
EDIT- V8Devs at £495/pair looks attractive at the moment. No time to bugger around refurbing/ machining/ fettling existing ones.

When mine did that, it refused to work on gas,, was a bit worrying when it cut out at a busy junction
Blew two cylinders both about 8mm wide, sounded like a rough lawn mower

That's the strange thing. Mine runs fine. Gas, Petrol. No overheating, no problems.
Same with the blue one. No overheating or misfires. Just a sump full of milkshake. Doing diagnostics on the blue one currently. Dropped my leakdown tester so awating a new gauge for that, but will do comp test and sniff test tomorrow.
Pretty innit?!