I rebuilt the carb on my red 202 recently. It's a HJ 3 speed manual with all the pollution control gear.

When driving as the engine approaches 2200 rpm a "chattering" noise starts and gets louder as the revs increase.

It happens in both 2nd and 3rd gear and in third this is around 99-100 km/h.
Of some importance, I feel, is that the noise can only be heard when the engine is under load.
Pressing the accelerator down fully at 80 will give normal acceleration until about 95 km/h when the noise starts.
The noise will also occur when driving along at around 98 km/h and the vehicle goes up a slope, thus loading the engine up.
Also gentle acceleration past 98 km/h will cause the noise to occur, getting louder as the speed approaches 100.
It is possible to hold the throttle at a fixed point and gravity accelerate down a hill to 105 km/h or more without the noise occurring.

I'm self taught so may be missing something completely obvious but if anyone as any ideas about what is happening they would be greatly appreciated.

The fuel level in the carb was within spec, as was the accel pump plunger travel.
The vacuum advance moves the breaker plate when I suck on the vacuum tube so I assume that is working.
The centrifugal advance also looks to be working.
Total advance looks to be around 35 to 40 degrees but this is a visual estimate looking at the harmonic balancer.
Air filter is clean. Getting around 20mm/Hg of vacuum.
New condenser and points were installed. I tried retarding the timing by an additional 3 degrees over standard but this didn't seem to make any difference. I tried setting the points gap/dwell at both ends of the specified range but the noise occurred for both settings.

My gut feeling is some sort of pinging/detonation but I can't work out why it is happening. I have never heard the noise before.
Wild arsed guesses include the fuel pump not supplying enough fuel at high revs, or an air leak somewhere. There is an intermittent tappet noise from the engine occasionally, possibly this may be having some effect.
Hopefully someone will recognise what is happening from the explanation. Remember I'm self-taught, so it could be something really basic.

All advice welcome. TIA.

10/75 from memory(?) but to hope it is in original condition is optimistic.

Should also have mentioned it is a standard single barrel Stromberg.

It has a charcoal canister connected via 4 rubber hoses to the fuel tank, accel pump plunger, vacuum advance line via a T fitting near the carb, and another line to the manifold at the base of the carb which also runs to the top of the rocker cover at the back.
The engine also vents into the air filter from the rocker cover via a short hose.
Brake booster works off the back of the manifold and is working fine.

I will check the manifold bolts too. Thanks.

What's your timing reading at? Not saying it's the problem, but it sounds like pinging. Whack your timing back 5 degrees and do a test run. Then 10 degrees.

Sounds to me like you have a faulty clutch plate.

The intermittent squealing noise when cold may be the throwout bearing.
The clutch plate hub may have suffered damage or wear that has caused the hub to become loose and create a chatter noise.
My mothers EH 149 3spd manual crash n crunch gearbox had a chatter noise in 3rd gear under load above 35MPH, which would disappear when coasting or decelerating.
Dad tried all sorts of things trying to resolve the problem, all the while saying it couldn't be the clutch as he had replaced it not that long ago.
He replaced the uni joints, then replaced the gearbox but the noise was still there. Finally he gave in and pulled the clutch back out and found the hub was loose in the driven plate.
Took the clutch assy back to Repco, they replaced it with another PBR clutch kit and presto the noise was gone.

May not be the same cause as your noise but food for thought.

Edited by user Saturday, 18 January 2020 5:48:27 PM(UTC)  | Reason: Not specified

I suggest you also take this to a reliable mechanic that can fix exhaust problems, a shop I can recommend if you pass by Chatswood is Karl Knudsen Automotive, they fixed my Audi's exhaust problem. They wreck cars as well, if you're into that. Their services is worth their service! http://karlknudsen.com.au

Sandaro, all is good. I still can't work out if 'advancing' the timing is back or forward! It can work either way. It's like 'engaging the clutch'; does that mean pressing down the pedal to disengage the engine from the gearbox or releasing it to lock everything up! Easily confused.

However with heaps of internet access for the last couple of days I managed to listen to a video by a yank with an exhaust manifold leak. It sounded very similar to my noise.

So I rechecked the manifolds. By shoving my head right to the rear of the engine bay I was able to spot a manifold nut I didn't see last time. It was quite loose. And there is black all around it. I've tightened it up and will road test tomorrow. I am optimistic!

EDIT: An update 12 Feb. I tightened the last manifold bolt. The noise is still there but seems to be a bit further up the rev range. A new gasket will go in in the next couple of days.

Edited by user Wednesday, 12 February 2020 1:36:38 PM(UTC)  | Reason: Not specified