I took OCC out yesterday & it drove very well as usual. However, the rattle doesn't go away & before I attempt any fix, with a bit of help I managed to take a very short video in which you can hear the noise...
Have you ruled out gear-lever linkage rattle? Mine rattles, but can be made to stop by applying slight pressure to the gear-lever. It took me a while to find it was the gear-lever that was rattling. The other rattle I have, that I’ve only just worked outage source of, is the bonnet prop. I had an irritating rattle from under the bonnet, it sounded like something loose and metallic. Of course, open the bonnet to investigate and it goes away as the prop is in use. I hope replacing the grommet at the end of the bonnet prop should cure this one!
Thank-you all for your suggestions, which I've yet to try but will do before doing anything more serious.
If I have to go down the little end route, presumably I can do this with the engine in the car? I've already taken the engine & gearbox out once & had some difficulty getting the (early type) gear selection back to good health, so I'm reluctant to do it again so soon.
The engine's only done about 3,000 miles since I rebuilt it (without doing the little ends, of course ) & I changed the clutch, all the seals & most other things then. Might I get away with using the same head gasket?
I realise that I'm going to have to upset the tappet clearances etc, but if I put everything back exactly as it came off, I should be OK.
Then I took the pistons out & found that No. 2 con-rod bearings are absolutely shot after around 3,000 miles (top, compared here to a normal one from No. 3 piston):
On brief examination tonight, the crank journal looks OK. I'm somewhat surprised at the damage & suspect this is the cause of the knocking at high revs as the wear is severe.
I'm going to replace the valve springs & piston gudgeon pins whilst I'm on as I've got the parts handy. I can't feel any play in the little ends, but I might as well do them when everything's apart. Of course, I'll give everything a good check so that hopefully it will be OK when I put it back together....
If the crank doesn't have ridges corresponding to those tramlines then I'd guess that there has been some kind of debris that has got in there, but if the crank is damaged I'd be pretty sure you'd notice it.
PS. I'd still be thinking about measuring the journal how ever good it looks to the eye in view of the short length of time the bearing lasted.
I've had a decent look at the crankshaft journal for No. 2 piston & it has some 'ribs' that match the bearing grooves. They're not massive but the crank will need machining, so it's engine (the remains of...) & gearbox out. I suppose I could take the gearbox off & get to the clutch & flywheel, but it's probably easier to grasp the nettle.
You can just about see the problem:
There is a similar issue with No. 4 although not as pronounced.
The crank is already 10 thou under size, so will have to be taken another 10 or 20 thou. Looking at our vital P6 parts suppliers, I should hopefully be able to get some appropriate bearings.