Well I finally got around to adjusting the valve clearances the other day and it was pretty straightforward. The existing plastic gasket was fine and hadn't hardened but I replaced it with a new one anyway. The two nuts holding down the rocker box were (once I'd cleaned them up) flanged copper nuts rather than knurled nuts I'd seen in Haynes. The inside of the rocker box was filthy with about 3mm thickness of burned on oil and it took 90mins or so in the parts cleaner and scraping with a wooden stick and steel wool to get the insides nice and clean. The top of the head itself was also caked up with carbon but other than to wipe what I could get to with a rag soaked in White Spirit, I reluctantly had to leave it alone as scraping off the deposit would have resulted in some falling down the pushrod holes and find it's way to the oil pump in the sump. Mr Reno recommended adding a litre of diesel to the oil and running this for a week or two as this would loosen up the muck. The Renault Handbook specifically mentions NOT to use flushing oil.
I removed the plugs after marking the plug leads 1 to 4 as this made turning the engine over easier. Rather than jacking the car up, putting it into 4th gear and turning one of the front wheels, I put a socket onto the crankshaft pulley nut yet I still found it a little difficult to detect when a rocker was fully down.
Haynes specifically warns against using pliers and to use two spanners. The locking nuts are 10mm but the heads of the adjusters must be 3mm or 4mm and I didn't have anything small enough. Mr Reno kindly sent me a picture of his valve adjusting tool which would have made life easier. Searching on eBay, there are numerous tools, some of which are expensive, and these are basically a short socket and arm plus a central rod with either a screw driver end or a slot (for our cars) and an adjusting knob. I shall get one for next time.
After cleaning up the rocker box, I gave it a few coats of silver and lacquer, and then proceeded to fit it back to front. Replacing it correctly in amongst the heater hoses and cables resulted in my less-than-pristine silver rocker box having a number of scratches.
The over-engineered sprung loaded throttle cable tensioner then broke send stuff pinging around the workshop. The weakened central plastic guide was already cracked but it was fitting a new e-clip which did the final damage as it was the groove in the plastic which finally gave way. I have replaced this unnecessary device with the threaded adjuster from an old BMW motorcycle brake cable and everything seems fine.
I may have to either shorten the quadrant spring which closes the throttle or fit a stronger one as the tick over could be even lower still even though the tickover screw is backed off and the cable a little slack.
So was the clatter any better? Well every valve was found to be a little loose so I got a little nip on the feeler gauges but I can't really tell the difference. When I took it out for a run yesterday, I turned off my hearing aids and it's pretty quiet now ;-)