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To look at your post backwards, yes, try the 15 thou gaps and if it remains clattery when hot then you can tighten them up one thou at a time until it stops. A tappy tappet is a happy tappet, as they say! It is a MG metro engine after all. You could also use compression test to see what changes come about as you do it. You want peak compression to be sure the valves are opening and closing properly.Whole bodyshell is like new after the rebuild.
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I have an MOT scheduled for tomorrow.
Interestingly, I took it out today and in the first part of my journey I had to turn left and then up a steep hill, it lacked power and we got the pre-detonation in the inlet side. I pulled the choke out and we regained power and stormed up the hill.
This led me to think it was under-fuelling. So I have tweaked the jet down a smidge and will try the same trick tomorrow.
One other mystery is what the valve clearances should really be. One school of thought says ALL A+ engines 12 in/12 Out but the Vizard-Wizard book has a table saying the Metro engine with std rockers should be 15 in and 15 out.
Now as I cannot identify what engine this is for certain, what should I do?
Try 15/15 and if it is a clattery bucket of bolts put it back to 12/12?
I am now wondering if you haven't got a little bit too much advance coming from the vacuum. When driving uphill with your foot flat on the gas, it'll advance like that, which is what you were doing. BUT do make sure you do the tappets first. If your tappets are a bit tight then the inlet valves could be open too long which could mean that is why you are getting the pre-detonation.
If that doesn't stop it, try just disconnecting the vacuum tube and seeing how it goes without it. I doubt it'll continue to pink, if pinking is what it is doing.
I don't think continuing to richen it is the answer. You could do plug cuts to check how rich the mixture is.
But you have got enough to be going on with. You are very close to having it right.
