Re: Annoying rattle

[PGAHOWELLS <PGAHOWELLS@domain.elided>]

Hi
I think chains zizz on start up when they get worn. I have yet to experience
this I am happy to say.
They are supposed to be done each 25k miles, but after 35K from engine build I
have nothing that could be described as zizz on start. Its only on start
because when the oil pressure is up they get stretched out and the zizz goes.
So I think either you have a sticky valve or an incorrect tappet. A sticky
valve doesn't get pulled up fully by the spring, and so the cam gives the
bucket a real slap each time it goes round. Or the tappet gap being too wide
has the same effect. So does the rattle happen five times each second on
tickover. The crankshaft will be doing ten spins a second thats 600 rpm
If all this holds good try some neat Redex in the carb air intakes. It makes a
lot of smoke. (Is it still available, I saw it in Halfords recently)
It will clear gummed up valves. If the valve is rusty, which it might be if
you have started her up for a few minutes every so often in the winter season,
then its head off I guess. ( If you start the car occasionally when laid up
she must be run for twenty minutes at full heat to drive off all the moisture
around the engine etc).  
If the rattle does not go away, then you check the tappets, by taking off
valve cover and sliding a feeler gauge under each one with an upfacing cam.
Rotate engine and write them all down. Its about 16/18 thou for exhaust valves
and 8/10 thou for inlet valves. If one of them is a bit out, then its a quite
a job to adjust, best left to an expert unless you can remove the camshaft. If
it is miles out then suspect rust or worse.
The worst case is that the valve stem is a little bent, causing it to stick a
bit in the guide. 
Whatever you do, my advice is cure that rattle even if it means a head
overhaul. It will be cheaper than some other more horrible possibilities.  
Peter