Top end noise

[Rocketman1955]

Was source of the top end noise ever identified?
I have an engine with a similar issue - loud tap from the top of a cylinder hot or coldf.
Obvious suspects were worn small end or wide tappets.
Tappet check revealed an exhaust at 19thou ins., others also wide.
All were reset to 8thou ins. as per maximum in Haynes manual.
Engine was then really quiet, eliminating a small end problem.
However, I had used the classic adjusting sequence for each cylinder:
exhaust fully open, adjust inlet
inlet open, adjust exhaust
I then read that sequence can result in tappets being too tight, so I checked and 3 of them were.
So reset the Citroen way: cyl 1 inlet open, adjust cyl2 inlet, etc.
Engine then got a bit noisy again
This where it gets interesting – being an imperialist I had used the gaps quoted by Haynes at 6 to 8 thou ins. These gaps do not equate to the Haynes metric spec of 0.15-0.2mm.
The conversion to imperial gives 3.8 to 5.1thou ins. So assuming the quoted metric gaps are correct my engine is running with about twice the specified gap.
Next step to reduce the gaps and see if the engine gets quieter and also follow up on any other ideas from this thread!

[Rocketman1955]

Oops-Haynes metric to imperial is correct!
Calculator operator failure…..

[Rocketman1955]

Following Ian's entry from May-2024, I also set the clearances to the minimum 6 thou rather than 'safer' maximum 8 thou.
Purists might say the wider gap of 8 thou is safer as valves will not be held open, but 6 thou is the quoted minimum and should be adequate for normal road use.
The difference in tappet noise was very apparent and surprising - like a bag of nails converted to a sewing machine!
Maybe the head material and design amplifiy the tappet noise?
Obviously other engines may have other noise root causes, but minimising tappet clearance is an easy test.
Mine are staying at 6 thou!

[Ken Hanna]

Rocketman,
since you've decided to set the rocker clearances at the minimum value of 0.15mm, probably best to check them regularly, as they will close up with use and the last thing you want is burnt valves which will happen if they've been held off their seats.
Since unleaded fuel was introduced in the UK, I've always I've always set valve clearances at 0.25mm, using 'slack fit' for the exhausts and 'sliding' for the inlets, as some of my customers were covering up to 20,000 miles per year..
.

Obviously other engines may have other noise root causes, but minimising tappet clearance is an easy test.
Mine are staying at 6 thou!