engine noise

[seniorchristo]

I have been trying to diagnose an engine noise that sounds like clattering valves or a loose timing chain. However I have eliminated these as possibilities and also replaced the lifter sleeves which has reduced but not completely quieted the noise. The noise starts at idle and continues up to about 2000 rpm. It is worse when letting off the accelerator.

I am wondering whether the chain hitting the inner water pump casting could cause a rattling noise? See photo. This photo is from another engine but I see the chain on my engine appears to be rubbing at the same point.

[pharriso]

If the timing chain is hitting that boss then it must be loose...

[seniorchristo]

The chain is not loose. Less than 1/2" up and down movement as specified by Lotus. It is a Dave Bean cartridge style timing case which may however vary from the Lotus unit.

[englishmaninwales]

My aftermarket timing case with a separate water pump (Burton), the casting was inaccurate and required fettling to allow timing chain clearance.

Edit: It was on the opposite side, though, due to an inaccurately placed casting core for the coolant passageway.