Quote:
Originally Posted by
marques
Great. But why then would others adjust to the tighter end of the range? As far as I can see this would be counter productive, not only potentially damaging but also shorten the adjustment period?
Are there performance benefits? Again common sense tells me the opposite would be true as the capacity would be reduced?
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I guess one might err on the tighter side of the acceptable range because of wanting a quiet, less "tappety" engine. The risk is, as you suggest, that as the valve seats regress, they will become over-tight sooner as there is no room, or spare capacity to allow for this.
Anywhere within tolerance will not be detrimental to performance, only if the motor runs outside the clearance range will issues occur.
Some of the symptoms associated with tight valves:
They won't close properly, resulting in loss of compression and power and there is a risk of burnt/melted exhaust valves and engine damage. Poor starting and rough running, particularly at tick-over. Worse economy. The top end will run quiet.
Some of the symptoms associated with loose valves:
The valves won't open fully, so exhaust gases won't be scavenged properly on the exhaust stroke and a full charge of fuel/air may not be drawn in on the induction stroke, all meaning a loss of power. Poor running at higher revs. Worse economy. The top end will be noisy.