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Aug 10, 2015 2:26 pm
Aug 10, 2015 2:26 pm
Subject: Re: Tappet clearances - why the variation?
Thanks for the interest Peter. I'm sure you are correct, the flaw in my assumptions is that the thermal regime is unchanged - it must be the case that the more mixture in, the bigger the bang and the more heat produced. So it will have been perfectly reasonable to play safe and increase the gap, thereby ensuring that the valve definitely closes under all circumstances. This would be especially so as the only penalty would be some increase in noise level and possibly some reduction in power. But to me the recommended doubling from 4 to 8 has an arbitrary look about it and I do wonder whether anyone has bravely tried other settings, whether with standard or high-lift cams.
BTW, these musings were prompted by a recent wedding where the car, an early Rolls, was so quiet that someone nearby wondered whether it was electrically powered. I was a bit envious.
Thanks for the interest Peter. I'm sure you are correct, the flaw in my assumptions is that the thermal regime is unchanged - it must be the case that the more mixture in, the bigger the bang and the more heat produced. So it will have been perfectly reasonable to play safe and increase the gap, thereby ensuring that the valve definitely closes under all circumstances. This would be especially so as the only penalty would be some increase in noise level and possibly some reduction in power. But to me the recommended doubling from 4 to 8 has an arbitrary look about it and I do wonder whether anyone has bravely tried other settings, whether with standard or high-lift cams.
BTW, these musings were prompted by a recent wedding where the car, an early Rolls, was so quiet that someone nearby wondered whether it was electrically powered. I was a bit envious.