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Aug 09, 2015 11:21 am
Aug 09, 2015 11:21 am
Subject: Re: Tappet clearances - why the variation?
I discussed that with my friend John (B29) who told me this: the experience was that at least with modern fuels you can give the old cams a bit more overlap but should combine that with 6 thou inlet / 8 thou outlet clearance. I am running this setting at the moment (in combination with a downdraught head). For the improved profiles he recommends 8 / 8.
I only can imagine that optimising the valve timing gives more power, so more heat, therefore requires more gap (which reduces slightly the before increased overlap). Probably one can try anything between 4 and 8 depending on the timing of the cams, but at the risk of burning a valve. Is there a way to find the minimum (cold) gap before burning the valves (0 hot gap) ?
I discussed that with my friend John (B29) who told me this: the experience was that at least with modern fuels you can give the old cams a bit more overlap but should combine that with 6 thou inlet / 8 thou outlet clearance. I am running this setting at the moment (in combination with a downdraught head). For the improved profiles he recommends 8 / 8.
I only can imagine that optimising the valve timing gives more power, so more heat, therefore requires more gap (which reduces slightly the before increased overlap). Probably one can try anything between 4 and 8 depending on the timing of the cams, but at the risk of burning a valve. Is there a way to find the minimum (cold) gap before burning the valves (0 hot gap) ?