Scratch LSA please! Its the intake closed point that determines how many degrees of crankshaft rotation you are in compression mode. Stroke and to some amount rod length determine distance in compression mode. Yes hot exhaust contaminating the intake charge can affect cylinder pressure too. However cylinder pressure is mostly affected by the intake closed point. Cylinder pressure affects compression temperature ultimately affecting octane requirement.
Real kicker is exact seat closing points arent advertised. In fact advertised seat timing varies from manufacturers often clouding things trying to compare one brand to another. Area under the curve and valve seat angles play a role here as well as valve timings and lift curves overall on both intake and exhaust.
LSA and ICL are coincidental centerlines of chosen valve timing events. Cams are NOT designed on predetermined LSA or ICL. (though looking at different brands shelf grinds you'd think so)
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Originally Posted by mechanic17
Should camshaft LSA be wide or tight for a Pontiac, and for what purpose (part-throttle cruising? drag racing? dual-purpose? remembering that this is the "Street" section)?
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