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Yellow bullet has ,IMO,the absolute best forum info there is. LOTS of info you will not see anywhere else. .proper timing and afr can be seen..Bottom line is that detonation and too rich can be seen as loss of ring seal/loss of crankcase vacuum. Of course none of that info means a thing to those not running vac pumps or 3-4 or more scavenge stage dry sumps. What got me to looking deeper into this is the old nascar SB2.2 I'm running. It had a 4 stage pump on it and no vac regulator on a sealed engine. No venting at all yet it had zero evidence of any oil leaks anywhere. Got to asking and it seems the engines drive the pump at a speed that at 9300 rpm is just right for the blowby to be perfectly balanced so as to provide around 20" vac. Cool. Then I ran across this interesting stuff about tuning with crankcase vac readings. I guess it's not really tuning as much as being able to see the engine is happy/not happy with the tune .