Hitman / Race Solutions Dyno / Open Day! 25th Sept
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By Dose Pipe Sutututu · Posted
FWIW, I've aerated oil, and cams snapped. You can figure out the rest 🥲 -
By Murray_Calavera · Posted
Depending on the hose, sometimes engine out is the easiest option -
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Yeah, but look at the margin in viscosity between the 40 and the 60 at 125°C. It is not very large. It is the difference between 7 and 11 cP. Compare that to the viscosity at only 90°C. The viscosity axis is logarithmic. The numbers at 90 are ~15 and ~35. That is about half for the 40 wt oil and <half for the 60. You give up viscosity EXPONENTIALLY as temperature rises. Literally. That is why I declare thicker oil to be a bandaid, and a brittle one at that. Keep the oil temperature under about 110°C and you should be better off. Having said all of that, which remains true as a general principle, if you have indeed lost enough oil from the sump that the pump was seeing slightly aerated oil, then all bets are off. That would of course cause oil pressure to collapse. And 35 psi is a collapse given what you were doing to the engine. Especially if the oil was that hot and viscosity had also collapsed. And I would put money on rod or main bearings being the source of the any noise that registered as knock. Hydraulic lifters should be able to cope with the hotter oil and lower pressure enough to prvent too much high frequency noise, although I am willing to admit it could be the source.
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