inlet manifold vacuum at idle and oil burning

[daverclasper]

Hi. I understand that manifold vacuum is highest at idle?. If so, would any worn inlet valve guides be more prone to sucking more oil into the cylinders at idle, than at higher RPM which has more air being sucked into cylinders, though less manifold vacuum?. Hope this question makes sense?.

Ta, Dave

[johny]

Its always been said that most oil is drawn in through valve guides on overrun. That is drive, throttle off and then accelerate which, if a puff of smoke is produced, indicates worn valve guides ..

[DanMi]

manifold vacuum would be highest when the engine is at high revs but throttle closed, so as Johnny says on overrun

Edited March 7 by DanMi

[Pete Lewis]

Dave yes  vac at idle  around 18-21 inhg     running on light throttle  around 10-12inhg 

on overrun throttle closed  up to 28inhg 

there are no seals on these engines and you do need oil down the guide to lube the valve stems 

there is little oil in the rocker zone unless you have the external oil drench fitted 

so on a worn guide there wont be that much ability to suck volumes of oil down a guide 

as theres normally very little in the rocker zone on a std engine 

good place to make oil smoke is overfilled dash pots ...simple to check 

and never discount contaminated fuel  if its not a continuous  smoker 

Pete

[daverclasper]

Thanks for the info guys

Dave