Engine vaccum - 90' Suburban
 

Does anyone know what the engine vacuum should be pulling at idle, at sea level? Im trying to solve a puff from my exhaust, and checking the vacuum for a possible intake leak, but cant find anything on the web for what the factory vaccum reading should be. At the moment the engine is pulling 18psi at operating temp in park. Thanks!

Re: Engine vaccum - 90' Suburban
 

18psi is in the right neighborhood especially considering its likely the engine is at least worn some. When does the puff happen and what color is it? Most of the time a puff from exhaust in a sbc is valve seals.

Re: Engine vaccum - 90' Suburban
 

18" hg is perfectly acceptable. Is it steady? What is your ignition timing set at?

Re: Engine vaccum - 90' Suburban
 

Thanks for the replies. The timing is set 4 degree's advanced. The vacuum is steady, doesn't pulse or jump around. And the muff is more noticeable at idle. I do think some of the valve steam seals are going, because on cold starts, it has a blue puff of smoke out the tail pipe, but doesnt smoke while driving. or consume oil.