Engine vaccum - 90' Suburban - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SoCalSlaughter · 04-23-2014, 06:36 PM

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!

cableguy0 · 04-23-2014, 07:29 PM

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.

Bigdav160 · 04-23-2014, 07:29 PM

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

SoCalSlaughter · 04-28-2014, 12:36 PM

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.

04-23-2014, 06:36 PM	#1
SoCalSlaughter Registered User Join Date: Aug 2010 Location: Ventura Posts: 151	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!

04-23-2014, 07:29 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	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. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-23-2014, 07:29 PM	#3
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: Engine vaccum - 90' Suburban 18" hg is perfectly acceptable. Is it steady? What is your ignition timing set at? __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

04-28-2014, 12:36 PM	#4
SoCalSlaughter Registered User Join Date: Aug 2010 Location: Ventura Posts: 151	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.



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