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06-23-2008, 11:20 AM
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| Junior Member Join Date: Apr 2006
Posts: 8
 | 1990 Seirra Exhaust I have a question about the heat pipes on my 1990 5.7 GMC engine . Are the pipes that are connected to the exhaust manifolds required ? Looking to put on a set of headers and noticed the stock manifolds had a pipe connect to each one that seems to connect to a vaccum valve/pump. |
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06-23-2008, 12:42 PM
| #2 |
| Senior Member  Join Date: Feb 2008
Posts: 176
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06-26-2008, 06:35 AM
| #3 |
| Senior Member Join Date: Mar 2008 Location: N.Y.
Posts: 1,089
| zo7 its an A.I.R system not an E.G.R system. depends if you need them for state inspection. its an early version of pollution control. the vane pump ads air to the hot exhaust to reduce pollution, called an A.I.R.system. remember when you pull it all off to get a drive belt for a non A.I.R system (not referring to air conditioning). We used to pull the systems off and plug the original manifolds in the 80's |
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